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• Ignore collisions with some objects in certain contexts

  - by Paul Manta

  I'm making a racing game with cars in Unity. The car has a boost/nitro powerup. While boosting, I wouldn't want to be deviated when colliding with zombies, but I do want to be deviated when colliding with walls. On the other hand, I don't want to ignore collision with zombies, because I still want to hit them on impact. How should I handle this? Basically, what I want is for the car to not rotate when colliding with certain objects.

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• Love2D engine for Lua; What about 3D?

  - by shadowprotocol

  Lua has been really awesome to learn, it's so simple. I really enjoy scripting languages, and I had an equally enjoyable time learning Python. The Love engine, http://love2d.org/, is really awesome, but I'm looking for something that can handle 3D as well. Is there anything that accommodates 3D in Lua? I'm still intrigued by the particle system of LOVE anyway and may just turn my idea into a 2D project with Particle lighting :) EDIT: I removed comments about Python - I want this to be a Lua topic. Thanks

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• Manually updating HTML5 local storage?

  - by hustlerinc

  I'm just starting out HTML5 game developement (and game dev in general) and watching all the videos and tutorials available something has crossed my mind. Everyone keep saying I should set the cookie's (or cached files) to be expired after a certain amount of time. So that when it reaches that time the browser automatically downloads all assets again, even if it's the same asset's. Wouldn't it be possible to manually define the version of the game? For example the user has downloaded all the files for 1.01 of the game, when updating I change a simple variable to 1.02. When the user logs in it would compare his version to the current and if they are not equal only then it downloads the files? This could even be improved to download only specific files depending on what needs to be updated? Would this be possible or am I just dreaming? What are the possible downsides of this approach?

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• How to send multiple MVP matrices to a vertex shader in OpenGL ES 2.0

  - by Carbon Crystal

  I'm working my way through optimizing the rendering of sprites in a 2D game using OpenGL ES and I've hit the limit of my knowledge when it comes to GLSL and vertex shaders. I have two large float buffers containing my vertex coordinates and texture coordinates (eventually this will be one buffer) for multiple sprites in order to perform a single glDrawArrays call. This works but I've hit a snag when it comes to passing the transformation matrix into the vertex shader. My shader code is: uniform mat4 u_MVPMatrix; attribute vec4 a_Position; attribute vec2 a_TexCoordinate; varying vec2 v_TexCoordinate; void main() { v_TexCoordinate = a_TexCoordinate; gl_Position = u_MVPMatrix * a_Position; } In Java (Android) I am using a FloatBuffer to store the vertex/texture data and this is provided to the shader like so: mGlEs20.glVertexAttribPointer(mVertexHandle, Globals.GL_POSITION_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mVertexCoordinates); mGlEs20.glVertexAttribPointer(mTextureCoordinateHandle, Globals.GL_TEXTURE_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mTextureCoordinates); (The Globals.GL_POSITION_VERTEX_COUNT etc are just integers with the value of 2 right now) And I'm passing the MVP (Model/View/Projection) matrix buffer like this: GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mModelCoordinates); (mModelCoordinates is a FloatBuffer containing 16-float sequences representing the MVP matrix for each sprite) This renders my scene but all the sprites share the same transformation, so it's obviously only picking the first 16 elements from the buffer which makes sense since I am passing in "1" as the second parameter. The documentation for this method says: "This should be 1 if the targeted uniform variable is not an array of matrices, and 1 or more if it is an array of matrices." So I tried modifying the shader with a fixed size array large enough to accomodate most of my scenarios: uniform mat4 u_MVPMatrix[1000]; But this lead to an error in the shader: cannot convert from 'uniform array of 4X4 matrix of float' to 'Position 4-component vector of float' This just seems wrong anyway as it's not clear to me how the shader would know when to transition to the next matrix anyway. Anyone have an idea how I can get my shader to pick up a different MVP matrix (i.e. the NEXT 16 floats) from my MVP buffer for every 4 vertices it encounters? (I am using GL_TRIANGLE_STRIP so each sprite has 4 vertices). Thanks!

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• Beginner C# image loading woes - NullReferenceException

  - by Seth Taddiken

  I keep getting a "NullReferenceExeption was unhandled" with "Object reference not set to an instance of an object." written under it. I have all of the images (png) correct with names and added to references. protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); backGround = Content.Load<Texture2D>("Cracked"); player1.playerBlock = Content.Load<Texture2D>("square"); player2.playerBlock = Content.Load<Texture2D>("square2"); }

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• Behaviour Trees with irregular updates

