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• MonoTouch App Crashes When Returning From MFMailComposeViewController

  - by Richard Khan

  My MonoTouch Version Info: Release ID: 20401003 Git revision: 2f1746af36f421d262dcd2b0542ce86b12158f02 Build date: 2010-12-23 23:13:38+0000 The MFMailComposeViewController is displayed and works correctly as a dialog using the following code: if (MFMailComposeViewController.CanSendMail) { MFMailComposeViewController mail; mail = new MFMailComposeViewController (); mail.SetSubject ("Subject Test"); mail.SetMessageBody ("Body Test", false); mail.Finished += HandleMailFinished; this.navigationController.PresentModalViewController (mail, true); } else { new UIAlertView ("Mail Failed", "Mail Failed", null, "OK", null).Show (); } However, once the user selects Cancel | Delete Draft or Cancel | Save Draft or Send, the App throws a run-time error like the following: Stacktrace: at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004 at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr) <0x00004 at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26 at MonoTouch.UIKit.UIApplication.Main (string[]) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31 at MailDialog.Application.Main (string[]) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15 at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr) Native stacktrace: 0 MailDialog 0x000be66f mono_handle_native_sigsegv + 343 1 MailDialog 0x0000e43e mono_sigsegv_signal_handler + 313 2 libSystem.B.dylib 0x903e946b _sigtramp + 43 3 ??? 0xffffffff 0x0 + 4294967295 4 MessageUI 0x01a9f6b7 -[MFMailComposeController _close] + 284 5 UIKit 0x01f682f1 -[UIActionSheet(Private) _buttonClicked:] + 258 6 UIKit 0x01be1a6e -[UIApplication sendAction:to:from:forEvent:] + 119 7 UIKit 0x01c701b5 -[UIControl sendAction:to:forEvent:] + 67 8 UIKit 0x01c72647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527 9 UIKit 0x01c711f4 -[UIControl touchesEnded:withEvent:] + 458 10 UIKit 0x01c060d1 -[UIWindow _sendTouchesForEvent:] + 567 11 UIKit 0x01be737a -[UIApplication sendEvent:] + 447 12 UIKit 0x01bec732 _UIApplicationHandleEvent + 7576 13 GraphicsServices 0x03eb7a36 PurpleEventCallback + 1550 14 CoreFoundation 0x00df9064 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 52 15 CoreFoundation 0x00d596f7 __CFRunLoopDoSource1 + 215 16 CoreFoundation 0x00d56983 __CFRunLoopRun + 979 17 CoreFoundation 0x00d56240 CFRunLoopRunSpecific + 208 18 CoreFoundation 0x00d56161 CFRunLoopRunInMode + 97 19 GraphicsServices 0x03eb6268 GSEventRunModal + 217 20 GraphicsServices 0x03eb632d GSEventRun + 115 21 UIKit 0x01bf042e UIApplicationMain + 1160 22 ??? 0x0a1e4bd9 0x0 + 169757657 23 ??? 0x0a1e4b12 0x0 + 169757458 24 ??? 0x0a1e4515 0x0 + 169755925 25 ??? 0x0a1e4451 0x0 + 169755729 26 ??? 0x0a1e44ac 0x0 + 169755820 27 MailDialog 0x0000e202 mono_jit_runtime_invoke + 1360 28 MailDialog 0x001c92af mono_runtime_invoke + 137 29 MailDialog 0x001caf6b mono_runtime_exec_main + 714 30 MailDialog 0x001ca891 mono_runtime_run_main + 812 31 MailDialog 0x00094fe8 mono_jit_exec + 200 32 MailDialog 0x0027cf05 main + 3494 33 MailDialog 0x00002ca1 _start + 208 34 MailDialog 0x00002bd0 start + 40 Debug info from gdb: warning: Could not find object file "/var/folders/Ny/NyElTwhDGD8kZMqIEeLGXE+++TI/-Tmp-//cc6F1tBs.o" - no debug information available for "template.m". warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(zlib-helper.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Could not open OSO file /Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(gc.x86.42.o) to scan for pubtypes for objfile /Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog Error connecting stdout and stderr (127.0.0.1:10001) warning: .o file "/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)" more recent than executable timestamp in "/Users/rrkhan/Library/Application Support/iPhone Simulator/4.2/Applications/52AF1D24-AADA-48ED-B373-ED08E89E4985/MailDialog.app/MailDialog" warning: Couldn't open object file '/Developer/MonoTouch/SDKs/MonoTouch.iphonesimulator4.2.sdk/usr/lib/libmonotouch.a(monotouch-glue.x86.42.o)' Attaching to process 9992. Reading symbols for shared libraries . done Reading symbols for shared libraries ....................................................................................................................... done 0x9038e459 in read$UNIX2003 () 8 0x903a8a12 in __workq_kernreturn () 7 "WebThread" 0x903830fa in mach_msg_trap () 6 0x903b10a6 in __semwait_signal () 5 0x90383136 in semaphore_wait_trap () 4 0x903830fa in mach_msg_trap () 3 0x903a8a12 in __workq_kernreturn () 2 "com.apple.libdispatch-manager" 0x903a9982 in kevent () * 1 "com.apple.main-thread" 0x9038e459 in read$UNIX2003 () Thread 8 (process 9992): 0 0x903a8a12 in __workq_kernreturn () 1 0x903a8fa8 in _pthread_wqthread () 2 0x903a8bc6 in start_wqthread () Thread 7 (process 9992): 0 0x903830fa in mach_msg_trap () 1 0x90383867 in mach_msg () 2 0x00df94a6 in __CFRunLoopServiceMachPort () 3 0x00d56874 in __CFRunLoopRun () 4 0x00d56240 in CFRunLoopRunSpecific () 5 0x00d56161 in CFRunLoopRunInMode () 6 0x04f7c423 in RunWebThread () 7 0x903b085d in _pthread_start () 8 0x903b06e2 in thread_start () Thread 6 (process 9992): 0 0x903b10a6 in __semwait_signal () 1 0x903dcee5 in nanosleep$UNIX2003 () 2 0x903dce23 in usleep$UNIX2003 () 3 0x0027714c in monotouch_pump_gc () 4 0x903b085d in _pthread_start () 5 0x903b06e2 in thread_start () Thread 5 (process 9992): 0 0x90383136 in semaphore_wait_trap () 1 0x0015ae1d in finalizer_thread (unused=0x0) at ../../../../mono/metadata/gc.c:1026 2 0x002034a3 in start_wrapper (data=0x7b16ba0) at ../../../../mono/metadata/threads.c:661 3 0x002448e2 in thread_start_routine (args=0x8037e34) at ../../../../mono/io-layer/wthreads.c:286 4 0x00274357 in GC_start_routine (arg=0x6ff7f60) at ../../../libgc/pthread_support.c:1390 5 0x903b085d in _pthread_start () 6 0x903b06e2 in thread_start () Thread 4 (process 9992): 0 0x903830fa in mach_msg_trap () 1 0x90383867 in mach_msg () 2 0x0011cc46 in mach_exception_thread (arg=0x0) at ../../../../mono/mini/mini-darwin.c:138 3 0x903b085d in _pthread_start () 4 0x903b06e2 in thread_start () Thread 3 (process 9992): 0 0x903a8a12 in __workq_kernreturn () 1 0x903a8fa8 in _pthread_wqthread () 2 0x903a8bc6 in start_wqthread () Thread 2 (process 9992): 0 0x903a9982 in kevent () 1 0x903aa09c in _dispatch_mgr_invoke () 2 0x903a9559 in _dispatch_queue_invoke () 3 0x903a92fe in _dispatch_worker_thread2 () 4 0x903a8d81 in _pthread_wqthread () 5 0x903a8bc6 in start_wqthread () Thread 1 (process 9992): 0 0x9038e459 in read$UNIX2003 () 1 0x000be81f in mono_handle_native_sigsegv (signal=11, ctx=0xbfffd238) at ../../../../mono/mini/mini-exceptions.c:1826 2 0x0000e43e in mono_sigsegv_signal_handler (_dummy=10, info=0xbfffd1f8, context=0xbfffd238) at ../../../../mono/mini/mini.c:4846 3 4 0x028d6a63 in objc_msgSend () 5 0x01ad469f in func.24012 () 6 0x01a9f6b7 in -[MFMailComposeController _close] () 7 0x01f682f1 in -[UIActionSheet(Private) _buttonClicked:] () 8 0x01be1a6e in -[UIApplication sendAction:to:from:forEvent:] () 9 0x01c701b5 in -[UIControl sendAction:to:forEvent:] () 10 0x01c72647 in -[UIControl(Internal) _sendActionsForEvents:withEvent:] () 11 0x01c711f4 in -[UIControl touchesEnded:withEvent:] () 12 0x01c060d1 in -[UIWindow _sendTouchesForEvent:] () 13 0x01be737a in -[UIApplication sendEvent:] () 14 0x01bec732 in _UIApplicationHandleEvent () 15 0x03eb7a36 in PurpleEventCallback () 16 0x00df9064 in CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION () 17 0x00d596f7 in __CFRunLoopDoSource1 () 18 0x00d56983 in __CFRunLoopRun () 19 0x00d56240 in CFRunLoopRunSpecific () 20 0x00d56161 in CFRunLoopRunInMode () 21 0x03eb6268 in GSEventRunModal () 22 0x03eb632d in GSEventRun () 23 0x01bf042e in UIApplicationMain () 24 0x0a1e4bd9 in ?? () 25 0x0a1e4b12 in ?? () 26 0x0a1e4515 in ?? () 27 0x0a1e4451 in ?? () 28 0x0a1e44ac in ?? () 29 0x0000e202 in mono_jit_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/mini/mini.c:4733 30 0x001c92af in mono_runtime_invoke (method=0xa806e6c, obj=0x0, params=0xbfffedbc, exc=0x0) at ../../../../mono/metadata/object.c:2615 31 0x001caf6b in mono_runtime_exec_main (method=0xa806e6c, args=0xa6a34e0, exc=0x0) at ../../../../mono/metadata/object.c:3581 32 0x001ca891 in mono_runtime_run_main (method=0xa806e6c, argc=0, argv=0xbfffeef4, exc=0x0) at ../../../../mono/metadata/object.c:3355 33 0x00094fe8 in mono_jit_exec (domain=0x6f8fe58, assembly=0xa200730, argc=1, argv=0xbfffeef0) at ../../../../mono/mini/driver.c:1094 34 0x0027cf05 in main () ================================================================= Got a SIGSEGV while executing native code. This usually indicates a fatal error in the mono runtime or one of the native libraries used by your application. Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr) at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26 at MonoTouch.UIKit.UIApplication.Main (System.String[] args) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31 at MailDialog.Application.Main (System.String[] args) [0x00000] in /Users/rrkhan/Projects/Sandbox/MailDialog/Main.cs:15 I have a very simple sample project illustrating the problem. I can sent you if required.

