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• OpenGL 2D Rasterization Sub-Pixel Translations

  - by Armin Ronacher

  I have a tile based 2D engine where the projection matrix is an orthographic view of the world without any scaling applied. Thus: one pixel texture is drawn on the screen in the same size. That all works well and looks nice but if the camera makes a sub-pixel movement small lines appear between the tiles. I can tell you in advance what does not fix the problem: GL_NEAREST texture interpolation GL_CLAMP_TO_EDGE What does “fix” the problem is anchoring the camera to the nearest pixel instead of doing a sub-pixel translation. I can live with that, but the camera movement becomes jerky. Any ideas how to fix that problem without resorting to the rounding trick I do currently?

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• Why does my 3D model not translate the way I expect? [closed]

  - by ChocoMan

  In my first image, my model displays correctly: But when I move the model's position along the Z-axis (forward) I get this, yet the Y-axis doesnt change. An if I keep going, the model disappears into the ground: Any suggestions as to how I can get the model to translate properly visually? Here is how Im calling the model and the terrain in draw(): cameraPosition = new Vector3(camX, camY, camZ); // Copy any parent transforms. Matrix[] transforms = new Matrix[mShockwave.Bones.Count]; mShockwave.CopyAbsoluteBoneTransformsTo(transforms); Matrix[] ttransforms = new Matrix[terrain.Bones.Count]; terrain.CopyAbsoluteBoneTransformsTo(ttransforms); // Draw the model. A model can have multiple meshes, so loop. foreach (ModelMesh mesh in mShockwave.Meshes) { // This is where the mesh orientation is set, as well // as our camera and projection. foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.PreferPerPixelLighting = true; effect.World = transforms[mesh.ParentBone.Index] * Matrix.CreateRotationY(modelRotation) * Matrix.CreateTranslation(modelPosition); // Looking at the model (picture shouldnt change other than rotation) effect.View = Matrix.CreateLookAt(cameraPosition, modelPosition, Vector3.Up); effect.Projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f); effect.TextureEnabled = true; } // Draw the mesh, using the effects set above. prepare3d(); mesh.Draw(); } //Terrain test foreach (ModelMesh meshT in terrain.Meshes) { foreach (BasicEffect effect in meshT.Effects) { effect.EnableDefaultLighting(); effect.PreferPerPixelLighting = true; effect.World = ttransforms[meshT.ParentBone.Index] * Matrix.CreateRotationY(0) * Matrix.CreateTranslation(terrainPosition); // Looking at the model (picture shouldnt change other than rotation) effect.View = Matrix.CreateLookAt(cameraPosition, terrainPosition, Vector3.Up); effect.Projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f); effect.TextureEnabled = true; } // Draw the mesh, using the effects set above. prepare3d(); meshT.Draw(); DrawText(); } base.Draw(gameTime); } I'm suspecting that there may be something wrong with how I'm handling my camera. The model rotates fine on its Y-axis.

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• OpenGL textures trigger error 1281 if SFML is not called

