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  • Can't get sprite to rotate correctly?

    - by rphello101
    I'm attempting to play with graphics using Java/Slick 2d. I'm trying to get my sprite to rotate to wherever the mouse is on the screen and then move accordingly. I figured the best way to do this was to keep track of the angle the sprite is at since I have to multiply the cosine/sine of the angle by the move speed in order to get the sprite to go "forwards" even if it is, say, facing 45 degrees in quadrant 3. However, before I even worry about that, I'm having trouble even getting my sprite to rotate in the first place. Preliminary console tests showed that this code worked, but when applied to the sprite, it just kind twitches. Anyone know what's wrong? int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x; int pY = sprite.y; int tempY, tempX; double mAng, pAng = sprite.angle; double angRotate=0; if(mX!=pX){ tempY=pY-mY; tempX=mX-pX; mAng = Math.toDegrees(Math.atan2(Math.abs((tempY)),Math.abs((tempX)))); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=270; else mAng=90; } //Calculations if(mX<pX&&mY<pY){ //If in Q2 mAng = 180-mAng; } if(mX<pX&&mY>pY){ //If in Q3 mAng = 180+mAng; } if(mX>pX&&mY>pY){ //If in Q4 mAng = 360-mAng; } angRotate = mAng-pAng; sprite.angle = mAng; sprite.image.setRotation((float)angRotate);

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  • Flickering when accessing texture by offset

    - by TravisG
    I have this simple compute shader that basically just takes the input from one image and writes it to another. Both images are 128/128/128 in size and glDispatchCompute is called with (128/8,128/8,128/8). The source images are cleared to 0 before this compute shader is executed, so no undefined values should be floating around in there. (I have the appropriate memory barrier on the C++ side set before the 3D texture is accessed). This version works fine: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord)); } Reading values from pong shows that it's just a copy, as intended. However, when I load data from ping with an offset: #version 430 layout (location = 0, rgba16f) uniform image3D ping; layout (location = 1, rgba16f) uniform image3D pong; layout (local_size_x = 8, local_size_y = 8, local_size_z = 8) in; void main() { ivec3 sampleCoord = gl_GlobalInvocationID.xyz; imageStore(pong, imageLoad(ping,sampleCoord+ivec3(1,0,0))); } The data that is written to pong seems to depend on the order of execution of the threads within the work groups, which makes no sense to me. When reading from the pong texture, visible flickering occurs in some spots on the texture. What am I doing wrong here?

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  • How to proceed on the waypoint path?

    - by Alpha Carinae
    I'm using Dijkstra algorithm to find shortest path and I'm drawing this path on the screen. As the character object moves on, path updates itself(shortens as the object approaches the target and gets longer as the object moves away from it.) I tried to visualize my problem. This is the beginning state. 'A' node is the target, path is the blue and the object is the green one. I draw this path, from object to the closest node. In this case my problem occurs. Because 'D' node is more closer to the object than 'C' node, something like this happens: So, how can i decide that the object passed the 'D' node? Path should be look like this: One thing comes to my mind is that I use some distance variables between the two closest nodes in the route path. (In this example these are 'C' and 'D' nodes.) As the object approaches 'C' and moves away from the 'D' node at the same time, this means character passed the 'D'. However, I think there are some standardized and easy ways to solve this. What approach should I take?

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  • GLSL compiler messages from different vendors [on hold]