  - by Robominister

  I'm interested in behaviour trees that aren't iterated every game tick, but every so often. (Edit: the tree could specify how many frames within the main game loop to wait before running its tick function again). Every theoretical implementation I have seen of behaviour trees talks of the tree search being carried out every game update - which seems necessary, because a leaf node (eg a behaviour, like 'return to base') needs to be constantly checked to see if is still running, failed or completed. Can anyone suggest how I might start implementing a tree that isnt run every tick, or point me in the direction of good material specific to this case (I am struggling to find anything)? My thoughts so far: action leaf nodes (when they start) must only push some kind of action object onto a list for an entity, rather than directly calling any code that makes the entity do something. The list of actions for the entity would be run every frame (update any that need to run, pop any that have completed from the list). the return state from a given action must be fed back into the tree, so that when we run the tree iteration again (and reach the same action leaf node - so the tree has so far determined that we ought to still be trying this action) - that the action has completed, or is still running etc. If my actual action code is running from an action list on an entity, then I possibly need to cancel previously running actions in the list - i am thinking that I can just delete the entire stack of queued up actions. I've seen the idea of ActionLists which block lower priority actions when a higher priority one is added, but this seems like very close logic to behaviour trees, and I dont want to be duplicating behaviour. This leaves me with some questions 1) How would I feed the action return state back into the tree? Its obvious I need to store some information relating to 'currently executing actions' on the entity, and check that in the tree tick, but I can't imagine how. 2) Does having a seperate behaviour tree (for deciding behaviour) and action list (for carrying out actual queued up actions) sound like a reasonable approach? 3) Is the approach of updating a behaviour tree irregularly actually used by anyone? It seems like a nice idea for budgeting ai search time when you have a lot of ai entities to process. (Edit) - I am also thinking about storing a single instance of a given behaviour tree in memory, and providing it by reference to any entity that uses it. So any information about what action was last selected for execution on an entity must be stored in a data context relative to the entity (which the tree can check). (I am probably answering my own questions as i go!) I hope I have expressed my questions adequately! Thanks in advance for any help :)

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• Which will be faster? Switching shaders or ignore that some cases don't need full code?

  - by PolGraphic

  I have two types of 2d objects: In first case (for about 70% of objects), I need that code in the shader: float2 texCoord = input.TexCoord + textureCoord.xy But in the second case I have to use: float2 texCoord = fmod(input.TexCoord, texCoordM.xy - textureCoord.xy) + textureCoord.xy I can use second code also for first case, but it will be a little slower (fmod is useless here, input.TexCoord will be always lower than textureCoord.xy - textureCoord.xy for sure). My question is, which way will be faster: Making two independent shaders for both types of rectangles, group rectangles by types and switch shaders during rendering. Make one shader and use some if statement. Make one shader and ignore that sometimes (70% of cases) I don't need to use fmod.

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• MCP 1.7.10 Java class navigation

  - by Elias Benevedes

  So, I'm new to the Minecraft modding community and trying to understand where to start. I've attempted to do it before, but dropped it to the complexity of starting and the lack of a site like this to help (Mind that I'm also semi-new to Java, but have worked extensively in Javascript and Python. I understand how Java is different from the two). I have downloaded MCP 9.08 (Decompiles 1.7.10), and decompiled Minecraft. I'm looking to mod client, so I didn't supply it with a server jar. Everything seemed to work fine in decompile (Only error was it couldn't find the server jar). I can find my files in /mcp908/src/minecraft/net/minecraft. However, if I open up one of the classes in, say, block, I see a bunch of variables starting with p_ and ending with _. Is there any way to make these variables more decipherable, to understand what's going on so I can learn by example? Thank you.

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• Make objects slide across the screen in random positions

  - by user3475907

  I want to make an object appear randomly at the right hand side of the screen and then slide across the screen and disapear at the left hand side. I am working with libgdx. I have this bit of code but it makes items fall from the top down. Please help. public EntityManager(int amount, OrthoCamera camera) { player = new Player(new Vector2(15, 230), new Vector2(0, 0), this, camera); for (int i = 0; i < amount; i++) { float x = MathUtils.random(0, MainGame.HEIGHT - TextureManager.ENEMY.getHeight()); float y = MathUtils.random(MainGame.WIDTH, MainGame.WIDTH * 10); float speed = MathUtils.random(2, 10); addEntity(new Enemy(new Vector2(x, y), new Vector2(-0, -speed))); }

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• Best way to implement a simple bullet trajectory

  - by AirieFenix

  I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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• How do they keep track of the NPCs in Left 4 Dead?

  - by f20k

  How do they keep track of the NPC zombies in Left 4 Dead? I am talking about the NPCs that just walk into walls or wander around aimlessly. Even though the players cannot see them, they are there (say inside rooms or behind doors). Let's say there's about 10 or so zombies in a hallway and inside rooms. Does the game keep all of those zombies in a list and iterate through giving them commands? Do they just spawn when the user is within a certain radius or reached a special location? Say you placed the 4 units (controlled by players) on completely different places throughout the map. Let's assume you aren't being swarmed and then you have not killed any of these aimless NPCs. Would the game be keeping track of 10 x 4 = 40 zombies in total? Or is my understanding completely off? The reason I ask is if I were to implement something similar on a mobile device, keeping track of 40 or more NPCs might not be such a great idea.