  - by user3714670

  I am using SOIL to apply textures to VBOs, without textures i could change the background and display black (default color) vbos easily, but now with textures, openGL is giving an error 1281, the background is black and some textures are not applied. but the first texture IS applied (nothing else is working though). The strange thing is : if i create a dummy texture with SFML in the same program, all other textures do work. So i guess there is something i forgot in the texture creation/application, if someone could enlighten me. Here is the code i use to load textures, once loaded it is kept in memory, it mostly comes from the example of SOIL : texture = SOIL_load_OGL_single_cubemap( filename, SOIL_DDS_CUBEMAP_FACE_ORDER, SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_POWER_OF_TWO | SOIL_FLAG_MIPMAPS | SOIL_FLAG_DDS_LOAD_DIRECT ); if( texture > 0 ) { glEnable( GL_TEXTURE_CUBE_MAP ); glEnable( GL_TEXTURE_GEN_S ); glEnable( GL_TEXTURE_GEN_T ); glEnable( GL_TEXTURE_GEN_R ); glTexGeni( GL_S, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP ); glTexGeni( GL_T, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP ); glTexGeni( GL_R, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP ); glBindTexture( GL_TEXTURE_CUBE_MAP, texture ); std::cout << "the loaded single cube map ID was " << texture << std::endl; } else { std::cout << "Attempting to load as a HDR texture" << std::endl; texture = SOIL_load_OGL_HDR_texture( filename, SOIL_HDR_RGBdivA2, 0, SOIL_CREATE_NEW_ID, SOIL_FLAG_POWER_OF_TWO | SOIL_FLAG_MIPMAPS ); if( texture < 1 ) { std::cout << "Attempting to load as a simple 2D texture" << std::endl; texture = SOIL_load_OGL_texture( filename, SOIL_LOAD_AUTO, SOIL_CREATE_NEW_ID, SOIL_FLAG_POWER_OF_TWO | SOIL_FLAG_MIPMAPS | SOIL_FLAG_DDS_LOAD_DIRECT ); } if( texture > 0 ) { // enable texturing glEnable( GL_TEXTURE_2D ); // bind an OpenGL texture ID glBindTexture( GL_TEXTURE_2D, texture ); std::cout << "the loaded texture ID was " << texture << std::endl; } else { glDisable( GL_TEXTURE_2D ); std::cout << "Texture loading failed: '" << SOIL_last_result() << "'" << std::endl; } } and how i apply it when drawing : GLuint TextureID = glGetUniformLocation(shaderProgram, "myTextureSampler"); if(!TextureID) cout << "TextureID not found ..." << endl; // glEnableVertexAttribArray(TextureID); glActiveTexture(GL_TEXTURE0); if(SFML) sf::Texture::bind(sfml_texture); else { glBindTexture (GL_TEXTURE_2D, texture); // glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 1024, 768, 0, GL_RGB, GL_UNSIGNED_BYTE, &texture); } glUniform1i(TextureID, 0); I am not sure that SOIL is adapted to my program as i want something as simple as possible (i used sfml's texture object which was the best but i can't anymore), but if i can get it to work it would be great.

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• What are my tool options to prototype a 2D online multiplayer game?

  - by Asher Einhorn

  I'm looking for the best tool to allow me to quickly put together a 2D game that relies largely on networking. It's extremely likely that this game will require a server side program to constantly run. I have little experience with these things and since it's a prototype i'd like the easiest options for achieving this. I am looking to make this game for the web and mobile devices, although at present I only have access to ios hardware, (no android etc). I just want to get the bare bones of this set up so I can test it from the earliest opportunity to see if it's fun. EDIT - doesn't unity have some inbuilt networking stuff in it?

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• LWJGL - Mixing 2D and 3D

  - by nathan

  I'm trying to mix 2D and 3D using LWJGL. I have wrote 2D little method that allow me to easily switch between 2D and 3D. protected static void make2D() { glEnable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); glOrtho(0.0f, SCREEN_WIDTH, SCREEN_HEIGHT, 0.0f, 0.0f, 1.0f); GL11.glMatrixMode(GL11.GL_MODELVIEW); GL11.glLoadIdentity(); } protected static void make3D() { glDisable(GL_BLEND); GL11.glMatrixMode(GL11.GL_PROJECTION); GL11.glLoadIdentity(); // Reset The Projection Matrix GLU.gluPerspective(45.0f, ((float) SCREEN_WIDTH / (float) SCREEN_HEIGHT), 0.1f, 100.0f); // Calculate The Aspect Ratio Of The Window GL11.glMatrixMode(GL11.GL_MODELVIEW); glLoadIdentity(); } The in my rendering code i would do something like: make2D(); //draw 2D stuffs here make3D(); //draw 3D stuffs here What i'm trying to do is to draw a 3D shape (in my case a quad) and i 2D image. I found this example and i took the code from TextureLoader, Texture and Sprite to load and render a 2D image. Here is how i load the image. TextureLoader loader = new TextureLoader(); Sprite s = new Sprite(loader, "player.png") And how i render it: make2D(); s.draw(0, 0); It works great. Here is how i render my quad: glTranslatef(0.0f, 0.0f, 30.0f); glScalef(12.0f, 9.0f, 1.0f); DrawUtils.drawQuad(); Once again, no problem, the quad is properly rendered. DrawUtils is a simple class i wrote containing utility method to draw primitives shapes. Now my problem is when i want to mix both of the above, loading/rendering the 2D image, rendering the quad. When i try to load my 2D image with the following: s = new Sprite(loader, "player.png); My quad is not rendered anymore (i'm not even trying to render the 2D image at this point). Only the fact of creating the texture create the issue. After looking a bit at the code of Sprite and TextureLoader i found that the problem appears after the call of the glTexImage2d. In the TextureLoader class: glTexImage2D(target, 0, dstPixelFormat, get2Fold(bufferedImage.getWidth()), get2Fold(bufferedImage.getHeight()), 0, srcPixelFormat, GL_UNSIGNED_BYTE, textureBuffer); Commenting this like make the problem disappear. My question is then why? Is there anything special to do after calling this function to do 3D? Does this function alter the render part, the projection matrix?