    - by revers
    I'm writing a GLSL shader editor and I want to parse GLSL compiler messages to make hyperlinks to invalid lines in a shader code. I know that these messages are vendor specific but currently I have access only to AMD's video cards. I want to handle at least NVidia's and Intel's hardware, apart from AMD's. If you have video card from different vendor than AMD, could you please give me the output of following C++ program: #include <GL/glew.h> #include <GL/freeglut.h> #include <iostream> using namespace std; #define STRINGIFY(X) #X static const char* fs = STRINGIFY( out vec4 out_Color; mat4 m; void main() { vec3 v3 = vec3(1.0); vec2 v2 = v3; out_Color = vec4(5.0 * v2.x, 1.0); vec3 k = 3.0; float = 5; } ); static const char* vs = STRINGIFY( in vec3 in_Position; void main() { vec3 v(5); gl_Position = vec4(in_Position, 1.0); } ); void printShaderInfoLog(GLint shader) { int infoLogLen = 0; int charsWritten = 0; GLchar *infoLog; glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLogLen); if (infoLogLen > 0) { infoLog = new GLchar[infoLogLen]; glGetShaderInfoLog(shader, infoLogLen, &charsWritten, infoLog); cout << "Log:\n" << infoLog << endl; delete [] infoLog; } } void printProgramInfoLog(GLint program) { int infoLogLen = 0; int charsWritten = 0; GLchar *infoLog; glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLogLen); if (infoLogLen > 0) { infoLog = new GLchar[infoLogLen]; glGetProgramInfoLog(program, infoLogLen, &charsWritten, infoLog); cout << "Program log:\n" << infoLog << endl; delete [] infoLog; } } void initShaders() { GLuint v = glCreateShader(GL_VERTEX_SHADER); GLuint f = glCreateShader(GL_FRAGMENT_SHADER); GLint vlen = strlen(vs); GLint flen = strlen(fs); glShaderSource(v, 1, &vs, &vlen); glShaderSource(f, 1, &fs, &flen); GLint compiled; glCompileShader(v); bool succ = true; glGetShaderiv(v, GL_COMPILE_STATUS, &compiled); if (!compiled) { cout << "Vertex shader not compiled." << endl; succ = false; } printShaderInfoLog(v); glCompileShader(f); glGetShaderiv(f, GL_COMPILE_STATUS, &compiled); if (!compiled) { cout << "Fragment shader not compiled." << endl; succ = false; } printShaderInfoLog(f); GLuint p = glCreateProgram(); glAttachShader(p, v); glAttachShader(p, f); glLinkProgram(p); glUseProgram(p); printProgramInfoLog(p); if (!succ) { exit(-1); } delete [] vs; delete [] fs; } int main(int argc, char* argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA); glutInitWindowSize(600, 600); glutCreateWindow("Triangle Test"); glewInit(); GLenum err = glewInit(); if (GLEW_OK != err) { cout << "glewInit failed, aborting." << endl; exit(1); } cout << "Using GLEW " << glewGetString(GLEW_VERSION) << endl; const GLubyte* renderer = glGetString(GL_RENDERER); const GLubyte* vendor = glGetString(GL_VENDOR); const GLubyte* version = glGetString(GL_VERSION); const GLubyte* glslVersion = glGetString(GL_SHADING_LANGUAGE_VERSION); GLint major, minor; glGetIntegerv(GL_MAJOR_VERSION, &major); glGetIntegerv(GL_MINOR_VERSION, &minor); cout << "GL Vendor : " << vendor << endl; cout << "GL Renderer : " << renderer << endl; cout << "GL Version : " << version << endl; cout << "GL Version : " << major << "." << minor << endl; cout << "GLSL Version : " << glslVersion << endl; initShaders(); return 0; } On my video card it gives: Status: Using GLEW 1.7.0 GL Vendor : ATI Technologies Inc. GL Renderer : ATI Radeon HD 4250 GL Version : 3.3.11631 Compatibility Profile Context GL Version : 3.3 GLSL Version : 3.30 Vertex shader not compiled. Log: Vertex shader failed to compile with the following errors: ERROR: 0:1: error(#132) Syntax error: '5' parse error ERROR: error(#273) 1 compilation errors. No code generated Fragment shader not compiled. Log: Fragment shader failed to compile with the following errors: WARNING: 0:1: warning(#402) Implicit truncation of vector from size 3 to size 2. ERROR: 0:1: error(#174) Not enough data provided for construction constructor WARNING: 0:1: warning(#402) Implicit truncation of vector from size 1 to size 3. ERROR: 0:1: error(#132) Syntax error: '=' parse error ERROR: error(#273) 2 compilation errors. No code generated Program log: Vertex and Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed. Or if you like, you could give me other compiler messages than proposed by me. To summarize, the question is: What are GLSL compiler messages formats (INFOs, WARNINGs, ERRORs) for different vendors? Please give me examples or pattern explanation. EDIT: Ok, it seems that this question is too broad, then shortly: How does NVidia's and Intel's GLSL compilers present ERROR and WARNING messages? AMD/ATI uses patterns like this: ERROR: <position>:<line_number>: <message> WARNING: <position>:<line_number>: <message> (examples are above).

