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• One Step-Ahead A-Star

  - by Jonathan Dickinson

  I am attempting to create a server-centric RTS (as opposed to usual parallel synchronised simulation route of most RTS games today) - however I am still leveraging the discreet N-turns-ahead paradigm discussed by one of the AOE developers on Gamasutra. I have [possibly questionably?] decided that the path finding should only ever find the next cell the entity needs to move to, and was wondering if anyone has any clever ideas on how to optimize the algorithm for this specific scenario - or any other ideas on how to keep the pathfinding as lean as possible on the server. I have investigated a few possible algorithms but could only come up with one appropriation: Tiered A-Star - Relatively large T1 tiles, work out (and cache) each cell as you enter it. Other than that: doing the full A-Star pass and caching the entire path, which might use too much memory if a large amount of units are present. I know about the existence of naive progressive pathfinding algorithms (if you hit a block, turn in the direction closer to your target etc.) but they suffer from infinite feedback loops - and very poor pathing even if visited blocks are memorised. Not an option. Many thanks.

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• Directional and orientation problem

  - by Ahmed Saleh

  I have drawn 5 tentacles which are shown in red. I have drew those tentacles on a 2D Circle, and positioned them on 5 vertices of the that circle. BTW, The circle is never be drawn, I have used it to simplify the problem. Now I wanted to attached that circle with tentacles underneath the jellyfish. There is a problem with the current code but I don't know what is it. You can see that the circle is parallel to the base of the jelly fish. I want it to be shifted so that it be inside the jelly fish. but I don't know how. I tried to multiply the direction vector to extend it but that didn't work. // One tentacle is constructed from nodes // Get the direction of the first tentacle's node 0 to node 39 of that tentacle; Vec3f dir = m_tentacle[0]->geNodesPos()[0] - m_tentacle[0]->geNodesPos()[39]; // Draw the circle with tentacles on it Vec3f pos = m_SpherePos; drawCircle(pos,dir,30,m_tentacle.size()); for (int i=0; i<m_tentacle.size(); i++) { m_tentacle[i]->Draw(); } // Draw the jelly fish, and orient it on the 2D Circle gl::pushMatrices(); Quatf q; // assign quaternion to rotate the jelly fish around the tentacles q.set(Vec3f(0,-1,0),Vec3f(dir.x,dir.y,dir.z)); // tanslate it to the position of the whole creature per every frame gl::translate(m_SpherePos.x,m_SpherePos.y,m_SpherePos.z); gl::rotate(q); // draw the jelly fish at center 0,0,0 drawHemiSphere(Vec3f(0,0,0),m_iRadius,90); gl::popMatrices();

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• Examples of good Javascript/HTML5 based games

  - by Zuch

  Now that Flash is largely being replaced with HTML5 elements (video, audio, canvas, etc.) are there any good examples of web-based games built on completely open standards (meaning Javascript, HTML and CSS)? I see a lot of examples of pure HTML5 implementations of what was once only in Flash (like stuff here: http://www.html5rocks.com/) but not many games, a domain which still seem dominated by Flash. I'm curious what's possible and what the limitations are.

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• Tile-wide extent tracing on a grid.

  - by Larolaro

  I'm currently working on A* pathfinding on a grid and I'm looking to smooth the generated path, while also considering the extent of the character moving along it. I'm using a grid for the pathfinding, however character movement is free roaming, not strict tile to tile movement. To achieve a smoother, more efficient path, I'm doing line traces on a grid to determine if there is unwalkable tiles between tiles to shave off unecessary corners. However, because a line trace is zero extent, it doesn't consider the extent of the character and gives bad results (not returning unwalkable tiles just missed by the line, causing unwanted collisions). So what I'm looking for is rather than a line algorithm that determines the tiles under it, I'm looking for one that determines the tiles under a tile-wide extent line. Here is an image to help visualise my problem! Does anyone have any ideas? I've been working with Bresenham's line and other alternatives but I haven't yet figured out how to nail this specific problem.