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• Reacting to rectangle on rectangle collisions

  - by mcjohnalds45

  I don't know how to react to collisions between two axis aligned rectangles that have x, y, width and height values (x and y are from the centre of the box) to make them simply not overlap. I figured I'd just make them move away from each other depending on how far they intersect in the opposite direction (left, right, up or down) of where they collided. If I check for collisions only on the x axis or only on the y axis it works fine, but when checking for both collisions crazy stuff happens. This code executes when the first box collides with the second. It's in lua but feel free to answer in anything that isn't to too counter-intuitive. if box1.x < box2.x then box1.x = box1.x + box2.x - box1.x - (box1.width / 2) - (box2.width / 2) end if box1.x > box2.x then box1.x = box1.x - (box1.x - box2.x - (box1.width / 2) - (box2.width / 2)) end if box1.y < box2.y then box1.y = box1.y + box2.y - box1.y - (box1.height / 2) - (box2.height / 2) end if box1.y > box2.y then box1.y = box1.y - (box1.y - box2.y - (box1.height / 2) - (box2.height / 2)) end

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• How to implement soft edge areas with particles

  - by OpherV

  My game is created using Phaser, but the question itself is engine-agnostic. In my game I have several environments, essentially polygonal areas that player characters can move into and be affected by. For example ice, fire, poison etc' The graphic element of these areas is the color filled polygon area itself, and particles of the suitable type (in this example ice shards). This is how I'm currently implementing this - with a polygon mask covering a tilesprite with the particle pattern: The hard edge looks bad. I'd like to improve by doing two things: 1. Making the polygon fill area to have a soft edge, and blend into the background. 2. Have some of the shards go out of the polygon area, so that they are not cut in the middle and the area doesn't have a straight line for example (mockup): I think 1 can be achieved with blurring the polygon, but I'm not sure how to go about with 2. How would you go about implementing this?

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• Are there any good guides for making mods for Minecraft?

  - by Pureferret

  I've been coding in Java for 5 months at work now, and having past experience with programming in other languages, modifying existing code at Uni etc. I feel like I want to get started on (read: continue learning to program by) modding with minecraft. I know what I need, but not exactly how to do so. I once saw some good guides on the minecraft forum, but they all explained how to write in java, hows different classes in the code work etc. I'm more interested in how you decompile the code, write your own separate from the main 'trunk' of minecraft and then package it to install with a tool like 'Magic Loader'. My issue with these guides is that they always relied on being in windows, but I'm primarily a linux user, and the guides on the forums only seemed to assume you were on a Windows box. So is there a good 'walkthrough' for modding for Minecraft? Especially one where it assumes or at least allows for the fact you are in linux?

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• Managing constant buffers without FX interface

  - by xcrypt

  I am aware that there is a sample on working without FX in the samplebrowser, and I already checked that one. However, some questions arise: In the sample: D3DXMATRIXA16 mWorldViewProj; D3DXMATRIXA16 mWorld; D3DXMATRIXA16 mView; D3DXMATRIXA16 mProj; mWorld = g_World; mView = g_View; mProj = g_Projection; mWorldViewProj = mWorld * mView * mProj; VS_CONSTANT_BUFFER* pConstData; g_pConstantBuffer10->Map( D3D10_MAP_WRITE_DISCARD, NULL, ( void** )&pConstData ); pConstData->mWorldViewProj = mWorldViewProj; pConstData->fTime = fBoundedTime; g_pConstantBuffer10->Unmap(); They are copying their D3DXMATRIX'es to D3DXMATRIXA16. Checked on msdn, these new matrices are 16 byte aligned and optimised for intel pentium 4. So as my first question: 1) Is it necessary to copy matrices to D3DXMATRIXA16 before sending them to the constant buffer? And if no, why don't we just use D3DXMATRIXA16 all the time? I have another question about managing multiple constant buffers within one shader. Suppose that, within your shader, you have multiple constant buffers that need to be updated at different times: cbuffer cbNeverChanges { matrix View; }; cbuffer cbChangeOnResize { matrix Projection; }; cbuffer cbChangesEveryFrame { matrix World; float4 vMeshColor; }; Then how would I set these buffers all at different times? g_pd3dDevice->VSSetConstantBuffers( 0, 1, &g_pConstantBuffer10 ); gives me the possibility to set multiple buffers, but that is within one call. 2) Is that okay even if my constant buffers are updated at different times? And do I suppose I have to make sure the constantbuffers are in the same position in the array as the order they appear in the shader?