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  • Continuous Movement of gun bullet

    - by Siddharth
    I was using box2d for the movement of the body. When I apply gravity (0,0) the bullet continuously move but when I change gravity to the earth the behavior was changed. I also try to apply continuous force to the bullet body but the behavior was not so good. So please provide any suggestion to continuously move bullet body in earth gravity. currentVelocity = bulletBody.getLinearVelocity(); if (currentVelocity.len() < speed|| currentVelocity.len() > speed + 0.25f) { velocityChange = Math.abs(speed - currentVelocity.len()); currentVelocity.set(currentVelocity.x* velocityChange, currentVelocity.y*velocityChange); bulletBody.applyLinearImpulse(currentVelocity,bulletBody.getWorldCenter()); } I apply above code for the continuous velocity of the body. And also I did not able to find any setGravityScale method in the library.

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  • strange behavior in Box2D+LibGDX when applying impulse

    - by Z0lenDer
    I have been playing around with Box2D and LibGDX and have been using a sample code from DecisionTreeGames as the testing ground. Now I have a screen with four walls and a rectangle shape, lets call it a brick. When I use applyLinearImpulse to the brick, it starts bouncing right and left without any pattern and won't stop! I tried adding friction and increasing the density, but the behavior still remains the same. Here are some of the code that might be useful: method for applying the impulse: center = brick.getWorldCenter(); brick.applyLinearImpulse(20, 0, center.x, center.y); Defining the brick: brick_bodyDef.type = BodyType.DynamicBody; brick_bodyDef.position.set(pos); // brick is initially on the ground brick_bodyDef.angle = 0; brick_body = world.createBody(brick_bodyDef); brick_body.setBullet(true); brick_bodyShape.setAsBox(w,h); brick_fixtureDef.density = 0.9f; brick_fixtureDef.restitution = 1; brick_fixtureDef.shape = brick_bodyShape; brick_fixtureDef.friction=1; brick_body.createFixture(fixtureDef); Walls are defined the same only their bullet value is set to false I would really appreciate it if you could help me have a change this code to have a realistic behavior (i.e. when I apply impulse to the brick it should trip a few times and then stop completely).

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  • Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

    - by stoney78us
    I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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  • How to translate along Z axis in OpenTK