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• Help with Collision Resolution?

  - by Milo

  I'm trying to learn about physics by trying to make a simplified GTA 2 clone. My only problem is collision resolution. Everything else works great. I have a rigid body class and from there cars and a wheel class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private OBB2D predictionRect = new OBB2D(new Vector2D(), 1.0f, 1.0f, 0.0f); private float mass; private Vector2D deltaVec = new Vector2D(); private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); predictionRect.set(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); rectChanged(); } public void setPredictionLocation(Vector2D position, float angle) { getPredictionRect().set(position, getWidth(), getHeight(), angle); } public void setPredictionCenter(Vector2D center) { getPredictionRect().moveTo(center); } public void setPredictionAngle(float angle) { predictionRect.setAngle(angle); } public Vector2D getPosition() { return getRect().getCenter(); } public OBB2D getPredictionRect() { return predictionRect; } @Override public void update(float timeStep) { doUpdate(false,timeStep); } public void doUpdate(boolean prediction, float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); if(prediction) { Vector2D velocity = Vector2D.add(this.velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setPredictionCenter(c); //forces = new Vector2D(0,0); //clear forces } else { velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); deltaVec.x = v.x - c.x; deltaVec.y = v.y - c.y; deltaVec.normalize(); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; } //angular float angAcc = torque / inertia; if(prediction) { float angularVelocity = this.angularVelocity + angAcc * timeStep; setPredictionAngle(getAngle() + angularVelocity * timeStep); //torque = 0; //clear torque } else { angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } } public void updatePrediction(float timeStep) { doUpdate(true, timeStep); } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } public Vector2D getDeltaVec() { return deltaVec; } } Vehicle public class Wheel { private Vector2D forwardVec; private Vector2D sideVec; private float wheelTorque; private float wheelSpeed; private float wheelInertia; private float wheelRadius; private Vector2D position = new Vector2D(); public Wheel(Vector2D position, float radius) { this.position = position; setSteeringAngle(0); wheelSpeed = 0; wheelRadius = radius; wheelInertia = (radius * radius) * 1.1f; } public void setSteeringAngle(float newAngle) { Matrix mat = new Matrix(); float []vecArray = new float[4]; //forward Vector vecArray[0] = 0; vecArray[1] = 1; //side Vector vecArray[2] = -1; vecArray[3] = 0; mat.postRotate(newAngle / (float)Math.PI * 180.0f); mat.mapVectors(vecArray); forwardVec = new Vector2D(vecArray[0], vecArray[1]); sideVec = new Vector2D(vecArray[2], vecArray[3]); } public void addTransmissionTorque(float newValue) { wheelTorque += newValue; } public float getWheelSpeed() { return wheelSpeed; } public Vector2D getAnchorPoint() { return position; } public Vector2D calculateForce(Vector2D relativeGroundSpeed, float timeStep, boolean prediction) { //calculate speed of tire patch at ground Vector2D patchSpeed = Vector2D.scalarMultiply(Vector2D.scalarMultiply( Vector2D.negative(forwardVec), wheelSpeed), wheelRadius); //get velocity difference between ground and patch Vector2D velDifference = Vector2D.add(relativeGroundSpeed , patchSpeed); //project ground speed onto side axis Float forwardMag = new Float(0.0f); Vector2D sideVel = velDifference.project(sideVec); Vector2D forwardVel = velDifference.project(forwardVec, forwardMag); //calculate super fake friction forces //calculate response force Vector2D responseForce = Vector2D.scalarMultiply(Vector2D.negative(sideVel), 2.0f); responseForce = Vector2D.subtract(responseForce, forwardVel); float topSpeed = 500.0f; //calculate torque on wheel wheelTorque += forwardMag * wheelRadius; //integrate total torque into wheel wheelSpeed += wheelTorque / wheelInertia * timeStep; //top speed limit (kind of a hack) if(wheelSpeed > topSpeed) { wheelSpeed = topSpeed; } //clear our transmission torque accumulator wheelTorque = 0; //return force acting on body return responseForce; } public void setTransmissionTorque(float newValue) { wheelTorque = newValue; } public float getTransmissionTourque() { return wheelTorque; } public void setWheelSpeed(float speed) { wheelSpeed = speed; } } //our vehicle object public class Vehicle extends RigidBody { private Wheel [] wheels = new Wheel[4]; private boolean throttled = false; public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //front wheels wheels[0] = new Wheel(new Vector2D(halfSize.x, halfSize.y), 0.45f); wheels[1] = new Wheel(new Vector2D(-halfSize.x, halfSize.y), 0.45f); //rear wheels wheels[2] = new Wheel(new Vector2D(halfSize.x, -halfSize.y), 0.75f); wheels[3] = new Wheel(new Vector2D(-halfSize.x, -halfSize.y), 0.75f); super.initialize(halfSize, mass, bitmap); } public void setSteering(float steering) { float steeringLock = 0.13f; //apply steering angle to front wheels wheels[0].setSteeringAngle(steering * steeringLock); wheels[1].setSteeringAngle(steering * steeringLock); } public void setThrottle(float throttle, boolean allWheel) { float torque = 85.0f; throttled = true; //apply transmission torque to back wheels if (allWheel) { wheels[0].addTransmissionTorque(throttle * torque); wheels[1].addTransmissionTorque(throttle * torque); } wheels[2].addTransmissionTorque(throttle * torque); wheels[3].addTransmissionTorque(throttle * torque); } public void setBrakes(float brakes) { float brakeTorque = 15.0f; //apply brake torque opposing wheel vel for (Wheel wheel : wheels) { float wheelVel = wheel.getWheelSpeed(); wheel.addTransmissionTorque(-wheelVel * brakeTorque * brakes); } } public void doUpdate(float timeStep, boolean prediction) { for (Wheel wheel : wheels) { float wheelVel = wheel.getWheelSpeed(); //apply negative force to naturally slow down car if(!throttled && !prediction) wheel.addTransmissionTorque(-wheelVel * 0.11f); Vector2D worldWheelOffset = relativeToWorld(wheel.getAnchorPoint()); Vector2D worldGroundVel = pointVelocity(worldWheelOffset); Vector2D relativeGroundSpeed = worldToRelative(worldGroundVel); Vector2D relativeResponseForce = wheel.calculateForce(relativeGroundSpeed, timeStep,prediction); Vector2D worldResponseForce = relativeToWorld(relativeResponseForce); applyForce(worldResponseForce, worldWheelOffset); } //no throttling yet this frame throttled = false; if(prediction) { super.updatePrediction(timeStep); } else { super.update(timeStep); } } @Override public void update(float timeStep) { doUpdate(timeStep,false); } public void updatePrediction(float timeStep) { doUpdate(timeStep,true); } public void inverseThrottle() { float scalar = 0.2f; for(Wheel wheel : wheels) { wheel.setTransmissionTorque(-wheel.getTransmissionTourque() * scalar); wheel.setWheelSpeed(-wheel.getWheelSpeed() * 0.1f); } } } And my big hack collision resolution: private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_STEAL_CAR)) { vehicle.setThrottle(-1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); //vehicle.update(16.6666666f / 1000.0f); boolean colided = false; vehicle.updatePrediction(16.66666f / 1000.0f); List<Entity> buildings = world.queryStaticSolid(vehicle,vehicle.getPredictionRect()); if(buildings.size() > 0) { colided = true; } if(!colided) { vehicle.update(16.66f / 1000.0f); } else { Vector2D delta = vehicle.getDeltaVec(); vehicle.setVelocity(Vector2D.negative(vehicle.getVelocity().multiply(0.2f)). add(delta.multiply(-1.0f))); vehicle.inverseThrottle(); } } Here is OBB public class OBB2D { // Corners of the box, where 0 is the lower left. private Vector2D corner[] = new Vector2D[4]; private Vector2D center = new Vector2D(); private Vector2D extents = new Vector2D(); private RectF boundingRect = new RectF(); private float angle; //Two edges of the box extended away from corner[0]. private Vector2D axis[] = new Vector2D[2]; private double origin[] = new double[2]; public OBB2D(Vector2D center, float w, float h, float angle) { set(center,w,h,angle); } public OBB2D(float left, float top, float width, float height) { set(new Vector2D(left + (width / 2), top + (height / 2)),width,height,0.0f); } public void set(Vector2D center,float w, float h,float angle) { Vector2D X = new Vector2D( (float)Math.cos(angle), (float)Math.sin(angle)); Vector2D Y = new Vector2D((float)-Math.sin(angle), (float)Math.cos(angle)); X = X.multiply( w / 2); Y = Y.multiply( h / 2); corner[0] = center.subtract(X).subtract(Y); corner[1] = center.add(X).subtract(Y); corner[2] = center.add(X).add(Y); corner[3] = center.subtract(X).add(Y); computeAxes(); extents.x = w / 2; extents.y = h / 2; computeDimensions(center,angle); } private void computeDimensions(Vector2D center,float angle) { this.center.x = center.x; this.center.y = center.y; this.angle = angle; boundingRect.left = Math.min(Math.min(corner[0].x, corner[3].x), Math.min(corner[1].x, corner[2].x)); boundingRect.top = Math.min(Math.min(corner[0].y, corner[1].y),Math.min(corner[2].y, corner[3].y)); boundingRect.right = Math.max(Math.max(corner[1].x, corner[2].x), Math.max(corner[0].x, corner[3].x)); boundingRect.bottom = Math.max(Math.max(corner[2].y, corner[3].y),Math.max(corner[0].y, corner[1].y)); } public void set(RectF rect) { set(new Vector2D(rect.centerX(),rect.centerY()),rect.width(),rect.height(),0.0f); } // Returns true if other overlaps one dimension of this. private boolean overlaps1Way(OBB2D other) { for (int a = 0; a < axis.length; ++a) { double t = other.corner[0].dot(axis[a]); // Find the extent of box 2 on axis a double tMin = t; double tMax = t; for (int c = 1; c < corner.length; ++c) { t = other.corner[c].dot(axis[a]); if (t < tMin) { tMin = t; } else if (t > tMax) { tMax = t; } } // We have to subtract off the origin // See if [tMin, tMax] intersects [0, 1] if ((tMin > 1 + origin[a]) || (tMax < origin[a])) { // There was no intersection along this dimension; // the boxes cannot possibly overlap. return false; } } // There was no dimension along which there is no intersection. // Therefore the boxes overlap. return true; } //Updates the axes after the corners move. Assumes the //corners actually form a rectangle. private void computeAxes() { axis[0] = corner[1].subtract(corner[0]); axis[1] = corner[3].subtract(corner[0]); // Make the length of each axis 1/edge length so we know any // dot product must be less than 1 to fall within the edge. for (int a = 0; a < axis.length; ++a) { axis[a] = axis[a].divide((axis[a].length() * axis[a].length())); origin[a] = corner[0].dot(axis[a]); } } public void moveTo(Vector2D center) { Vector2D centroid = (corner[0].add(corner[1]).add(corner[2]).add(corner[3])).divide(4.0f); Vector2D translation = center.subtract(centroid); for (int c = 0; c < 4; ++c) { corner[c] = corner[c].add(translation); } computeAxes(); computeDimensions(center,angle); } // Returns true if the intersection of the boxes is non-empty. public boolean overlaps(OBB2D other) { if(right() < other.left()) { return false; } if(bottom() < other.top()) { return false; } if(left() > other.right()) { return false; } if(top() > other.bottom()) { return false; } if(other.getAngle() == 0.0f && getAngle() == 0.0f) { return true; } return overlaps1Way(other) && other.overlaps1Way(this); } public Vector2D getCenter() { return center; } public float getWidth() { return extents.x * 2; } public float getHeight() { return extents.y * 2; } public void setAngle(float angle) { set(center,getWidth(),getHeight(),angle); } public float getAngle() { return angle; } public void setSize(float w,float h) { set(center,w,h,angle); } public float left() { return boundingRect.left; } public float right() { return boundingRect.right; } public float bottom() { return boundingRect.bottom; } public float top() { return boundingRect.top; } public RectF getBoundingRect() { return boundingRect; } public boolean overlaps(float left, float top, float right, float bottom) { if(right() < left) { return false; } if(bottom() < top) { return false; } if(left() > right) { return false; } if(top() > bottom) { return false; } return true; } }; What I do is when I predict a hit on the car, I force it back. It does not work that well and seems like a bad idea. What could I do to have more proper collision resolution. Such that if I hit a wall I will never get stuck in it and if I hit the side of a wall I can steer my way out of it. Thanks I found this nice ppt. It talks about pulling objects apart and calculating new velocities. How could I calc new velocities in my case? http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC8QFjAB&url=http%3A%2F%2Fcoitweb.uncc.edu%2F~tbarnes2%2FGameDesignFall05%2FSlides%2FCh4.2-CollDet.ppt&ei=x4ucULy5M6-N0QGRy4D4Cg&usg=AFQjCNG7FVDXWRdLv8_-T5qnFyYld53cTQ&cad=rja