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• Bitmap Font Displays in Center Always Without Coding it Manually (Fix Coordinate Problem onText)

  - by David Dimalanta

  Is there a way on how to stay the texts in center without manually coding it or something, especially when making an update? I'm making a display for the highest score. Let's say that the score is 9. However, if the score is 9,999,999, the text displays still only at the fixed X and Y coordinate. Is there really a way to stay the text in center especially when there is changes when a player beats the new world record? Here's my code inside Sprite Batch: font.setScale(1.5f); font.draw(batch, "HIGHEST SCORE:", (900/10)*1 + 60, (1280/16)*10); font.draw(batch, "" + 9999999 + "", (900/10)*4, (1280/16)*8); batch.draw(grid_guide, 0, 0, 900, 1280); // --> For testing purpose only. // Where 9999999 is a new record score for example. Here's the image shown as example. I add it some red grid so that I could check if the display of score when updated will always display on center no matter how many digits takes place in. However, it is fixed, so I have to figure it out how to display it automatically on center regardless of the number of digits while updating for the new highscore. I have used the LibGDX preferences very well though to save and load records for the highscore.

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• Interpolating between two networked states?

  - by Vaughan Hilts

  I have many entities on the client side that are simulated (their velocities are added to their positions on a per frame basis) and I let them dead reckon themselves. They send updates about where they were last seen and their velocity changes. This works great and other players see this work find. However, after a while these players begin to desync after some time. This is because of latency. I'd like to know how I can interpolate between states so they appear to be in the correct position. I know where the player was LAST seen and their current velocity but interpolating to the last seen state causes the player to actually move -backwards-. I could not use velocity at all for other clients and simply 'lerp' them towards the appropriate direction but I feel this would cause jaggy movement. What are the alternatives?

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• Making body(box2d) a spite(andengine) in android

  - by Kadir

  I can't make body(box2d) a spite(andengine) and at the same time i wanna apply MoveModifier to sprite which is body.if i can make just body,it works namely the srites can collide.if i can apply just MoveModifier to sprites,the sprites can move where i want.but i wanna make body(they can collide) and apply MoveModifier(they can move where i want) at the same time.How can i do? this my code just run MoveModifier not as body at the same time. circles[i] = new Sprite(startX, startY, textRegCircle[i]); body[i] = PhysicsFactory.createCircleBody(physicsWorld, circles[i], BodyType.DynamicBody, FIXTURE_DEF); physicsWorld.registerPhysicsConnector(new PhysicsConnector(circles[i], body[i], true, true)); circles[i].registerEntityModifier( (IEntityModifier) new SequenceEntityModifier ( new MoveModifier(10.0f, circles[i].getX(), circles[i].getX(), circles[i].getY(),CAMERA_HEIGHT+64.0f))); scene.getLastChild().attachChild(circles[i]); scene.registerUpdateHandler(physicsWorld);

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• Maya Animated Character export for XNA 4.0 problem

  - by FahidK

  To begin with, I'm trying to export an animated character in .fbx format from Maya 2013 to XNA 4.0 In Maya, The Model has a basic rig and the animations are in clips made in the Trax editor. so the issue i'm having is after selecting the model and the root joint and then hitting export in .fbx format, for some reason when i open the exported .fbx file the joint system is detached from the model with no animation. Btw, i have the animations in clips so that they can be called in code, for example "run","walk","attack". So, what can i do to solve this problem? Thank you.