    - by JeremyJAlpha
    I am playing around with an OpenGL sample application I downloaded for Xamarin-Android. The sample application produces a rotating colored cube I would simply like to edit it so that the rotating cube is translated along the Z axis and disappears into the distance. I modified the code by: adding an cumulative variable to store my Z distance, adding GL.Enable(All.DepthBufferBit) - unsure if I put it in the right place, adding GL.Translate(0.0f, 0.0f, Depth) - before the rotate functions, Result: cube rotates a couple of times then disappears, it seems to be getting clipped out of the frustum. So my question is what is the correct way to use and initialize the Z buffer and get the cube to travel along the Z axis? I am sure I am missing some function calls but am unsure of what they are and where to put them. I apologise in advance as this is very basic stuff but am still learning :P, I would appreciate it if anyone could show me the best way to get the cube to still rotate but to also move along the Z axis. I have commented all my modifications in the code: // This gets called when the drawing surface is ready protected override void OnLoad (EventArgs e) { // this call is optional, and meant to raise delegates // in case any are registered base.OnLoad (e); // UpdateFrame and RenderFrame are called // by the render loop. This is takes effect // when we use 'Run ()', like below UpdateFrame += delegate (object sender, FrameEventArgs args) { // Rotate at a constant speed for (int i = 0; i < 3; i ++) rot [i] += (float) (rateOfRotationPS [i] * args.Time); }; RenderFrame += delegate { RenderCube (); }; GL.Enable(All.DepthBufferBit); //Added by Noob GL.Enable(All.CullFace); GL.ShadeModel(All.Smooth); GL.Hint(All.PerspectiveCorrectionHint, All.Nicest); // Run the render loop Run (30); } void RenderCube () { GL.Viewport(0, 0, viewportWidth, viewportHeight); GL.MatrixMode (All.Projection); GL.LoadIdentity (); if ( viewportWidth > viewportHeight ) { GL.Ortho(-1.5f, 1.5f, 1.0f, -1.0f, -1.0f, 1.0f); } else { GL.Ortho(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f); } GL.MatrixMode (All.Modelview); GL.LoadIdentity (); Depth -= 0.02f; //Added by Noob GL.Translate(0.0f,0.0f,Depth); //Added by Noob GL.Rotate (rot[0], 1.0f, 0.0f, 0.0f); GL.Rotate (rot[1], 0.0f, 1.0f, 0.0f); GL.Rotate (rot[2], 0.0f, 1.0f, 0.0f); GL.ClearColor (0, 0, 0, 1.0f); GL.Clear (ClearBufferMask.ColorBufferBit); GL.VertexPointer(3, All.Float, 0, cube); GL.EnableClientState (All.VertexArray); GL.ColorPointer (4, All.Float, 0, cubeColors); GL.EnableClientState (All.ColorArray); GL.DrawElements(All.Triangles, 36, All.UnsignedByte, triangles); SwapBuffers (); }

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  • Split vector vs matrix notation for transformation

    - by seahorse
    Some rendering engines like Ogre prefer to use a individual vector based notation for transformations like the following Split vector notation: Net Transformation is represented by Scale vector = sx, sy, sz Transformation vector = tx, ty, tz Rotation Quaternion Vector = w,x,y,z Matrix notation: There are other engines which simply use a net combined transformation matrix. What are the advantages of the first notation over the second? Also for animation interpolation does it work in the first notation that we interpolate across the individual components and use the interpolated parts to get the net transformation? Is this another advantage?

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  • Moving player in direciton camera is facing

    - by Samurai Fox
    I have a 3rd person camera which can rotate around the player. My problem is that wherever camera is facing, players forward is always the same direction. For example when camera is facing the right side of the player, when I press button to move forward, I want player to turn to the left and make that the "new forward". My camera script so far: using UnityEngine; using System.Collections; public class PlayerScript : MonoBehaviour { public float RotateSpeed = 150, MoveSpeed = 50; float DeltaTime; void Update() { DeltaTime = Time.deltaTime; transform.Rotate(0, Input.GetAxis("LeftX") * RotateSpeed * DeltaTime, 0); transform.Translate(0, 0, -Input.GetAxis("LeftY") * MoveSpeed * DeltaTime); } } public class CameraScript : MonoBehaviour { public GameObject Target; public float RotateSpeed = 170, FollowDistance = 20, FollowHeight = 10; float RotateSpeedPerTime, DesiredRotationAngle, DesiredHeight, CurrentRotationAngle, CurrentHeight, Yaw, Pitch; Quaternion CurrentRotation; void LateUpdate() { RotateSpeedPerTime = RotateSpeed * Time.deltaTime; DesiredRotationAngle = Target.transform.eulerAngles.y; DesiredHeight = Target.transform.position.y + FollowHeight; CurrentRotationAngle = transform.eulerAngles.y; CurrentHeight = transform.position.y; CurrentRotationAngle = Mathf.LerpAngle(CurrentRotationAngle, DesiredRotationAngle, 0); CurrentHeight = Mathf.Lerp(CurrentHeight, DesiredHeight, 0); CurrentRotation = Quaternion.Euler(0, CurrentRotationAngle, 0); transform.position = Target.transform.position; transform.position -= CurrentRotation * Vector3.forward * FollowDistance; transform.position = new Vector3(transform.position.x, CurrentHeight, transform.position.z); Yaw = Input.GetAxis("Right Horizontal") * RotateSpeedPerTime; Pitch = Input.GetAxis("Right Vertical") * RotateSpeedPerTime; transform.Translate(new Vector3(Yaw, -Pitch, 0)); transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z); transform.LookAt(Target.transform); } }