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• Hydraulics in game

  - by Mungoid

  I'm not completely sure if this would be better in the Physics site or not as this question is more about how hydraulics should work in game as opposed to how they really work (although that is taken into account) - So I apologize if this is in the wrong place. A project we are on, we have a machine with hydraulics that are powered (They don't just look like they move something, they are the only thing moving/turning/lifting something) - However, the hydraulic extends the same speed no matter what it is pushing. So, say there is a 10 ton object attached to one end of the hydraulic and the other end is attached to a plate on the ground. In real life it takes a few seconds to build up pressure depending on how heavy the object is, but in our project the hydraulics don't care about that. It will lift a 100 ton object the same speed as a 10 ton object. We have a way to fake the hydraulic pressurizing by reducing the 'drive amount' (how fast or slow the hydraulic extends) when we sense that it is touching the ground and that does a relatively decent job but we would like to be able to take other things into account like engine speed, ratios, loads, etc. but we aren't too sure what we need to think about. I'm kinda wondering if anyone here has any experience with this and could offer some suggestions on what to take into account?

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• write to depth buffer while using multiple render targets

  - by DocSeuss

  Presently my engine is set up to use deferred shading. My pixel shader output struct is as follows: struct GBuffer { float4 Depth : DEPTH0; //depth render target float4 Normal : COLOR0; //normal render target float4 Diffuse : COLOR1; //diffuse render target float4 Specular : COLOR2; //specular render target }; This works fine for flat surfaces, but I'm trying to implement relief mapping which requires me to manually write to the depth buffer to get correct silhouettes. MSDN suggests doing what I'm already doing to output to my depth render target - however, this has no impact on z culling. I think it might be because XNA uses a different depth buffer for every RenderTarget2D. How can I address these depth buffers from the pixel shader?

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• Resolving collisions between dynamic game objects

  - by TheBroodian

  I've been building a 2D platformer for some time now, I'm getting to the point where I am adding dynamic objects to the stage for testing. This has prompted me to consider how I would like my character and other objects to behave when they collide. A typical staple in many 2D platformer type games is that the player takes damage upon touching an enemy, and then essentially becomes able to pass through enemies during a period of invulnerability, and at the same time, enemies are able to pass through eachother freely. I personally don't want to take this approach, it feels strange to me that the player should receive arbitrary damage for harmless contact to an enemy, despite whether the enemy is attacking or not, and I would like my enemies' interactions between each other (and my player) to be a little more organic, so to speak. In my head I sort of have this idea where a game object (player, or non player) would be able to push other game objects around by manner of 'pushing' each other out of one anothers' bounding boxes if there is an intersection, and maybe correlate the repelling force to how much their bounding boxes are intersecting. The problem I'm experiencing is I have no idea what the math might look like for something like this? I'll show what work I've done so far, it sort of works, but it's jittery, and generally not quite what I would pass in a functional game: //Clears the anti-duplicate buffer collisionRecord.Clear(); //pick a thing foreach (GameObject entity in entities) { //pick another thing foreach (GameObject subject in entities) { //check to make sure both things aren't the same thing if (!ReferenceEquals(entity, subject)) { //check to see if thing2 is in semi-near proximity to thing1 if (entity.WideProximityArea.Intersects(subject.CollisionRectangle) || entity.WideProximityArea.Contains(subject.CollisionRectangle)) { //check to see if thing2 and thing1 are colliding. if (entity.CollisionRectangle.Intersects(subject.CollisionRectangle) || entity.CollisionRectangle.Contains(subject.CollisionRectangle) || subject.CollisionRectangle.Contains(entity.CollisionRectangle)) { //check if we've already resolved their collision or not. if (!collisionRecord.ContainsKey(entity.GetHashCode())) { //more duplicate resolution checking. if (!collisionRecord.ContainsKey(subject.GetHashCode())) { //if thing1 is traveling right... if (entity.Velocity.X > 0) { //if it isn't too far to the right... if (subject.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height)) || subject.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(entity.CollisionRectangle.Right, entity.CollisionRectangle.Y, 1, entity.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = entity.CollisionRectangle.Right - subject.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the left, and thing2 to the right. entity.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //if thing1 is traveling left... if (entity.Velocity.X < 0) { //if thing1 isn't too far left... if (entity.CollisionRectangle.Contains(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height)) || entity.CollisionRectangle.Intersects(new Microsoft.Xna.Framework.Rectangle(subject.CollisionRectangle.Right, subject.CollisionRectangle.Y, 1, subject.CollisionRectangle.Height))) { //Find how deep thing1 is intersecting thing2's collision box; float offset = subject.CollisionRectangle.Right - entity.CollisionRectangle.Left; //Move both things in opposite directions half the length of the intersection, pushing thing1 to the right, and thing2 to the left. entity.Velocities.Add(new Vector2((((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); subject.Velocities.Add(new Vector2(-(((offset * 4) * (float)gameTime.ElapsedGameTime.TotalMilliseconds)), 0)); } } //Make record that thing1 and thing2 have interacted and the collision has been solved, so that if thing2 is picked next in the foreach loop, it isn't checked against thing1 a second time before the next update. collisionRecord.Add(entity.GetHashCode(), subject.GetHashCode()); } } } } } } } } One of the biggest issues with my code aside from the jitteriness is that if one character were to land on top of another character, it very suddenly and abruptly resolves the collision, whereas I would like a more subtle and gradual resolution. Any thoughts or ideas are incredibly welcome and helpful.