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• Resources to learn XNA for a professional c# developer

  - by Team-JoKi

  I'm a .net consultant (mainly c#) for my job, but for a while now, I've been interested in making a game in XNA (as a hobby project). I've had a "beginner" course in XNA when I was still a student, but I've lost most of the information (plus, it was VERY beginner, not enough to get you really started). So my question, which resources would be useful for me to learn XNA (books, blogs, websites, tutorials, resource websites - like textures, audio files, etc..)? I know this is a very open question, but I'm thankful for any information.

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• Best way to Draw a cube for 3D Picking

  - by Kenneth Bray

  Currently I am drawing a cube for a game that I am making and the cube draw method is below. My question is, what is the best way to draw a cube and to be able to easily find the face that the cursor is over? My draw method works just fine, but I am getting ready to start to add picking (this will be used to mold the cubes into other shaps), and would like to know the best way to find a face of the cube. public void Draw() { // center point posX, posY, posZ float radius = size / 2; //top glPushMatrix(); glBegin(GL_QUADS); { glColor3f(1.0f,0.0f,0.0f); // red glVertex3f(posX + radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY + radius, posZ + radius); } glEnd(); glPopMatrix(); //bottom glPushMatrix(); glBegin(GL_QUADS); { glColor3f(1.0f,1.0f,0.0f); // ?? color glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY - radius, posZ - radius); } glEnd(); glPopMatrix(); //right side glPushMatrix(); glBegin(GL_QUADS); { glColor3f(1.0f,0.0f,1.0f); // ?? color glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); //left side glPushMatrix(); glBegin(GL_QUADS); { glColor3f(0.0f,1.0f,1.0f); // ?? color glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); } glEnd(); glPopMatrix(); //front side glPushMatrix(); glBegin(GL_QUADS); { glColor3f(0.0f,0.0f,1.0f); // blue glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); } glEnd(); glPopMatrix(); //back side glPushMatrix(); glBegin(GL_QUADS); { glColor3f(0.0f,1.0f,0.0f); // green glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); }

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• Xaudio2 XAPO Effects

  - by Jason Champion

  I've been working with XAudio2. After looking at the samples, example code, and sparse documentation available from Microsoft and the MSDN, I've found that there aren't any easy-to-find resources on creating and using XAPO effects, nor any XAPO effects produced by third parties that I can download and/or buy. What it looks like is that if I create an app that uses XAPO effects, I'll have to create them all myself because there's no community of existing applications like there is with technologies like Apple's AU or Steinberg's VST. Is this true, or are there others using XAudio2 and XAPO and I just haven't found them? Is there a place to ask programmer-support-related questions about XAudio2 and related technologies (or is this the best destination)? The best I've found so far are the XNA forums, which are game-specific and sparsely populated in the audio area.

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• set TouchEvent to every particle in SpriteParticleSystem in andEngine livewallpaper

  - by Girish Bhutiya

  All I have working on andEngine Live wallpaper and I have use SpriteParticleSystem. I want to add touch event to every Sprite of SpriteParticleSystem and remove that sprite from scene. I have use below code for create particle system. final SpriteParticleSystem particleSystem = new SpriteParticleSystem(new PointParticleEmitter(mParticleX, mParticleY),mParticleMinRate, mParticleMaxRate, mParticleMax,this.mFlowerTextureRegion, this.getVertexBufferObjectManager()); //particleSystem.addParticleInitializer(new BlendFunctionParticleInitializer<Sprite>(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE)); particleSystem.addParticleInitializer(new VelocityParticleInitializer<Sprite>(-90, 0, 0, 0)); particleSystem.addParticleInitializer(new AccelerationParticleInitializer<Sprite>(8, -11)); particleSystem.addParticleInitializer(new RotationParticleInitializer<Sprite>(0.0f, 360.0f)); //particleSystem.addParticleInitializer(new ColorParticleInitializer<Sprite>(1.0f, 1.0f, 0.0f)); particleSystem.addParticleInitializer(new ExpireParticleInitializer<Sprite>(15.5f)); particleSystem.addParticleModifier(new ScaleParticleModifier<Sprite>(0, 5, 0.5f, 2.0f)); background = new Sprite(0, 0, backgroundTextureRegion, mEngine.getVertexBufferObjectManager()); background.setPosition((CAMERA_WIDTH - background.getWidth()) * 0.5f, (CAMERA_HEIGHT - background.getHeight()) * 0.5f); //background.setScale(1.5f); //SpriteBackground bg = new SpriteBackground(background); //mScene.setBackground(bg); this.mScene.attachChild(background); this.mScene.attachChild(particleSystem); <br> Thanks in advance.

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• How to gain accurate results with Painter's algorithm?

  - by pimvdb

  A while ago I asked how to determine when a face is overlapping another. The advice was to use a Z-buffer. However, I cannot use a Z-buffer in my current project and hence I would like to use the Painter's algorithm. I have no good clue as to when a surface is behind or in front of another, though. I've tried numerous methods but they all fail in edge cases, or they fail even in general cases. This is a list of sorting methods I've tried so far: Distance to midpoint of each face Average distance to each vertex of each face Average z value of each vertex Higest z value of vertices of each face and draw those first Lowest z value of vertices of each face and draw those last The problem is that a face might have a closer distance but is still further away. All these methods seem unreliable. Edit: For example, in the following image the surface with the blue point as midpoint is painted over the surface with the red point as midpoint, because the blue point is closer. However, this is because the surface of the red point is larger and the midpoint is further away. The surface with the red point should be painted over the blue one, because it is closer, whilst the midpoint distance says the opposite. What exactly is used in the Painter's algorithm to determine the order in which objects should be drawn?

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• OpenGL's matrix stack vs Hand multiplying

  - by deft_code

  Which is more efficient using OpenGL's transformation stack or applying the transformations by hand. I've often heard that you should minimize the number of state transitions in your graphics pipeline. Pushing and popping translation matrices seem like a big change. However, I wonder if the graphics card might be able to more than make up for pipeline hiccup by using its parallel execution hardware to bulk multiply the vertices. My specific case. I have font rendered to a sprite sheet. The coordinates of each character or a string are calculated and added to a vertex buffer. Now I need to move that string. Would it be better to iterate through the vertex buffer and adjust each of the vertices by hand or temporarily push a new translation matrix?

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• Collision detection with curves

  - by paldepind

  I'm working on a 2D game in which I would like to do collision detection between a moving circle and some kind of static curves (maybe Bezier curves). Currently my game features only straight lines as the static geometry and I'm doing the collision detection by calculating the distance from the circle to the lines, and projecting the circle out of the line in case the distance is less than the circles radius. How can I do this kind of collision detection in a relative straightforward way? I know for instance that Box2D features collision detection with Bezier curves. I don't need a full featured collision detection mechanism, just something that can do what I've described.

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• How to find working directory which works between different computers. - C

  - by Jamie Keeling

  Hello, I am running two processes,Process A is opened by Process B using the following example: createProcessHandle = CreateProcess( TEXT("C:\\Users\Jamie\\Documents\\Application\\Debug\\ProcessA.exe"), TEXT(""), NULL, NULL, FALSE, 0, NULL, NULL, &startupinfo, &process_information ); As you can see the Process is reliant on the path given to it, the problem I have is that if I change the location of my ProcessA.exe (Such as a backup/duplicate) it's a tiresome process to keep recoding the path. I want to be able to make it run no matter where it is without having to recode the path manually. Can anybody suggest a solution to this?