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  • Multi Pass Blend

    - by Kirk Patrick
    I am seeking the simplest working example of a two pass HLSL pixel shader. It can do anything really, but the main idea is to perform "ping ponging" to take the output of the first pass and then send it for the second pass. In my example I want to draw to the R channel and then draw to the G channel and produce a simple Venn Diagram in the shader, but need to detect overlap. I can currently detect one or the other but not overlap. There are a red and green circle overlapping, and I want to put a dynamic texture map in the overlap region. I can currently put it in either or. Below is how it looks in the shader. -------------------------------- Texture2D shaderTexture; SamplerState SampleType; ////////////// // TYPEDEFS // ////////////// struct PixelInputType { float4 position : SV_POSITION; float2 tex0 : TEXCOORD0; float2 tex1 : TEXCOORD1; float4 color : COLOR; }; //////////////////////////////////////////////////////////////////////////////// // Pixel Shader //////////////////////////////////////////////////////////////////////////////// float4 main(PixelInputType input) : SV_TARGET { float4 textureColor0; float4 textureColor1; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor0 = shaderTexture.Sample(SampleType, input.tex0); textureColor1 = shaderTexture.Sample(SampleType, input.tex1); if (input.color[0]==1.0f && input.color[1]==1.0f) // Requires multi-pass textureColor0 = textureColor1; return textureColor0; } Here is the calling code (that needs to be modified) m_d3dContext->IASetVertexBuffers(0, 2, vbs, strides, offsets); m_d3dContext->IASetIndexBuffer(m_indexBuffer.Get(), DXGI_FORMAT_R32_UINT,0); m_d3dContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST); m_d3dContext->IASetInputLayout(m_inputLayout.Get()); m_d3dContext->VSSetShader(m_vertexShader.Get(), nullptr, 0); m_d3dContext->VSSetConstantBuffers(0, 1, m_constantBuffer.GetAddressOf()); m_d3dContext->PSSetShader(m_pixelShader.Get(), nullptr, 0); m_d3dContext->PSSetShaderResources(0, 1, m_SRV.GetAddressOf()); m_d3dContext->PSSetSamplers(0, 1, m_QuadsTexSamplerState.GetAddressOf());

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  • Typical collision detection

    - by marcg11
    I would like to know how is the typical collision detection of most games. For example, you control a character which can move in 2 dimensional directions (except up and down). Now lets asume he walks into a wall, most of the games depending on character angle and the BB normal face will only stop the player in one axis, but will continue moving in the other along the wall axis. How is that done? I've only managed to stop the character from going through the wall by seting the position to the last one in the past frame if the new position colllisions the bounding box. But this just makes the player stop sharply and unrealisticly.

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  • OpenGL ES 2.0 texture distortion on large geometry