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• Change collision action

  - by PatrickR

  I have a collision detection and its working fine, the problem is, that whenever my "bird" is hitting a "cloud", the cloud dissapers and i get some points. The same happens for the "sol" which it should, but not with the clouds. How can this be changed ? ive tryed a lot, but can seem to figger it out. Collision Code - (void)update:(ccTime)dt { bird.position = ccpAdd(bird.position, skyVelocity); NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; for (CCSprite *bird in _projectiles) { bird.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(bird.position.x, bird.position.y, [bird boundingBox].size.width, [bird boundingBox].size.height); NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *cloudSprite in _targets) { cloudSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(cloudSprite.position.x, cloudSprite.position.y, [cloudSprite boundingBox].size.width, [cloudSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [cloudSprite boundingBox])) { [targetsToDelete addObject:cloudSprite]; } } for (CCSprite *solSprite in _targets) { solSprite.anchorPoint = ccp(0, 0); CGRect absoluteBox = CGRectMake(solSprite.position.x, solSprite.position.y, [solSprite boundingBox].size.width, [solSprite boundingBox].size.height); if (CGRectIntersectsRect([bird boundingBox], [solSprite boundingBox])) { [targetsToDelete addObject:solSprite]; score += 50/2; [scoreLabel setString:[NSString stringWithFormat:@"%d", score]]; } } // NÅR SKYEN BLIVER RAMT AF FUGLEN for (CCSprite *cloudSprite in targetsToDelete) { //[_targets removeObject:cloudSprite]; //[self removeChild:cloudSprite cleanup:YES]; } // NÅR SOLEN BLIVER RAMT AF FUGLEN for (CCSprite *solSprite in targetsToDelete) { [_targets removeObject:solSprite]; [self removeChild:solSprite cleanup:YES]; } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:bird]; } [targetsToDelete release]; } // NÅR FUGLEN BLIVER RAMT AF ALT ANDET for (CCSprite *bird in projectilesToDelete) { //[_projectiles removeObject:bird]; //[self removeChild:bird cleanup:YES]; } [projectilesToDelete release]; }

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• Trying to figure out SDL pixel manipulation?

  - by NoobScratcher

  Hello so I've found code that plots a pixel in an SDL Screen Surface : void putpixels(int x, int y, int color) { unsigned int *ptr = (unsigned int*)Screen->pixels; int lineoffset = y * (Screen->pitch / 4 ); ptr[lineoffset + x ] = color; } But I have no idea what its actually doing here this is my thoughts. You make an unsigned integer to hold the unsigned int version of pixels then you make another integer to hold the line offset and it equals to multiply by pitch which is then divided by 4 ... Now why am I dividing it by 4 and what is the pitch and why do I multiply it?? Why must I change the lineoffset and add it to the x value then equal it to colors? I'm soo confused.. ;/ I found this function here - http://sol.gfxile.net/gp/ch02.html

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• Dynamic libraries are not allowed on iOS but what about this?

  - by tapirath

  I'm currently using LuaJIT and its FFI interface to call C functions from LUA scripts. What FFI does is to look at dynamic libraries' exported symbols and let the developer use it directly form LUA. Kind of like Python ctypes. Obviously using dynamic libraries is not permitted in iOS for security reasons. So in order to come up with a solution I found the following snippet. /* (c) 2012 +++ Filip Stoklas, aka FipS, http://www.4FipS.com +++ THIS CODE IS FREE - LICENSED UNDER THE MIT LICENSE ARTICLE URL: http://forums.4fips.com/viewtopic.php?f=3&t=589 */ extern "C" { #include <lua.h> #include <lualib.h> #include <lauxlib.h> } // extern "C" #include <cassert> // Please note that despite the fact that we build this code as a regular // executable (exe), we still use __declspec(dllexport) to export // symbols. Without doing that FFI wouldn't be able to locate them! extern "C" __declspec(dllexport) void __cdecl hello_from_lua(const char *msg) { printf("A message from LUA: %s\n", msg); } const char *lua_code = "local ffi = require('ffi') \n" "ffi.cdef[[ \n" "const char * hello_from_lua(const char *); \n" // matches the C prototype "]] \n" "ffi.C.hello_from_lua('Hello from LUA!') \n" // do actual C call ; int main() { lua_State *lua = luaL_newstate(); assert(lua); luaL_openlibs(lua); const int status = luaL_dostring(lua, lua_code); if(status) printf("Couldn't execute LUA code: %s\n", lua_tostring(lua, -1)); lua_close(lua); return 0; } // output: // A message from LUA: Hello from LUA! Basically, instead of using a dynamic library, the symbols are exported directly inside the executable file. The question is: is this permitted by Apple? Thanks.