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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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• Generated 3d tree meshes

  - by Jari Komppa

  I did not find a question on these lines yet, correct me if I'm wrong. Trees (and fauna in general) are common in games. Due to their nature, they are a good candidate for procedural generation. There's SpeedTree, of course, if you can afford it; as far as I can tell, it doesn't provide the possibility of generating your tree meshes at runtime. Then there's SnappyTree, an online webgl based tree generator based on the proctree.js which is some ~500 lines of javascript. One could use either of above (or some other tree generator I haven't stumbled upon) to create a few dozen tree meshes beforehand - or model them from scratch in a 3d modeller - and then randomly mirror/scale them for a few more variants.. But I'd rather have a free, linkable tree mesh generator. Possible solutions: Port proctree.js to c++ and deal with the open source license (doesn't seem to be gpl, so could be doable; the author may also be willing to co-operate to make the license even more free). Roll my own based on L-systems. Don't bother, just use offline generated trees. Use some other method I haven't found yet.

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• How to cover the widest range of computers when publishing?

  - by DevilWithin

  When you plan a game, or even when you already made a game, and its time to publish, you wonder how much of your audience is covered by the game technology demands. I'm directing this essentialy to casual games, as I constantly see people having old laptops and being unable to replace them. Laptops with integrated cards whose OpenGL version doesn't even support textures larger than 1024x1024. These people may be avid gamers as well, and a reasonable share of the audience to consider giving them the chance to play casual games, once they cannot play any blockbusters. As I've seen happening, a very "noticeable" example is Angry Birds. It's gameplay is merely casual (I think nobody disagrees here) and still, it uses so high resolution textures that at least OpenGL 2.0 or around is needed, which blocks away a lot of people. So, the actual question is: what is a good tradeoff for this issue? Would it be better to just sacrifice the texture resolution for everyone, but have more supported hardware? Would it be better to keep the high quality and just slice the textures into smaller ones, sacrificing the performance a little bit? What else? Any ideas about this topic are welcome for discussion.

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• FBX Importer - Texture Name

  - by CmasterG

  I have a problem with the FBX SDK. I read in the data for the vertex position and the uv coordinates. It works fine, but now I want to read for each polygon to which texture it belongs, so that I can have models with multiple textures. Can anyone tell me how I can get the texture name (file name) for my polygon. My code to read in vertex position and uv coordinates is the following: int i, j, lPolygonCount = pMesh->GetPolygonCount(); FbxVector4* lControlPoints = pMesh->GetControlPoints(); int vertexId = 0; for (i = 0; i < lPolygonCount; i++) { int lPolygonSize = pMesh->GetPolygonSize(i); for (j = 0; j < lPolygonSize; j++) { int lControlPointIndex = pMesh->GetPolygonVertex(i, j); FbxVector4 pos = lControlPoints[lControlPointIndex]; current_model[vertex_index].x = pos.mData[0] - pivot_offset[0]; current_model[vertex_index].y = pos.mData[1] - pivot_offset[1]; current_model[vertex_index].z = pos.mData[2]- pivot_offset[2]; FbxVector4 vertex_normal; pMesh->GetPolygonVertexNormal(i,j, vertex_normal); current_model[vertex_index].nx = vertex_normal.mData[0]; current_model[vertex_index].ny = vertex_normal.mData[1]; current_model[vertex_index].nz = vertex_normal.mData[2]; //read in UV data FbxStringList lUVSetNameList; pMesh->GetUVSetNames(lUVSetNameList); //get lUVSetIndex-th uv set const char* lUVSetName = lUVSetNameList.GetStringAt(0); const FbxGeometryElementUV* lUVElement = pMesh->GetElementUV(lUVSetName); if(!lUVElement) continue; // only support mapping mode eByPolygonVertex and eByControlPoint if( lUVElement->GetMappingMode() != FbxGeometryElement::eByPolygonVertex && lUVElement->GetMappingMode() != FbxGeometryElement::eByControlPoint ) return; //index array, where holds the index referenced to the uv data const bool lUseIndex = lUVElement->GetReferenceMode() != FbxGeometryElement::eDirect; const int lIndexCount= (lUseIndex) ? lUVElement->GetIndexArray().GetCount() : 0; FbxVector2 lUVValue; //get the index of the current vertex in control points array int lPolyVertIndex = pMesh->GetPolygonVertex(i,j); //the UV index depends on the reference mode //int lUVIndex = lUseIndex ? lUVElement->GetIndexArray().GetAt(lPolyVertIndex) : lPolyVertIndex; int lUVIndex = pMesh->GetTextureUVIndex(i, j); lUVValue = lUVElement->GetDirectArray().GetAt(lUVIndex); current_model[vertex_index].tu = (float)lUVValue.mData[0]; current_model[vertex_index].tv = (float)lUVValue.mData[1]; vertex_index ++; } } float v1[3], v2[3], v3[3]; v1[0] = current_model[vertex_index - 3].x; v1[1] = current_model[vertex_index - 3].y; v1[2] = current_model[vertex_index - 3].z; v2[0] = current_model[vertex_index - 2].x; v2[1] = current_model[vertex_index - 2].y; v2[2] = current_model[vertex_index - 2].z; v3[0] = current_model[vertex_index - 1].x; v3[1] = current_model[vertex_index - 1].y; v3[2] = current_model[vertex_index - 1].z; collision_model->addTriangle(v1,v2,v3);