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• Efficient way to calculate "vision cones" on 2D tile map?

  - by OverMachoGrande

  I'm trying to calculate which tiles a particular unit can "see" if facing a certain direction on a tile map (within a certain range and angle of facing). The easiest way would be to draw a certain number of tiles outward and raycast to each tile. However, I'm hoping for something slightly more efficient. A picture says a thousand words: The red dot is the unit (who's facing upwards). My goal is to calculate the yellow tiles. The green blocks are walls (walls are between tiles, and it's easy to check if you can pass between two tiles). The blue line represents something like the "raycasting" method I was talking about, but I'd rather not have to do this. EDIT: Units can only be facing north/south/east/west (0, 90, 180, or 270 degrees) and FoV is always 90 degrees. Should simplify some calculations. I'm thinking there's some sort of recursive-ish/stack-based/queue-based algorithm, but I can't quite figure it out. Thanks!

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• Detecting walls or floors in pygame

  - by Serial

  I am trying to make bullets bounce of walls, but I can't figure out how to correctly do the collision detection. What I am currently doing is iterating through all the solid blocks and if the bullet hits the bottom, top or sides, its vector is adjusted accordingly. However, sometimes when I shoot, the bullet doesn't bounce, I think it's when I shoot at a border between two blocks. Here is the update method for my Bullet class: def update(self, dt): if self.can_bounce: #if the bullet hasnt bounced find its vector using the mousclick pos and player pos speed = -10. range = 200 distance = [self.mouse_x - self.player[0], self.mouse_y - self.player[1]] norm = math.sqrt(distance[0] ** 2 + distance[1] ** 2) direction = [distance[0] / norm, distance[1 ] / norm] bullet_vector = [direction[0] * speed, direction[1] * speed] self.dx = bullet_vector[0] self.dy = bullet_vector[1] #check each block for collision for block in self.game.solid_blocks: last = self.rect.copy() if self.rect.colliderect(block): topcheck = self.rect.top < block.rect.bottom and self.rect.top > block.rect.top bottomcheck = self.rect.bottom > block.rect.top and self.rect.bottom < block.rect.bottom rightcheck = self.rect.right > block.rect.left and self.rect.right < block.rect.right leftcheck = self.rect.left < block.rect.right and self.rect.left > block.rect.left each test tests if it hit the top bottom left or right side of the block its colliding with if self.can_bounce: if topcheck: self.rect = last self.dy *= -1 self.can_bounce = False print "top" if bottomcheck: self.rect = last self.dy *= -1 #Bottom check self.can_bounce = False print "bottom" if rightcheck: self.rect = last self.dx *= -1 #right check self.can_bounce = False print "right" if leftcheck: self.rect = last self.dx *= -1 #left check self.can_bounce = False print "left" else: # if it has already bounced and colliding again kill it self.kill() for enemy in self.game.enemies_list: if self.rect.colliderect(enemy): self.kill() #update position self.rect.x -= self.dx self.rect.y -= self.dy This definitely isn't the best way to do it but I can't think of another way. If anyone has done this or can help that would be awesome!

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• Rotating a child shape relative to its parent's orientation

  - by user1423893

  When rotating a shape using a quaternion value I also wish rotate its child shape. The parent and child shapes both start with different orientations but their relative orientations should always be the same. How can I use the difference between the previous and current quaternions of the parent shape in order to transform the child segment and rotate it relative to its parent shape? public Quaternion Orientation { get { return entity.Orientation; } set { Quaternion previousValue = entity.Orientation; entity.Orientation = value; // Use the difference between the quaternion values to update child orientation } }

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• Game Input mouse filtering