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• Why is chunk size often a power of two?

  - by danijar

  There are many Minecraft clones out there and I am working on my own implementation. A principle of terrain rendering is tiling the whole world in fixed size chunks to reduce the effort of localized changes. In Minecraft the chunk size is 16 x 16 x 256 as far as I now. And in clones I also always saw chunk sizes of a power of the number 2. Is there any reason for that, maybe performance or memory related? I know that powers of 2 play a special role in binary computers but what has that to do with the chunk size?

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• SRV from UAV on the same texture in directx

  - by notabene

  I'm programming gpgpu raymarching (volumetric raytracing) in directx11. I succesfully perform compute shader and save raymarched volume data to texture. Then i want to use same texture as SRV in normal graphic pipeline. But it doesnt work, texture is not visible. Texture is ok, when i save it file it is what i expect. Texture rendering is ok too, when i render another SRV, it is ok. So problem is only in UAV-SRV. I also triple checked if pointers are ok. Please help, i'm getting mad about this. Here is some code: //before dispatch D3D11_TEXTURE2D_DESC textureDesc; ZeroMemory( &textureDesc, sizeof( textureDesc ) ); textureDesc.Width = xr; textureDesc.Height = yr; textureDesc.MipLevels = 1; textureDesc.ArraySize = 1; textureDesc.SampleDesc.Count = 1; textureDesc.SampleDesc.Quality = 0; textureDesc.Usage = D3D11_USAGE_DEFAULT; textureDesc.BindFlags = D3D11_BIND_UNORDERED_ACCESS | D3D11_BIND_SHADER_RESOURCE ; textureDesc.Format = DXGI_FORMAT_R32G32B32A32_FLOAT; D3D->CreateTexture2D( &textureDesc, NULL, &pTexture ); D3D11_UNORDERED_ACCESS_VIEW_DESC viewDescUAV; ZeroMemory( &viewDescUAV, sizeof( viewDescUAV ) ); viewDescUAV.Format = DXGI_FORMAT_R32G32B32A32_FLOAT; viewDescUAV.ViewDimension = D3D11_UAV_DIMENSION_TEXTURE2D; viewDescUAV.Texture2D.MipSlice = 0; D3DD->CreateUnorderedAccessView( pTexture, &viewDescUAV, &pTextureUAV ); //the getSRV function after dispatch. D3D11_SHADER_RESOURCE_VIEW_DESC srvDesc ; ZeroMemory( &srvDesc, sizeof( srvDesc ) ); srvDesc.Format = DXGI_FORMAT_R32G32B32A32_FLOAT; srvDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D; srvDesc.Texture2D.MipLevels = 1; D3DD->CreateShaderResourceView( pTexture, &srvDesc, &pTextureSRV);

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• Which opcodes are faster at the CPU level?

  - by Geotarget

  In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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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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• Cocos2d update leaking memory

  - by Andrey Chernukha

  I have a weird issue - my app is leaking memory on device only, not on a simulator. It is leaking if i schedule update method anywhere, on any scene. It is leaking despite update method is empty, there's nothing inside it except NSLog. How can it be? I have even scheduled update on the very first scene where it seems there's nothing to leak, and scheduled another empty and it's leaking or not leaking but allocating something, the result is the same - the volume of the memory consumed is increasing and my app is crashing soon. I can detect the leakage via using Instruments-Memory-Activity Monitor or with help of following function: void report_memory(void) { struct task_basic_info info; mach_msg_type_number_t size = sizeof(info); kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size); if( kerr == KERN_SUCCESS ) { NSLog(@"Memory in use (in bytes): %u", info.resident_size); } else { NSLog(@"Error with task_info(): %s", mach_error_string(kerr)); } } Can anyone explain me what's going on?