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• Collision detection with multiple polygons simultaneously

  - by Craig Innes

  I've written a collision system which detects/resolves collisions between a rectangular player and a convex polygon world using the Separating Axis Theorem. This scheme works fine when the player is colliding with a single polygon, but when I try to create a level made up of combinations of these shapes, the player gets "stuck" between shapes when trying to move from one polygon to the other. The reason for this seems to be that collisions are detected after the player has been pushed through the shape by its movement or gravity. When the system resolves the collision, it resolves them in an order that doesn't make sense (for example, when the player is moving from one flat rectangle to another, gravity pushes them below the ground, but the collision with the left hand side of the second block is resolved before the collision with the top of the block, meaning the player is pushed back left before being pushed back up). Other similar posts have resolved this problem by having a strict rule on which axes to resolve first. For example, always resolve the collision on the y axis, then if the object is still colliding with things, resolve on the x axis. This solution only works in the case of a completely axis oriented box world, and doesn't solve the problem if the player is stuck moving along a series of angled shapes or sliding down a wall. Does any one have any ideas of how I could alter my collision system to prevent these situations from happening?

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• simple collision detection with box2dweb

  - by skywalker

  im beginner in box2dweb that version of box2d for javascript i wrote simple gravity system and i want to detect the collision between the box and the ground , when the falling box hit the ground execute simple function like function sucs(){alert("the box on the floor !")}; this is my code var CANVAS_WIDTH = 1024, CANVAS_HEIGHT = 700, SCALE = 30; var b2Vec2 = Box2D.Common.Math.b2Vec2 , b2BodyDef = Box2D.Dynamics.b2BodyDef , b2Body = Box2D.Dynamics.b2Body , b2FixtureDef = Box2D.Dynamics.b2FixtureDef , b2Fixture = Box2D.Dynamics.b2Fixture , b2World = Box2D.Dynamics.b2World , b2MassData = Box2D.Collision.Shapes.b2MassData , b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape , b2CircleShape = Box2D.Collision.Shapes.b2CircleShape , b2DebugDraw = Box2D.Dynamics.b2DebugDraw; var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d"); var world = new b2World(new b2Vec2(0, 8), true); var fixDef = new b2FixtureDef(); var bodyDef = new b2BodyDef(); fixDef.density = 1.0; fixDef.friction = 0.5; bodyDef.type = b2Body.b2_staticBody; fixDef.shape = new b2PolygonShape; fixDef.shape.SetAsBox(20, 2); bodyDef.position.Set(10, 400 / 30 + 1.8); world.CreateBody(bodyDef).CreateFixture(fixDef); fixDef.density = 1.0; fixDef.friction = 0.5; fixDef.restitution = 0.3; bodyDef.type = b2Body.b2_dynamicBody; bodyDef.position.Set(50 / SCALE, 0 / SCALE); //bodyDef.linearVelocity.Set((Math.random() * 12) + 2, (Math.random() * 12) + 2); fixDef.shape = new b2PolygonShape(); fixDef.shape.SetAsBox(25 / SCALE, 25 / SCALE); world.CreateBody(bodyDef).CreateFixture(fixDef); var debugDraw = new b2DebugDraw(); debugDraw.SetSprite(document.getElementById("canvas").getContext("2d")); debugDraw.SetDrawScale(30.0); debugDraw.SetFillAlpha(0.5); debugDraw.SetLineThickness(1.0); debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit); world.SetDebugDraw(debugDraw); var image = new Image(); image.src = "image.png"; window.setInterval(gameLoop, 1000 / 60); function gameLoop() { world.Step(1 / 60, 8, 3); world.ClearForces(); context.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT); b = world.GetBodyList() var pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); b = b.GetNext(); pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); //b.GetAngle()++; context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); world.DrawDebugData(); };

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• gl_PointCoord always zero

  - by Jonathan

  I am trying to draw point sprites in OpenGL with a shader but gl_PointCoord is always zero. Here is my code Setup: //Shader creation..(includes glBindAttribLocation(program, ATTRIB_P, "p");) glEnableVertexAttribArray(ATTRIB_P); In the rendering loop: glUseProgram(shader_particles); float vertices[]={0.0f,0.0f,0.0f}; glEnable(GL_TEXTURE_2D); glEnable(GL_POINT_SPRITE); glEnable(GL_VERTEX_PROGRAM_POINT_SIZE); //glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);(tried with this on/off, doesn't work) glVertexAttribPointer(ATTRIB_P, 3, GL_FLOAT, GL_FALSE, 0, vertices); glDrawArrays(GL_POINTS, 0, 1); Vertex Shader: attribute highp vec4 p; void main() { gl_PointSize = 40.0f; gl_Position = p; } Fragment Shader: void main() { gl_FragColor = vec4(gl_PointCoord.st, 0, 1);//if the coords range from 0-1, this should draw a square with black,red,green,yellow corners } But this only draws a black square with a size of 40. What am I doing wrong? Edit: Point sprites work when i use the fixed function, but I need to use shaders because in the end the code will be for opengl es 2.0 glUseProgram(0); glEnable(GL_TEXTURE_2D); glEnable(GL_POINT_SPRITE); glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE); glPointSize(40); glBegin(GL_POINTS); glVertex3f(0.0f,0.0f,0.0f); glEnd(); Is anyone able to get point sprites working with shader? If so, please share some code.

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• Passing multiple Vertex Attributes in GLSL 130

  - by Roy T.