  - by aaron

  I'm having a problem with filtering mouse inputs, the method I am doing right know moves the cursor back to the center of the screen each frame. But I cant do this because it messes with other things. Does anyone know how to implement this with delta mouse movement. Here is the relevant code. void update() { static float oldX = 0; static float oldY = 0; static float walkSpeed = .05f; static float sensitivity = 0.002f;//mouse sensitivity static float smooth = 0.7f;//mouse smoothing (0.0 - 0.99) float w = ScreenResolution.x/2.0f; float h = ScreenResolution.y/2.0f; Vec2f scrc(w,h); Vec2f mpos(getMouseX(),getMouseY()); float x = scrc.x-mpos.x; float y = scrc.y-mpos.y; oldX = (oldX*smooth + x*(1.0-smooth)); oldY = (oldY*smooth + y*(1.0-smooth)); x = oldX * sensitivity; y = oldY * sensitivity; camera->rotate(Vec3f(y,0,0)); transform->setRotation(transform->getRotation()*Quaternionf::fromAxisAngle(0.0f,1.0f,0.0f,-x)); setMousePosition((int)scrc.x,(int)scrc.y);//THIS IS THE PROBLEM LINE HOW CAN I AVOID THIS .... }

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• IDirect3DDevice9Ex and D3DPOOL_MANAGED?

  - by bluescrn

  So I wanted to switch to IDirect3DDevice9Ex, purely for the SetFrameLatency function, as fullscreen vsynced D3D seemed to produce noticable input lag. But then it tells me 'ha ha ha! now you can't use D3DPOOL_MANAGED!': Direct3D9: (ERROR) :D3DPOOL_MANAGED is not valid with IDirect3DDevice9Ex Is this really as unpleasant as it looks (when you're relying quite heavily on managed resources) - or is there a simple solution? If it really does mean manual management of everything (reloading all static textures, VBs, and IBs on a device reset), is it worth the hassle, will IDirect3DDevice9Ex bring enough benefit to make it worth writing a new resource manager? Starting to think I must be doing something wrong, due to this: Direct3D9: (ERROR) :Lock is not supported for textures allocated with POOL_DEFAULT unless they are marked D3DUSAGE_DYNAMIC. So if I put my (static) textures in POOL_DEFAULT, they need flagging as D3DUSAGE_DYNAMIC, just because I lock them once to load the data in?

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• scaling point sprites with distance

  - by Will

  How can you scale a point sprite by its distance from the camera? GLSL fragment shader: gl_PointSize = size / gl_Position.w; seems along the right tracks; for any given scene all sprites seem nicely scaled by distance. Is this correct? How do you compute the proper scaling for my vertex attribute size? I want each sprite to be scaled by the modelview matrix. I had played with arbitrary values and it seems that size is the radius in pixels at the camera, and is not in modelview scale. I've also tried: gl_Position = pMatrix * mvMatrix * vec4(vertex,1.0); vec4 v2 = pMatrix * mvMatrix * vec4(vertex.x,vertex.y+0.5*size,vertex.z,1.0); gl_PointSize = length(gl_Position.xyz-v2.xyz) * gl_Position.w; But this makes the sprites be bigger in the distance, rather than smaller:

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• Calculating up-vector to avoid gimbal lock using euler angles

  - by jessejuicer

  I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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• Simple Math Multiplayer game - is Ajax sufficient?

  - by Christian Strang

  I'm planning to create a simple math multiplayer game and I plan to just use Ajax for the server/client communication but I'm not sure if this is sufficient or if I need a socket server. The game will look like this: 2-4 users all get a simple math task (like: "37 + 14") they have to solve it as fast as possible first user who solves it is the winner I will track the time for each user, since the game started, on the client side and everytime a user gives an answer, the answer and the passed time will be send to the server. Additionally I'll add a function which will check every 3 seconds if the other users finished, how much time they needed and who won. Do you think this is possible just using Ajax? What alternatives are there?

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• Moving 2d camera in the y direction

  - by Alex

  I'm developing a simple game for the iphone and am struggling to work out the best way for the camera to follow the main character. The following picture hightlights the three main components: There are 3 components to this: Circle - the main character Green line - terrain Black background The terrain is simply made from an array of points (approx 20 points per screen width). The terrain is moved in the x direction relative to the black background in order to keep the circle in its position shown. The distance to move the terrain is simply: movex = circle.position.x - terrain.position.x with a constant to fix the circle at some distance from the left of the screen. I am struggling to determine the best way to position the terrain in the y plane keep the focus in the character. I want to move the terrain in the y direction smoothly and not fix it to the position of the circle, so the circle can move in the y plane. If I take the same approach as the x positioning, the character is fixed at a point on the screen and the terrain moves. I could sample some terrain points either side of the character and produce an average, but in my implementation this was not smooth. I thought another approach might be to create a camera 'line' that is a smooth version of the terrain line and make the camerea follow this, but I'm not sure if this is the optimum solution. Any advice is much appreciated!