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• backface culling error (in world space)

  - by acrilige

  I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation (is it correct?). (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason? For better explanation i upload picture with cube rotation screenshots: http://imageshack.us/photo/my-images/842/bcmove.png/ UPDATED: The error occurs only when triangle has non-zero offset from origin UPDATED 2: If i process backface culling in clip space (after transforming all vertices with view and projection matrix), and just check z coordinate of triangle normal - it works perfect... Can i perform culing RIGHT BEFORE view/proj transforms? In this case looks like culling will not depends of projection and it's not right?.. UPDATED 3: I found answer and will post it in two hours - again coz of reputation lack.

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• Lighting with VBO

  - by nkint

  I'm using a Java JOGL wrapper called processing.org. I have coded some enviroment on it and I'm quite proud of it even if it has some ready stuffs that I didn't know anything about it (==LIGHTS). Then, for some geometry, I've decided to use a VBO. I had to pass in the hard way and recode all lights. But I can't achieve the same result. This is the original light system: And this with VBO: With this code: Vec3D l; gl.glEnable(GL.GL_LIGHTING); gl.glEnable(GL.GL_LIGHT0); gl.glEnable(GL.GL_COLOR_MATERIAL); gl.glMaterialfv(GL.GL_FRONT_AND_BACK, GL.GL_AMBIENT, new float[]{0.8f,0f,0f}, 0); l = new Vec3D(0,0,-10); gl.glColor3f(0.8f,0f,0f); gl.glLightfv(GL.GL_LIGHT0, GL.GL_POSITION, new float[] { l.x, l.y, l.z, 0 }, 0); gl.glLightfv(GL.GL_LIGHT0, GL.GL_SPOT_DIRECTION, new float[] { 1, 1, 1, 1 }, 0); I can't achive the same light, the same color material, and the same wireframe stuffs. If needed I can also post the code I use for VBO, but it is quite standard vertex array grabbed on the net that uses glDrawArrays

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• How to calculate vertext normals for a mesh in Java in OpenGL ES application?

  - by alan mc

  Can some one point me to Java code ( in Java not C or C++) that calculates all the normals for all the vertices of a mesh for OpenGL ES application. I need this for lighting. Lets say I have a cube with following vertices and indices: float vertices[] = { -width, -height, -depth, // 0 width, -height, -depth, // 1 width, height, -depth, // 2 -width, height, -depth, // 3 -width, -height, depth, // 4 width, -height, depth, // 5 width, height, depth, // 6 -width, height, depth // 7 }; short indices[] = { 0, 2, 1, 0, 3, 2, 1,2,6, 6,5,1, 4,5,6, 6,7,4, 2,3,6, 6,3,7, 0,7,3, 0,4,7, 0,1,5, 0,5,4 }; In above specific example how many normals we need ?

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• In esenthel engine how can I remove some object from Gui class?

  - by Gajet

  I know many people in this site may not know esenthel engine at all and my question may be better answered at engine forum but I'm putting it here to share the name of a real easy to code gameengine with all of you: you can easily add a Button for example to your GUI class (gui is it's shared instance) with Gui += buttonInstance.create("click on me") but I'm just wondering how can you remove an on object from from Gui members. as far as I know there is no such a method as removeChild or getChildren or anything similar.

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• Playing part of a sfx audio file in HTML5 using WebAudio

  - by Matthew James Davis

  I have compiled all of my sound effects into one sequenced .ogg file. I have the start and stop times for each sound effect. How do I play the individual effects? That is, how do I play part of an audio file. More specificially, I've created a dictionary { 'sword_hit': { src: 'sfx.ogg', start: 265, // ms length: 212 // ms } } that my play_sound() function can use to look up 'sword_hit' and play the correct audio file at the correct start time for the correct duration. I simply need to know how to tell the WebAudio API to start playing at start ms and only play for length ms.