  (note this question is closely related to this one however I didn't fully understand the accepted answer) To support videocards in laptops I have to rewrite my GLSL 330 shaders to GLSL 130. I'm trying to do this but somehow I don't get vertex attributes to work properly. My 330 shaders look like this: #version 330 layout(location = 0) in vec4 position; layout(location = 3) in vec4 color; smooth out vec4 theColor; void main() { gl_Position = position; theColor = color; } Now this explicit layout is not allowed in GLSL 130 so I referenced this page to see what the default layouts for some values would be. As you can see position should be the 0th vertex attribute and color should be the 3rd vertex attribute. Because this is a test case I had already configured my explicit layouts in the same way, which worked, so I now simply rewrote my shader to this and expected it to work: #version 130 smooth out vec4 theColor; void main() { gl_Position = gl_Vertex; theColor = gl_Color; } However this doesn't work, the value of gl_Color is always (1,1,1,1). So how should I pass multiple vertex attributes to my GLSL 130 shaders? For reference, this is how I set my vertex buffer object and attributes (I've just adapted this tutorial to JAVA+JOGL) gl.glBindBuffer(GL3.GL_ARRAY_BUFFER, vertex_buffer_id); gl.glEnableVertexAttribArray(0); gl.glEnableVertexAttribArray(3); gl.glVertexAttribPointer(0, 4 , GL3.GL_FLOAT, false, 0, 0); gl.glVertexAttribPointer(3, 4, GL3.GL_FLOAT, false, 0, 4*4*4); gl.glDrawArrays(GL3.GL_TRIANGLE_STRIP, 0, 4); gl.glDisableVertexAttribArray(0); gl.glDisableVertexAttribArray(3); EDIT I solved the problem by querying for the layout locations of position an color using glGetAttribLocation however I still don't understand why the 'hardcoded' values like gl_Color didn't work, can't I upload data in there as normal? Shouldn't they be used?

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• Get vertex colors from fbx (OpenGL, FBX SDK)

  - by instancedName

  I'm kinda stuck with this one. I managed to get vertex positions, indices, normals, but I don't quite understand how te get vertex colors. I need them to fill my buffer. I tried funcion mesh-GetElementVertexColorCount() and then to iterate trough all of them, but it returns zero. I alse tried to get layer, and then use layer-GetVertexColors(), but it returns NULL pointer. Can anyone help me with this one?

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• Keep basic game physics separate from basic game object? [on hold]

  - by metamorphosis

  If anybody has dealt with a similar situation I'd be interested in your experience/wisdom, I'm developing a 2D game library in C++, I have game objects which have very basic physics, they also have movement classes attached to differing states, for example, a different movement type based on whether the character is jumping, on ice, whatever. In terms of storing velocity and acceleration impulses, are they best held by the object? Or by the associated movement class? The reason I ask is that I can see advantages to both approaches- if you store physics data in the movement class, you have to pass physics information between class instances when a state change occurs (ie. impulses, gravity etc) but the class has total control over whether those physics are updated or not. An obvious example of how this would be useful was if an object was affected by something which caused it to ignore gravity, or something like that. on the other hand if you store the physics data in the object class, it feels more logical, you don't have to go around passing physics impulses and gravity etc, however the control that the movement class has over the object's physics becomes more convoluted. Basically the difference is between: object->physics stacks (acceleration impulses etc) ->physics functions ->movement type <-movement type makes physics function calls through object and object->movement type->physics stacks ->physics functions ->object forwards external physics calls onto movement type ->object transfers physics stacks between movement types when state change occurs Are there best practices here?

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• How to use caching to increase render performance?

  - by Christian Ivicevic

  First of all I am going to cover the basic design of my 2d tile-based engine written with SDL in C++, then I will point out what I am up to and where I need some hints. Concept of my engine My engine uses the concept of GameScreens which are stored on a stack in the main game class. The main methods of a screen are usually LoadContent, Render, Update and InitMultithreading. (I use the last one because I am using v8 as a JavaScript bridge to the engine. The main game loop then renders the top screen on the stack (if there is one; otherwise, it exits the game) - actually it calls the render methods, but stores all items to be rendered in a list. After gathering all this information the methods like SDL_BlitSurface are called by my GameUIRenderer which draws the enqueued content and then draws some overlay. The code looks like this: while(Game is running) { Handle input if(Screens on stack == 0) exit Update timer etc. Clear the screen Peek the screen on the stack and collect information on what to render Actually render the enqueue screen stuff and some overlay etc. Flip the screen } The GameUIRenderer uses as hinted a std::vector<std::shared_ptr<ImageToRender>> to hold all necessary information described by this class: class ImageToRender { private: SDL_Surface* image; int x, y, w, h, xOffset, yOffset; }; This bunch of attributes is usually needed if I have a texture atlas with all tiles in one SDL_Surface and then the engine should crop one specific area and draw this to the screen. The GameUIRenderer::Render() method then just iterates over all elements and renders them something like this: std::for_each( this->m_vImageVector.begin(), this->m_vImageVector.end(), [this](std::shared_ptr<ImageToRender> pCurrentImage) { SDL_Rect rc = { pCurrentImage->x, pCurrentImage->y, 0, 0 }; // For the sake of simplicity ignore offsets... SDL_Rect srcRect = { 0, 0, pCurrentImage->w, pCurrentImage->h }; SDL_BlitSurface(pCurrentImage->pImage, &srcRect, g_pFramework->GetScreen(), &rc); } ); this->m_vImageVector.clear(); Current ideas which need to be reviewed The specified approach works really good and IMHO it is really has a good structure, however the performance could be definitely increased. I would like to know what do you suggest, how to implement efficient caching of surfaces etc so that there is no need to redraw the same scene over and over again? The map itself would be almost static, only when the player moves, we would need to move the map. Furthermore animated entities would either require updates of the whole map or updates of only the specific areas the entities are currently moving in. My first approaches were to include a flag IsTainted which should be used by the GameUIRenderer to decide whether to redraw everything or use cached version (or to not render anything so that we do not have to Clear the screen and let the last frame persist). However this seems to be quite messy if I have to manually handle in my Render method of the screen class if something has changed or not.

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• Should I refer to browser-based games as HTML5 games or Javascript games?

  - by Bane

  First of all, I know that there are alternatives to both HTML5 and Javascript, but I worded the question so generally ("browser-based") because if I had said "HTML5" or "Javascript" games that would already imply an answer to the question. When writing wiki posts or discussing, I usually call these games "HTML5/Javascript" games. They are written in Javascript, using the new HTML5 technology. What is the proper way to call them: HTML5 or Javascript games? I see that most people opt for HTML5, why?

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• Rain effect using DirectX 9 capabilities

  - by teodron

  Is it possible to achieve something similar to nVidia's rain demo using only shader model 3.0 capabilities? If yes, could you point out a few documents/web resources that are suitable candidates and do not require a heavy programming load (e.g. not more than two hard weeks of programming for one single person)? It would be nice if the answer could also contain a pro/con phrase for the proposed idea (e.g. postprocessing rain shader vs. a particle based effect).