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• Confusion about Rotation matrices from Euler Angles

  - by xEnOn

  I am trying to learn more about Euler Angles so as to help myself in understanding how I can control my camera better in the game. I came across the following formula that converts Euler Angles to rotation matrices: In the equation, I could see that the first matrix from the left is the rotation matrix about x-axis, the second is about y-axis and the third is about z-axis. From my understanding about ordinary matrix transformations, the later transformation is always applied to the right hand side. And if I'm right about this, then the above equation should have a rotation order starting from rotating about z-axis, y-axis, then finally x-axis. But, from the symbols it seems that the rotation order start rotating about x-axis, then y-axis, then finally z-axis. What should the actual order of the rotation be? Also, I am confuse about if the input vector, in this case, would be a row vector on the left, or a column vector on the right?

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• Camera doesn't move

  - by hugo

  Here is my code, as my subject indicates i have implemented a camera but I couldn't make it move. #define PI_OVER_180 0.0174532925f #define GL_CLAMP_TO_EDGE 0x812F #include "metinalifeyyaz.h" #include <GL/glu.h> #include <GL/glut.h> #include <QTimer> #include <cmath> #include <QKeyEvent> #include <QWidget> #include <QDebug> metinalifeyyaz::metinalifeyyaz(QWidget *parent) : QGLWidget(parent) { this->setFocusPolicy(Qt:: StrongFocus); time = QTime::currentTime(); timer = new QTimer(this); timer->setSingleShot(true); connect(timer, SIGNAL(timeout()), this, SLOT(updateGL())); xpos = yrot = zpos = 0; walkbias = walkbiasangle = lookupdown = 0.0f; keyUp = keyDown = keyLeft = keyRight = keyPageUp = keyPageDown = false; } void metinalifeyyaz::drawBall() { //glTranslatef(6,0,4); glutSolidSphere(0.10005,300,30); } metinalifeyyaz:: ~metinalifeyyaz(){ glDeleteTextures(1,texture); } void metinalifeyyaz::initializeGL(){ glShadeModel(GL_SMOOTH); glClearColor(1.0,1.0,1.0,0.5); glClearDepth(1.0f); glEnable(GL_DEPTH_TEST); glEnable(GL_TEXTURE_2D); glDepthFunc(GL_LEQUAL); glClearColor(1.0,1.0,1.0,1.0); glShadeModel(GL_SMOOTH); GLfloat mat_specular[]={1.0,1.0,1.0,1.0}; GLfloat mat_shininess []={30.0}; GLfloat light_position[]={1.0,1.0,1.0}; glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular); glMaterialfv(GL_FRONT,GL_SHININESS,mat_shininess); glLightfv(GL_LIGHT0, GL_POSITION, light_position); glEnable(GL_LIGHT0); glEnable(GL_LIGHTING); QImage img1 = convertToGLFormat(QImage(":/new/prefix1/halisaha2.bmp")); QImage img2 = convertToGLFormat(QImage(":/new/prefix1/white.bmp")); glGenTextures(2,texture); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img1.width(), img1.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img1.bits()); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img2.width(), img2.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img2.bits()); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really nice perspective calculations } void metinalifeyyaz::resizeGL(int w, int h){ if(h==0) h=1; glViewport(0,0,w,h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f, static_cast<GLfloat>(w)/h,0.1f,100.0f); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } void metinalifeyyaz::paintGL(){ movePlayer(); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); GLfloat xtrans = -xpos; GLfloat ytrans = -walkbias - 0.50f; GLfloat ztrans = -zpos; GLfloat sceneroty = 360.0f - yrot; glLoadIdentity(); glRotatef(lookupdown, 1.0f, 0.0f, 0.0f); glRotatef(sceneroty, 0.0f, 1.0f, 0.0f); glTranslatef(xtrans, ytrans+50, ztrans-130); glLoadIdentity(); glTranslatef(1.0f,0.0f,-18.0f); glRotatef(45,1,0,0); drawScene(); int delay = time.msecsTo(QTime::currentTime()); if (delay == 0) delay = 1; time = QTime::currentTime(); timer->start(qMax(0,10 - delay)); } void metinalifeyyaz::movePlayer() { if (keyUp) { xpos -= sin(yrot * PI_OVER_180) * 0.5f; zpos -= cos(yrot * PI_OVER_180) * 0.5f; if (walkbiasangle >= 360.0f) walkbiasangle = 0.0f; else walkbiasangle += 7.0f; walkbias = sin(walkbiasangle * PI_OVER_180) / 10.0f; } else if (keyDown) { xpos += sin(yrot * PI_OVER_180)*0.5f; zpos += cos(yrot * PI_OVER_180)*0.5f ; if (walkbiasangle <= 7.0f) walkbiasangle = 360.0f; else walkbiasangle -= 7.0f; walkbias = sin(walkbiasangle * PI_OVER_180) / 10.0f; } if (keyLeft) yrot += 0.5f; else if (keyRight) yrot -= 0.5f; if (keyPageUp) lookupdown -= 0.5; else if (keyPageDown) lookupdown += 0.5; } void metinalifeyyaz::keyPressEvent(QKeyEvent *event) { switch (event->key()) { case Qt::Key_Escape: close(); break; case Qt::Key_F1: setWindowState(windowState() ^ Qt::WindowFullScreen); break; default: QGLWidget::keyPressEvent(event); case Qt::Key_PageUp: keyPageUp = true; break; case Qt::Key_PageDown: keyPageDown = true; break; case Qt::Key_Left: keyLeft = true; break; case Qt::Key_Right: keyRight = true; break; case Qt::Key_Up: keyUp = true; break; case Qt::Key_Down: keyDown = true; break; } } void metinalifeyyaz::changeEvent(QEvent *event) { switch (event->type()) { case QEvent::WindowStateChange: if (windowState() == Qt::WindowFullScreen) setCursor(Qt::BlankCursor); else unsetCursor(); break; default: break; } } void metinalifeyyaz::keyReleaseEvent(QKeyEvent *event) { switch (event->key()) { case Qt::Key_PageUp: keyPageUp = false; break; case Qt::Key_PageDown: keyPageDown = false; break; case Qt::Key_Left: keyLeft = false; break; case Qt::Key_Right: keyRight = false; break; case Qt::Key_Up: keyUp = false; break; case Qt::Key_Down: keyDown = false; break; default: QGLWidget::keyReleaseEvent(event); } } void metinalifeyyaz::drawScene(){ glBegin(GL_QUADS); glNormal3f(0.0f,0.0f,1.0f); // glColor3f(0,0,1); //back glVertex3f(-6,0,-4); glVertex3f(-6,-0.5,-4); glVertex3f(6,-0.5,-4); glVertex3f(6,0,-4); glEnd(); glBegin(GL_QUADS); glNormal3f(0.0f,0.0f,-1.0f); //front glVertex3f(6,0,4); glVertex3f(6,-0.5,4); glVertex3f(-6,-0.5,4); glVertex3f(-6,0,4); glEnd(); glBegin(GL_QUADS); glNormal3f(-1.0f,0.0f,0.0f); // glColor3f(0,0,1); //left glVertex3f(-6,0,4); glVertex3f(-6,-0.5,4); glVertex3f(-6,-0.5,-4); glVertex3f(-6,0,-4); glEnd(); glBegin(GL_QUADS); glNormal3f(1.0f,0.0f,0.0f); // glColor3f(0,0,1); //right glVertex3f(6,0,-4); glVertex3f(6,-0.5,-4); glVertex3f(6,-0.5,4); glVertex3f(6,0,4); glEnd(); glBindTexture(GL_TEXTURE_2D, texture[0]); glBegin(GL_QUADS); glNormal3f(0.0f,1.0f,0.0f);//top glTexCoord2f(1.0f,0.0f); glVertex3f(6,0,-4); glTexCoord2f(1.0f,1.0f); glVertex3f(6,0,4); glTexCoord2f(0.0f,1.0f); glVertex3f(-6,0,4); glTexCoord2f(0.0f,0.0f); glVertex3f(-6,0,-4); glEnd(); glBegin(GL_QUADS); glNormal3f(0.0f,-1.0f,0.0f); //glColor3f(0,0,1); //bottom glVertex3f(6,-0.5,-4); glVertex3f(6,-0.5,4); glVertex3f(-6,-0.5,4); glVertex3f(-6,-0.5,-4); glEnd(); // glPushMatrix(); glBindTexture(GL_TEXTURE_2D, texture[1]); glBegin(GL_QUADS); glNormal3f(1.0f,0.0f,0.0f); glTexCoord2f(1.0f,0.0f); //right far goal post front face glVertex3f(5,0.5,-0.95); glTexCoord2f(1.0f,1.0f); glVertex3f(5,0,-0.95); glTexCoord2f(0.0f,1.0f); glVertex3f(5,0,-1); glTexCoord2f(0.0f,0.0f); glVertex3f(5, 