    - by Spruce
    OpenGL ES 2.0 has serious precision issues with texture sampling - I've seen topics with a similar problem, but I haven't seen a real solution to this "distorted OpenGL ES 2.0 texture" problem yet. This is not related to the texture's image format or OpenGL color buffers, it seems like it's a precision error. I don't know what specifically causes the precision to fail - it doesn't seem like it's just the size of geometry that causes this distortion, because simply scaling vertex position passed to the the vertex shader does not solve the issue. Here are some examples of the texture distortion: Distorted Texture (on OpenGL ES 2.0): http://i47.tinypic.com/3322h6d.png What the texture normally looks like (also on OpenGL ES 2.0): http://i49.tinypic.com/b4jc6c.png The texture issue is limited to small scale geometry on OpenGL ES 2.0, otherwise the texture sampling appears normal, but the grainy effect gradually worsens the further the vertex data is from the origin of XYZ(0,0,0) These texture issues do not occur on desktop OpenGL (works fine under Windows XP, Windows 7, and Mac OS X) I've only seen the problem occur on Android, iPhone, or WebGL(which is similar to OpenGL ES 2.0) All textures are power of 2 but the problem still occurs Scaling the vertex data - The values of a vertex's X Y Z location are in the range of: -65536 to +65536 floating point I realized this was large, so I tried dividing the vertex positions by 1024 to shrink the geometry and hopefully get more accurate floating point precision, but this didn't fix or lessen the texture distortion issue Scaling the modelview or scaling the projection matrix does not help Changing texture filtering options does not help Disabling mipmapping, or using GL_NEAREST/GL_LINEAR does nothing Enabling/disabling anisotropic does nothing The banding effect still occurs even when using GL_CLAMP Dividing the texture coords passed to the vertex shader and then multiplying them back to the correct values in the fragment shader, also does not work precision highp sampler2D, highp float, highp int - in the fragment or the vertex shader didn't change anything (lowp/mediump did not work either) I'm thinking this problem has to have been solved at one point - Seeing that OpenGL ES 2.0 -based games have been able to render large-scale, highly detailed geometry

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  • yield – Just yet another sexy c# keyword?

    - by George Mamaladze
    yield (see NSDN c# reference) operator came I guess with .NET 2.0 and I my feeling is that it’s not as wide used as it could (or should) be.   I am not going to talk here about necessarity and advantages of using iterator pattern when accessing custom sequences (just google it).   Let’s look at it from the clean code point of view. Let's see if it really helps us to keep our code understandable, reusable and testable.   Let’s say we want to iterate a tree and do something with it’s nodes, for instance calculate a sum of their values. So the most elegant way would be to build a recursive method performing a classic depth traversal returning the sum.           private int CalculateTreeSum(Node top)         {             int sumOfChildNodes = 0;             foreach (Node childNode in top.ChildNodes)             {                 sumOfChildNodes += CalculateTreeSum(childNode);             }             return top.Value + sumOfChildNodes;         }     “Do One Thing” Nevertheless it violates one of the most important rules “Do One Thing”. Our  method CalculateTreeSum does two things at the same time. It travels inside the tree and performs some computation – in this case calculates sum. Doing two things in one method is definitely a bad thing because of several reasons: ·          Understandability: Readability / refactoring ·          Reuseability: when overriding - no chance to override computation without copying iteration code and vice versa. ·          Testability: you are not able to test computation without constructing the tree and you are not able to test correctness of tree iteration.   I want to spend some more words on this last issue. How do you test the method CalculateTreeSum when it contains two in one: computation & iteration? The only chance is to construct a test tree and assert the result of the method call, in our case the sum against our expectation. And if the test fails you do not know wether was the computation algorithm wrong or was that the iteration? At the end to top it all off I tell you: according to Murphy’s Law the iteration will have a bug as well as the calculation. Both bugs in a combination will cause the sum to be accidentally exactly the same you expect and the test will PASS. J   Ok let’s use yield! That’s why it is generally a very good idea not to mix but isolate “things”. Ok let’s use yield!           private int CalculateTreeSumClean(Node top)         {             IEnumerable<Node> treeNodes = GetTreeNodes(top);             return CalculateSum(treeNodes);         }             private int CalculateSum(IEnumerable<Node> nodes)         {             int sumOfNodes = 0;             foreach (Node node in nodes)             {                 sumOfNodes += node.Value;             }             return sumOfNodes;         }           private IEnumerable<Node> GetTreeNodes(Node top)         {             yield return top;             foreach (Node childNode in top.ChildNodes)             {                 foreach (Node currentNode in GetTreeNodes(childNode))                 {                     yield return currentNode;                 }             }         }   Two methods does not know anything about each other. One contains calculation logic another jut the iteration logic. You can relpace the tree iteration algorithm from depth traversal to breath trevaersal or use stack or visitor pattern instead of recursion. This will not influence your calculation logic. And vice versa you can relace the sum with product or do whatever you want with node values, the calculateion algorithm is not aware of beeng working on some tree or graph.  How about not using yield? Now let’s ask the question – what if we do not have yield operator? The brief look at the generated code gives us an answer. The compiler generates a 150 lines long class to implement the iteration logic.       [CompilerGenerated]     private sealed class <GetTreeNodes>d__0 : IEnumerable<Node>, IEnumerable, IEnumerator<Node>, IEnumerator, IDisposable     {         ...        150 Lines of generated code        ...     }   Often we compromise code readability, cleanness, testability, etc. – to reduce number of classes, code lines, keystrokes and mouse clicks. This is the human nature - we are lazy. Knowing and using such a sexy construct like yield, allows us to be lazy, write very few lines of code and at the same time stay clean and do one thing in a method. That's why I generally welcome using staff like that.   Note: The above used recursive depth traversal algorithm is possibly the compact one but not the best one from the performance and memory utilization point of view. It was taken to emphasize on other primary aspects of this post.