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• Implementing Circle Physics in Java

  - by Shijima

  I am working on a simple physics based game where 2 balls bounce off each other. I am following a tutorial, 2-Dimensional Elastic Collisions Without Trigonometry, for the collision reactions. I am using Vector2 from the LIBGDX library to handle vectors. I am a bit confused on how to implement step 6 in Java from the tutorial. Below is my current code, please note that the code strictly follows the tutorial and there are redundant pieces of code which I plan to refactor later. Note: refrences to this refer to ball 1, and ball refers to ball 2. /* * Step 1 * * Find the Normal, Unit Normal and Unit Tangential vectors */ Vector2 n = new Vector2(this.position[0] - ball.position[0], this.position[1] - ball.position[1]); Vector2 un = n.normalize(); Vector2 ut = new Vector2(-un.y, un.x); /* * Step 2 * * Create the initial (before collision) velocity vectors */ Vector2 v1 = this.velocity; Vector2 v2 = ball.velocity; /* * Step 3 * * Resolve the velocity vectors into normal and tangential components */ float v1n = un.dot(v1); float v1t = ut.dot(v1); float v2n = un.dot(v2); float v2t = ut.dot(v2); /* * Step 4 * * Find the new tangential Velocities after collision */ float v1tPrime = v1t; float v2tPrime = v2t; /* * Step 5 * * Find the new normal velocities */ float v1nPrime = v1n * (this.mass - ball.mass) + (2 * ball.mass * v2n) / (this.mass + ball.mass); float v2nPrime = v2n * (ball.mass - this.mass) + (2 * this.mass * v1n) / (this.mass + ball.mass); /* * Step 6 * * Convert the scalar normal and tangential velocities into vectors??? */

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• collision detection problems - Javascript/canvas game