0.5, -1); glColor3f(1,1,1); //right far goal post back face glVertex3f(5.05,0.5,-0.95); glVertex3f(5.05,0,-0.95); glVertex3f(5.05,0,-1); glVertex3f(5.05, 0.5, -1); glColor3f(1,1,1); //right far goal post left face glVertex3f(5,0.5,-1); glVertex3f(5,0,-1); glVertex3f(5.05,0,-1); glVertex3f(5.05, 0.5, -1); glColor3f(1,1,1); //right far goal post right face glVertex3f(5.05,0.5,-0.95); glVertex3f(5.05,0,-0.95); glVertex3f(5,0,-0.95); glVertex3f(5, 0.5, -0.95); glColor3f(1,1,1); //right near goal post front face glVertex3f(5,0.5,0.95); glVertex3f(5,0,0.95); glVertex3f(5,0,1); glVertex3f(5,0.5, 1); glColor3f(1,1,1); //right near goal post back face glVertex3f(5.05,0.5,0.95); glVertex3f(5.05,0,0.95); glVertex3f(5.05,0,1); glVertex3f(5.05,0.5, 1); glColor3f(1,1,1); //right near goal post left face glVertex3f(5,0.5,1); glVertex3f(5,0,1); glVertex3f(5.05,0,1); glVertex3f(5.05,0.5, 1); glColor3f(1,1,1); //right near goal post right face glVertex3f(5.05,0.5,0.95); glVertex3f(5.05,0,0.95); glVertex3f(5,0,0.95); glVertex3f(5,0.5, 0.95); glColor3f(1,1,1); //right crossbar front face glVertex3f(5,0.55,-1); glVertex3f(5,0.55,1); glVertex3f(5,0.5,1); glVertex3f(5,0.5,-1); glColor3f(1,1,1); //right crossbar back face glVertex3f(5.05,0.55,-1); glVertex3f(5.05,0.55,1); glVertex3f(5.05,0.5,1); glVertex3f(5.05,0.5,-1); glColor3f(1,1,1); //right crossbar bottom face glVertex3f(5.05,0.5,-1); glVertex3f(5.05,0.5,1); glVertex3f(5,0.5,1); glVertex3f(5,0.5,-1); glColor3f(1,1,1); //right crossbar top face glVertex3f(5.05,0.55,-1); glVertex3f(5.05,0.55,1); glVertex3f(5,0.55,1); glVertex3f(5,0.55,-1); glColor3f(1,1,1); //left far goal post front face glVertex3f(-5,0.5,-0.95); glVertex3f(-5,0,-0.95); glVertex3f(-5,0,-1); glVertex3f(-5, 0.5, -1); glColor3f(1,1,1); //right far goal post back face glVertex3f(-5.05,0.5,-0.95); glVertex3f(-5.05,0,-0.95); glVertex3f(-5.05,0,-1); glVertex3f(-5.05, 0.5, -1); glColor3f(1,1,1); //right far goal post left face glVertex3f(-5,0.5,-1); glVertex3f(-5,0,-1); glVertex3f(-5.05,0,-1); glVertex3f(-5.05, 0.5, -1); glColor3f(1,1,1); //right far goal post right face glVertex3f(-5.05,0.5,-0.95); glVertex3f(-5.05,0,-0.95); glVertex3f(-5,0,-0.95); glVertex3f(-5, 0.5, -0.95); glColor3f(1,1,1); //left near goal post front face glVertex3f(-5,0.5,0.95); glVertex3f(-5,0,0.95); glVertex3f(-5,0,1); glVertex3f(-5,0.5, 1); glColor3f(1,1,1); //right near goal post back face glVertex3f(-5.05,0.5,0.95); glVertex3f(-5.05,0,0.95); glVertex3f(-5.05,0,1); glVertex3f(-5.05,0.5, 1); glColor3f(1,1,1); //right near goal post left face glVertex3f(-5,0.5,1); glVertex3f(-5,0,1); glVertex3f(-5.05,0,1); glVertex3f(-5.05,0.5, 1); glColor3f(1,1,1); //right near goal post right face glVertex3f(-5.05,0.5,0.95); glVertex3f(-5.05,0,0.95); glVertex3f(-5,0,0.95); glVertex3f(-5,0.5, 0.95); glColor3f(1,1,1); //left crossbar front face glVertex3f(-5,0.55,-1); glVertex3f(-5,0.55,1); glVertex3f(-5,0.5,1); glVertex3f(-5,0.5,-1); glColor3f(1,1,1); //right crossbar back face glVertex3f(-5.05,0.55,-1); glVertex3f(-5.05,0.55,1); glVertex3f(-5.05,0.5,1); glVertex3f(-5.05,0.5,-1); glColor3f(1,1,1); //right crossbar bottom face glVertex3f(-5.05,0.5,-1); glVertex3f(-5.05,0.5,1); glVertex3f(-5,0.5,1); glVertex3f(-5,0.5,-1); glColor3f(1,1,1); //right crossbar top face glVertex3f(-5.05,0.55,-1); glVertex3f(-5.05,0.55,1); glVertex3f(-5,0.55,1); glVertex3f(-5,0.55,-1); glEnd(); // glPopMatrix(); // glPushMatrix(); // glTranslatef(0,0,0); // glutSolidSphere(0.10005,500,30); // glPopMatrix(); }

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