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• Why am I getting a return value of zero from my position computation function?

  - by Hussain Murtaza

  Ok I have a Function int x(), which is used in new Rectangle(x(),a,a,a); in DrawMethod in XNA but when I use it I get x() = 0 as as the answer.Here is my CODE: int x() { int px = (128 * 5); int xx = 0; for (int i = 0; i < 6; i++) { if (Mouse.GetState().X > px) { //xx = Mouse.GetState().X; xx = px; break; } else { px -= 128; } } return xx; } Here is the DrawMethod Code: if (set) { spriteBatch.Draw(texture, new Rectangle(x(), y(), texture.Width, texture.Height), Color.White); textpositionX = x(); textpositionY = y(); set = false; select = false; place = true; } else if(select) { spriteBatch.Draw(texture, new Rectangle(Mouse.GetState().X - texture.Width / 2, Mouse.GetState().Y-texture.Height / 2, texture.Width, texture.Height), Color.White); } else if (place) { spriteBatch.Draw(texture, new Rectangle(textpositionX, textpositionY, texture.Width, texture.Height), Color.White); select = false; set = false; }

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• Extrapolation breaks collision detection

  - by user22241

  Before applying extrapolation to my sprite's movement, my collision worked perfectly. However, after applying extrapolation to my sprite's movement (to smooth things out), the collision no longer works. This is how things worked before extrapolation: However, after I implement my extrapolation, the collision routine breaks. I am assuming this is because it is acting upon the new coordinate that has been produced by the extrapolation routine (which is situated in my render call ). After I apply my extrapolation How to correct this behaviour? I've tried puting an extra collision check just after extrapolation - this does seem to clear up a lot of the problems but I've ruled this out because putting logic into my rendering is out of the question. I've also tried making a copy of the spritesX position, extrapolating that and drawing using that rather than the original, thus leaving the original intact for the logic to pick up on - this seems a better option, but it still produces some weird effects when colliding with walls. I'm pretty sure this also isn't the correct way to deal with this. I've found a couple of similar questions on here but the answers haven't helped me. This is my extrapolation code: public void onDrawFrame(GL10 gl) { //Set/Re-set loop back to 0 to start counting again loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ SceneManager.getInstance().getCurrentScene().updateLogic(); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; tics++; } extrapolation = (float)(System.currentTimeMillis() + skipTicks - nextGameTick) / (float)skipTicks; render(extrapolation); } Applying extrapolation render(float extrapolation){ //This example shows extrapolation for X axis only. Y position (spriteScreenY is assumed to be valid) extrapolatedPosX = spriteGridX+(SpriteXVelocity*dt)*extrapolation; spriteScreenPosX = extrapolationPosX * screenWidth; drawSprite(spriteScreenX, spriteScreenY); } Edit As I mentioned above, I have tried making a copy of the sprite's coordinates specifically to draw with.... this has it's own problems. Firstly, regardless of the copying, when the sprite is moving, it's super-smooth, when it stops, it's wobbling slightly left/right - as it's still extrapolating it's position based on the time. Is this normal behavior and can we 'turn it off' when the sprite stops? I've tried having flags for left / right and only extrapolating if either of these is enabled. I've also tried copying the last and current positions to see if there is any difference. However, as far as collision goes, these don't help. If the user is pressing say, the right button and the sprite is moving right, when it hits a wall, if the user continues to hold the right button down, the sprite will keep animating to the right, while being stopped by the wall (therefore not actually moving), however because the right flag is still set and also because the collision routine is constantly moving the sprite out of the wall, it still appear to the code (not the player) that the sprite is still moving, and therefore extrapolation continues. So what the player would see, is the sprite 'static' (yes, it's animating, but it's not actually moving across the screen), and every now and then it shakes violently as the extrapolation attempts to do it's thing....... Hope this help

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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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• SDL2 with OpenGL -- weird results, what's wrong?