  - by Tom Burman

  Ok here is a more detailed version of my question. What i want to do: i simply want the have a 2d array to represent my game map. i want a player sprite and i want that sprite to be able to move around my map freely using the keyboard and also have collisions with certain tiles of my map array. i want to use very large maps so i need a viewport. What i have: I have a loop to load the tile images into an array: /Loop to load tile images into an array var mapTiles = []; for (x = 0; x <= 256; x++) { var imageObj = new Image(); // new instance for each image imageObj.src = "images/prototype/"+x+".jpg"; mapTiles.push(imageObj); } I have a 2d array for my game map: //Array to hold map data var board = [ [1,2,3,4,3,4,3,4,5,6,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [17,18,19,20,19,20,19,20,21,22,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [33,34,35,36,35,36,35,36,37,38,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [49,50,51,52,51,52,51,52,53,54,1,1,1,1,1,1,1,1,1,1,1,1,1,197,198,199,1,1,1,1], [65,66,67,68,146,147,67,68,69,70,1,1,1,1,1,1,1,1,216,217,1,1,1,213,214,215,1,1,1,1], [81,82,83,161,162,163,164,84,85,86,1,1,1,1,1,1,1,1,232,233,1,1,1,229,230,231,1,1,1,1], [97,98,99,177,178,179,180,100,101,102,1,1,1,1,59,1,1,1,248,249,1,1,1,245,246,247,1,1,1,1], [1,1,238,1,1,1,1,239,240,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [216,217,254,1,1,1,1,255,256,1,204,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [232,233,1,1,1,117,118,1,1,1,220,1,1,119,120,1,1,1,1,1,1,1,1,1,1,1,119,120,1,1], [248,249,1,1,1,133,134,1,1,1,1,1,1,135,136,1,1,1,1,1,1,59,1,1,1,1,135,136,1,1], [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,216,217,1,1,1,1,1,1,60,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,232,233,1,1,1,1,1,1,1,1,1,1,1,1,1,1,204,1,1,1,1,1,1,1,1,1,1,1], [1,1,248,249,1,1,1,1,1,1,1,1,1,1,1,1,1,1,220,1,1,1,1,1,1,216,217,1,1,1], [1,1,1,1,1,1,1,1,1,1,1,1,149,150,151,1,1,1,1,1,1,1,1,1,1,232,233,1,1,1], [12,12,12,12,12,12,12,13,1,1,1,1,165,166,167,1,1,1,1,1,1,119,120,1,1,248,249,1,1,1], [28,28,28,28,28,28,28,29,1,1,1,1,181,182,183,1,1,1,1,1,1,135,136,1,1,1,1,1,1,1], [44,44,44,44,44,15,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,59,1,1,197,198,199,1,1,1,1,119,120,1], [1,1,1,1,1,27,28,29,1,1,216,217,1,1,1,1,1,1,1,1,213,214,215,1,1,1,1,135,136,1], [1,1,1,1,1,27,28,29,1,1,232,233,1,1,1,1,1,1,1,1,229,230,231,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,248,249,1,1,1,1,1,1,1,1,245,246,247,1,1,1,1,1,1,1], [1,1,1,197,198,199,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,213,214,215,28,29,1,1,1,1,1,60,1,1,1,1,204,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,229,230,231,28,29,1,1,1,1,1,1,1,1,1,1,220,1,1,1,1,119,120,1,1,1,1,1], [1,1,1,245,246,247,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,135,136,1,1,60,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1], [1,1,1,1,1,27,28,29,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1] ]; I have my loop to place the correct tile sin the correct positions: //Loop to place tiles onto screen in correct position for (x = 0; x <= viewWidth; x++){ for (y = 0; y <= viewHeight; y++){ var width = 32; var height = 32; context.drawImage(mapTiles[board[y+viewY][x+viewX]],x*width, y*height); } } I Have my player object : //Place player object context.drawImage(playerImg, (playerX-viewX)*32,(playerY-viewY)*32, 32, 32); I have my viewport setup: //Set viewport pos viewX = playerX - Math.floor(0.5 * viewWidth); if (viewX < 0) viewX = 0; if (viewX+viewWidth > worldWidth) viewX = worldWidth - viewWidth; viewY = playerY - Math.floor(0.5 * viewHeight); if (viewY < 0) viewY = 0; if (viewY+viewHeight > worldHeight) viewY = worldHeight - viewHeight; I have my player movement: canvas.addEventListener('keydown', function(e) { console.log(e); var key = null; switch (e.which) { case 37: // Left if (playerY > 0) playerY--; break; case 38: // Up if (playerX > 0) playerX--; break; case 39: // Right if (playerY < worldWidth) playerY++; break; case 40: // Down if (playerX < worldHeight) playerX++; break; } My Problem: I have my map loading an it looks fine, but my player position thinks it's on a different tile to what it actually is. So for instance, i know that if my player moves left 1 tile, the value of that tile should be 2, but if i print out the value it should be moving to (2), it comes up with a different value. How ive tried to solve the problem: I have tried swap X and Y values for the initialization of my player, for when my map prints. If i swap the x and y values in this part of my code: context.drawImage(mapTiles[board[y+viewY][x+viewX]],x*width, y*height); The map doesnt get draw correctly at all and tiles are placed all in random positions or orientations IF i sway the x and y values for my player in this line : context.drawImage(playerImg, (playerX-viewX)*32,(playerY-viewY)*32, 32, 32); The players movements are inversed, so up and down keys move my player left and right viceversa. My question: Where am i going wrong in my code, and how do i solve it so i have my map looking like it should and my player moving as it should as well as my player returning the correct tileID it is standing on or moving too. Thanks Again ALSO Here is a link to my whole code: prototype

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• Java: Reflection Packet Builder using getField()

  - by Matchlighter

  So I just finished writing a packet builder that dynamically loads data into a data stream which is then sent out. Each builder operates by finding fields in its class (and its superclasses) that are marked with an @data annotation. Upon finishing the builder, I remembered that getFields() does not return in "any specific order". I quite like my builder because it allows for quite simple, yet hard-typed packets. Could this implementation be a problem? What would be the best next step to keep the simplicity - do alphabetical sorting of fields?