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  • Convex Hull for Concave Objects

    - by Lighthink
    I want to implement GJK and I want it to handle concave shapes too (almost all my shapes are concave). I've thought of decomposing the concave shape into convex shapes and then building a hierarchical tree out of convex shapes, but I do not know how to do it. Nothing I could find on the Internet about it wasn't satisfying my needs, so maybe someone can point me in the right direction or give a full explanation.

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  • How can I chose the depth of a quadtree?

    - by Evpok
    In a 2d world, using a quadtree to prune pairs in collision detection, how can I chose the depth of said quadtree? The world I am dealing with is mostly made of moving objects¹, so the cost of dispatching the objects between the quadtree cells matter. So what I am interested in is the balance between the gain from less collision checking and the loss from more dispatching. 1. To be completely explicit, autonomous self-replicating cells competing for food sources, in an attempt to show my pupils predator-prey dynamics and genetic evolution at work

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  • Staggered Isometric Map: Calculate map coordinates for point on screen

    - by Chris
    I know there are already a lot of resources about this, but I haven't found one that matches my coordinate system and I'm having massive trouble adjusting any of those solutions to my needs. What I learned is that the best way to do this is to use a transformation matrix. Implementing that is no problem, but I don't know in which way I have to transform the coordinate space. Here's an image that shows my coordinate system: How do I transform a point on screen to this coordinate system?

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  • Everything turning black when pitching down

    - by Gordon
    Just a quick questions about something that's occurring in my world. Every time I pitch my camera downward, everything starts turning black, and if I pitch upward, everything sort of intensifies. I'm multiplying my normals by the normal matrix in the shader, and I'm multiplying my lights direction by the model view matrix. If I leave the normal and light dir in world space everything ends up fine. I thought putting them both in view space would not cause those weird things to happen?

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  • Setting the values of a struct array from JS to GLSL

    - by mikidelux
    I've been trying to make a structure that will contain all the lights of my WebGL app, and I'm having troubles setting up it's values from JS. The structure is as follows: struct Light { vec4 position; vec4 ambient; vec4 diffuse; vec4 specular; vec3 spotDirection; float spotCutOff; float constantAttenuation; float linearAttenuation; float quadraticAttenuation; float spotExponent; float spotLightCosCutOff; }; uniform Light lights[numLights]; After testing LOTS of things I made it work but I'm not happy with the code I wrote: program.uniform.lights = []; program.uniform.lights.push({ position: "", diffuse: "", specular: "", ambient: "", spotDirection: "", spotCutOff: "", constantAttenuation: "", linearAttenuation: "", quadraticAttenuation: "", spotExponent: "", spotLightCosCutOff: "" }); program.uniform.lights[0].position = gl.getUniformLocation(program, "lights[0].position"); program.uniform.lights[0].diffuse = gl.getUniformLocation(program, "lights[0].diffuse"); program.uniform.lights[0].specular = gl.getUniformLocation(program, "lights[0].specular"); program.uniform.lights[0].ambient = gl.getUniformLocation(program, "lights[0].ambient"); ... and so on I'm sorry for making you look at this code, I know it's horrible but I can't find a better way. Is there a standard or recommended way of doing this properly? Can anyone enlighten me?