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• How do I draw a border around a display object in Corona Lua?

  - by Greg

  What would be the easiest way to draw a thin border around a display object in Corona Lua? You could assume it's rectangular image display object. EDIT - re "this question shows no research effort. You should tell us what you've tried and how it didn't work" Reviewed API and could not find a "border" method/property on displayObject Have tried creating a black box slightly bigger behind object, however can not see how to place object behind an existing object hence question How do I move an existing display object behind another in Corona Lua? Google results for putting a border around a display object in corona didn't help

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• Laser Beam End Points Problems

  - by user36159

  I am building a game in XNA that features colored laser beams in 3D space. The beams are defined as: Segment start position Segment end position Line width For rendering, I am using 3 quads: Start point billboard End point billboard Middle section quad whose forward vector is the slope of the line and whose normal points to the camera The problem is that using additive blending, the end points and middle section overlap, which looks quite jarring. However, I need the endpoints in case the laser is pointing towards the camera! See the blue laser in particular:

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• Cocos2d-x v3 invalid conversion from 'cocos2d::Layer* [on hold]

  - by Hammerh5

  Hello guys I'm learning cocos2d-x v3 right but most of the code that I can find is to the version 2. My specific error is this one, when I try to compile my cocos2s-x 3 project this error shows. invalid conversion from 'cocos2d::Layer to Game* [-fpermisive]* What I want to do is create a new game scene in the following code: //Game.cpp #include "Game.h" Scene* Game::scene() { scene *sc = CCScene::create(); sc->setTag(TAG_GAME_SCENE); const Game *g = Game::create(); //Here is where the conversions fails. sc->addChild(g, 0, TAG_GAME_LAYER); return sc; } Of course this is my header file //Game.h #include "cocos2d.h" #include "Mole.h" #include "AppDelegate.h" using namespace cocos2d; class Game: public cocos2d::Layer { cocos2d::CCArray *moles; float timeBetweenMoles, timeElapsed, increaseMolesAtTime, increaseElapsed, lastMoleHiTime; int molesAtOnce; cocos2d::CCSize s; bool isPaused; public: CCString *missSound, *hitSound; static cocos2d::Scene* scene(); virtual bool init(); void showMole(); void initializeGame(); void onEnterTransitionDidFinish(); void onExit(); void onTouchesBegan(const std::vector<cocos2d::Touch *> &touches, cocos2d::Event *event); void tick(float dt); cocos2d::CCArray* getMoles(bool isUp); //LAYER_CREATE_FUNC(Game); }; #endif /* GAME_H_ */ I don't know what's wrong I suppose this code works fine in Cocos2d-x v2. It's maybe some changes in the C++ version ?

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• Best solution for multiplayer realtime Android game

  - by piotrek

  I plan to make multiplayer realtime game for Android (2-8 players), and I consider, which solution for multiplayer organization is the best: Make server on PC, and client on mobile, all communition go through server ( ClientA - PC SERVER - All Clients ) Use bluetooth, I don't used yet, and I don't know is it hard to make multiplayer on bluetooth Make server on one of devices, and other devices connect ( through network, but I don't know is it hard to resolve problem with devices over NAT ? ) Other solution ?

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• 2d movement solution

  - by Phil

  Hi! I'm making a simple top-down tank game on the ipad where the user controls the movement of the tank with the left "joystick" and the rotation of the turret with the right one. I've spent several hours just trying to get it to work decently but now I turn to the pros :) I have two referencial objects, one for the movement and one for the rotation. The referencial objects always stay max two units away from the tank and I use them to tell the tank in what direction to move. I chose this approach to decouple movement and rotational behaviour from the raw input of the joysticks, I believe this will make it simpler to implement whatever behaviour I want for the tank. My problem is 1; the turret rotates the long way to the target. With this I mean that the target can be -5 degrees away in rotation and still it rotates 355 degrees instead of -5 degrees. I can't figure out why. The other problem is with the movement. It just doesn't feel right to have the tank turn while moving. I'd like to have a solution that would work as well for the AI as for the player. A blackbox function for the movement where the player only specifies in what direction it should move and it moves there under the constraints that are imposed on it. I am using the standard joystick class found in the Unity iPhone package. This is the code I'm using for the movement: public class TankFollow : MonoBehaviour { //Check angle difference and turn accordingly public GameObject followPoint; public float speed; public float turningSpeed; void Update() { transform.position = Vector3.Slerp(transform.position, followPoint.transform.position, speed * Time.deltaTime); //Calculate angle var forwardA = transform.forward; var forwardB = (followPoint.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 5) { //Rotate to transform.Rotate(new Vector3(0, (-turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 5) { transform.Rotate(new Vector3(0, (turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } transform.position = new Vector3(transform.position.x, 0, transform.position.z); } } And this is the code I'm using to rotate the turret: void LookAt() { var forwardA = -transform.right; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff - 180 > 1) { //Rotate to transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff - 180 < -1) { transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); print((angleDiff - 180).ToString()); } else { } } Since I want the turret reference point to turn in relation to the tank (when you rotate the body, the turret should follow and not stay locked on since it makes it impossible to control when you've got two thumbs to work with), I've made the TurretFollowPoint a child of the Turret object, which in turn is a child of the body. I'm thinking that I'm making it too difficult for myself with the reference points but I'm imagining that it's a good idea. Please be honest about this point. So I'll be grateful for any help I can get! I'm using Unity3d iPhone. Thanks!

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• Trying to Draw a 2D Triangle in OpenGL ES 2.0

  - by Nathan Campos

  I'm trying to convert a code from OpenGL to OpenGL ES 2.0 (for the BlackBerry PlayBook). So far what I got is this (just the part of the code that should draw the triangle): void setupScene() { glClearColor(250, 250, 250, 1); glViewport(0, 0, 600, 1024); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); } void drawScene() { setupScene(); glColorMask(0, 0, 0, 1); const GLfloat triangleVertices[] = { 100, 100, 150, 0, 200, 100 }; glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, triangleVertices); glEnableVertexAttribArray(0); glDrawArrays(GL_TRIANGLES, 0, 2); } void render() { drawScene(); bbutil_swap(); } The problem is that when I launch the app instead of showing me the triangle the screen just flickers (very fast) from white to gray. Any idea what I'm doing wrong? Also, here is the entire code if you need: Full source code

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