  - by ber4444

  I'm porting an app to iOS, and therefore need to upgrade it to SDL2 from SDL1.2 (so far I'm testing it as an on OS X desktop app only). However, when running the code with SDL2, I'm getting weird results as shown on the second image below (the first image is how it looks with SDL, correctly). The single changeset that causes this is this one, do you see something obviously wrong there, or does SDL2 have some OpenGL nuances I'm unaware of? My SDL is based on changeset dd7e57847ea9 from HG (since then there is one "Allow specifying of OpenGL 3.2 Core Profile on Mac OS X" commit, not sure if that would help).

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• Wrong faces culled in OpenGL when drawing a rectangular prism

  - by BadSniper

  I'm trying to learn opengl. I did some code for building a rectangular prism. I don't want to draw back faces so I used glCullFace(GL_BACK), glEnable(GL_CULL_FACE);. But I keep getting back faces also when viewing from front and also sometimes when rotating sides are vanishing. Can someone point me in right direction? glPolygonMode(GL_FRONT,GL_LINE); // draw wireframe polygons glColor3f(0,1,0); // set color green glCullFace(GL_BACK); // don't draw back faces glEnable(GL_CULL_FACE); // don't draw back faces glTranslatef(-10, 1, 0); // position glBegin(GL_QUADS); // face 1 glVertex3f(0,-1,0); glVertex3f(0,-1,2); glVertex3f(2,-1,2); glVertex3f(2,-1,0); // face 2 glVertex3f(2,-1,2); glVertex3f(2,-1,0); glVertex3f(2,5,0); glVertex3f(2,5,2); // face 3 glVertex3f(0,5,0); glVertex3f(0,5,2); glVertex3f(2,5,2); glVertex3f(2,5,0); // face 4 glVertex3f(0,-1,2); glVertex3f(2,-1,2); glVertex3f(2,5,2); glVertex3f(0,5,2); // face 5 glVertex3f(0,-1,2); glVertex3f(0,-1,0); glVertex3f(0,5,0); glVertex3f(0,5,2); // face 6 glVertex3f(0,-1,0); glVertex3f(2,-1,0); glVertex3f(2,5,0); glVertex3f(0,5,0); glEnd();

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• What is the practical use of IBOs / degenerate vertex in OpenGL?

  - by 0xFAIL

  Vertices in 3D models CAN get cut in the process of optimizing 3D geometry, (degenerate vertices) by 3D graphics software (Blender, ...) when exporting because they aren't needed when reusing a vertex for multiple triangles. (In the current case 3D data is exported from Blender as .ply and read by a simple application that displays the 3D model) Every vertex has a few attributes like position, color, normal, tangent,... But the data for each vertex that is cut through the vertex sharing is lost and is missing in the vertex shader. Modern shader techniques like Bump or Normal mapping require normals/tangents per vertex which are also cut. To use complex shader techniques IBOs must not be used? Or is there a way to use IBOs and retain the data per vertex that was origionally lost?

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• Rope Colliding with a Rectangle

  - by Colton

  I have my rope, and I have my rectangles. The rope is similar to the implementation found here: http://nehe.gamedev.net/tutorial/rope_physics/17006/ Now, I want to make the rope properly collide with the rectangle such that the rope will not pass through a rectangle, and wrap around the rectangle and all that good stuff. Currently, I have it set so no rope node can pass through a rect (successfully), however, this means a rope segment can still pass through a block. Ex: So the question is, what can I do to fix this? What I have tried: I create a rectangle between two nodes of a rope, calculate rotation between the nodes, and get myself a transformed rectangle. I can successfully detect a collision between rope segments and a (non-transformed) rectangle. Create a new node or pivot point around the corner of the block, and rearrange nodes to point to the corner node. Trouble is determining what corner the rope segment is passing through. And then the current rope setup goes wonky (based on verlet integration, so a sudden change in position causes the rope to wiggle like a seismograph during a magnitude 8 earth quake.) Among other issues that might be solvable, but its turning into a case by case thing, which doesn't seem right. I think the best answer here would just be a link to a tutorial (I simply can't find any, most lead to box2D or farseer, but I want to at least learn how it works before I hide behind an engine).

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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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