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  • Textures of .x model deformed in XNA

    - by marc wellman
    I want to have a 3D model with textures built in SketchUp 8 be imported as a .x model in XNA. So far I have used several .x exporters like http://edecadoudal.googlepages.com/xExporter.rb 3D RAD zbylsxexporter With all of them I have the same problem: The model gets built correctly but the textures are deformed. The sizes of my texture files are multiples of four and inside Sketchup the model looks prefect. That's the texture file which is 256x256: And this is how it looks like in my XNA program: What can I do?

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  • Unreal 3 Editor (Unreal Tournament 3) Why does the X Y Z translations now rotate along with my static meshes?

    - by Gareth Jones
    So I was making a map for UT3, using the Unreal 3 Editor provided, and all was going well. However I was doing some work with InterpActors and Vehicle Spawners, when I must have hit a key by mistake (or other wise somehow changed something) by mistake. Now the X Y Z translations that are used to move objects around in the editor will rotate along with the object (Ive put images down below to help show what I mean) - This is very annoying because it also changes the direction the arrow keys move a rotated object, in the example below, the Down arrow key will now move the object to the right. How can I fix this? (Note both images are taken from the same viewpoint) Before Rotation: After Rotation: P.S. If someone could please provide me with the correct / better name for the X Y Z "things" it would be much appreciated, thanks!

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  • How to create an extensible rope in Box2D?

    - by Thomas
    Let's say I'm trying to create a ninja lowering himself down a rope, or pulling himself back up, all whilst he might be swinging from side to side or hit by objects. Basically like http://ninja.frozenfractal.com/ but with Box2D instead of hacky JavaScript. Ideally I would like to use a rope joint in Box2D that allows me to change the length after construction. The standard Box2D RopeJoint doesn't offer that functionality. I've considered a PulleyJoint, connecting the other end of the "pulley" to an invisible kinematic body that I can control to change the length, but PulleyJoint is more like a rod than a rope: it constrains maximum length, but unlike RopeJoint it constrains the minimum as well. Re-creating a RopeJoint every frame using a new length is rather inefficient, and I'm not even sure it would work properly in the simulation. I could create a "chain" of bodies connected by RotationJoints but that is also less efficient, and less robust. I also wouldn't be able to change the length arbitrarily, but only by adding and removing a whole number of links, and it's not obvious how I would connect the remainder without violating existing joints. This sounds like something that should be straightforward to do. Am I overlooking something?

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  • How to achieve uniform speed of movement in cocos 2d?

    - by Andrey Chernukha
    I'm an absolute beginner in cocos2 , actually i started dealing with it yesterday. What i'm trying to do is moving an image along Bezier curve. This is how i do it - (void)startFly { [self runAction:[CCSequence actions: [CCBezierBy actionWithDuration:timeFlying bezier:[self getPathWithDirection:currentDirection]], [CCCallFuncN actionWithTarget:self selector:@selector(endFly)], nil]]; } My issue is that the image moves not uniformly. In the beginning it's moving slowly and then it accelerates gradually and at the end it's moving really fast. What should i do to get rid of this acceleration?

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  • I'm looking to learn how to apply traditional animation techniques to my graphics engine - are there any tutorials or online-resources that can help?

    - by blueberryfields
    There are many traditional animation techniques - such as blurring of motion, motion along an elliptical curve rather than a straight line, counter-motion before beginning of movement - which help with creating the appearance of a realistic 3D animated character. I'm looking to incorporate tools and short cuts for some of these into my graphics engine, to make it easier for my end users to use these techniques in their animations. Is there a good resource listing the techniques and the principles behind them, especially how they might apply to a graphics engine or 3D animation?

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  • Question about component based design: handling objects interaction

    - by Milo
    I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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