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• Automatically triggering standard spaceship controls to stop its motion

  - by Garan

  I have been working on a 2D top-down space strategy/shooting game. Right now it is only in the prototyping stage (I have gotten basic movement) but now I am trying to write a function that will stop the ship based on it's velocity. This is being written in Lua, using the Love2D engine. My code is as follows (note- object.dx is the x-velocity, object.dy is the y-velocity, object.acc is the acceleration, and object.r is the rotation in radians): function stopMoving(object, dt) local targetr = math.atan2(object.dy, object.dx) if targetr == object.r + math.pi then local currentspeed = math.sqrt(object.dx*object.dx+object.dy*object.dy) if currentspeed ~= 0 then object.dx = object.dx + object.acc*dt*math.cos(object.r) object.dy = object.dy + object.acc*dt*math.sin(object.r) end else if (targetr - object.r) >= math.pi then object.r = object.r - object.turnspeed*dt else object.r = object.r + object.turnspeed*dt end end end It is implemented in the update function as: if love.keyboard.isDown("backspace") then stopMoving(player, dt) end The problem is that when I am holding down backspace, it spins the player clockwise (though I am trying to have it go the direction that would be the most efficient at getting to the angle it would have to be) and then it never starts to accelerate the player in the direction opposite to it's velocity. What should I change in this code to get that to work? EDIT : I'm not trying to just stop the player in place, I'm trying to get it to use it's normal commands to neutralize it's existing velocity. I also changed math.atan to math.atan2, apparently it's better. I noticed no difference when running it, though.

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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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• How to properly do weapon cool-down reload timer in multi-player laggy environment?

  - by John Murdoch

  I want to handle weapon cool-down timers in a fair and predictable way on both client on server. Situation: Multiple clients connected to server, which is doing hit detection / physics Clients have different latency for their connections to server ranging from 50ms to 500ms. They want to shoot weapons with fairly long reload/cool-down times (assume exactly 10 seconds) It is important that they get to shoot these weapons close to the cool-down time, as if some clients manage to shoot sooner than others (either because they are "early" or the others are "late") they gain a significant advantage. I need to show time remaining for reload on player's screen Clients can have clocks which are flat-out wrong (bad timezones, etc.) What I'm currently doing to deal with latency: Client collects server side state in a history, tagged with server timestamps Client assesses his time difference with server time: behindServerTimeNs = (behindServerTimeNs + (System.nanoTime() - receivedState.getServerTimeNs())) / 2 Client renders all state received from server 200 ms behind from his current time, adjusted by what he believes his time difference with server time is (whether due to wrong clocks, or lag). If he has server states on both sides of that calculated time, he (mostly LERP) interpolates between them, if not then he (LERP) extrapolates. No other client-side prediction of movement, e.g., to make his vehicle seem more responsive is done so far, but maybe will be added later So how do I properly add weapon reload timers? My first idea would be for the server to send each player the time when his reload will be done with each world state update, the client then adjusts it for the clock difference and thus can estimate when the reload will be finished in client-time (perhaps considering also for latency that the shoot message from client to server will take as well?), and if the user mashes the "shoot" button after (or perhaps even slightly before?) that time, send the shoot event. The server would get the shoot event and consider the time shot was made as the server time when it was received. It would then discard it if it is nowhere near reload time, execute it immediately if it is past reload time, and hold it for a few physics cycles until reload is done in case if it was received a bit early. It does all seem a bit convoluted, and I'm wondering whether it will work (e.g., whether it won't be the case that players with lower ping get better reload rates), and whether there are more elegant solutions to this problem.

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• Checking for alternate keys with XNA IsKeyDown

  - by jocull

  I'm working on picking up XNA and this was a confusing point for me. KeyboardState keyState = Keyboard.GetState(); if (keyState.IsKeyDown(Keys.Left) || keyState.IsKeyDown(Keys.A)) { //Do stuff... } The book I'm using (Learning XNA 4.0, O'Rielly) says that this method accepts a bitwise OR series of keys, which I think should look like this... KeyboardState keyState = Keyboard.GetState(); if (keyState.IsKeyDown(Keys.Left | Keys.A)) { //Do stuff... } But I can't get it work. I also tried using !IsKeyUp(... | ...) as it said that all keys had to be down for it to be true, but had no luck with that either. Ideas? Thanks.

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• Moving objects colliding when using unalligned collision avoidance (steering)

  - by James Bedford

  I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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