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2D XNA C#: Texture2D Wrapping Issue

- by Kieran

Working in C#/XNA for a Windows game: I'm using Texture2D to draw sprites. All of my sprites are 16 x 32. The sprites move around the screen as you would expect, by changing the top X/Y position of them when they're being drawn by the spritebatch. Most of the time when I run the game, the sprites appear like this: and when moved, they move as I expect, as one element. Infrequently they appear like this: and when moved it's like there are two sprites with a gap in between them - it's hard to describe. It only seems to happen sometimes - is there something I'm missing? I'd really like to know why this is happening. [Edit:] Adding Draw code as requested: This is the main draw routine - it first draws the sprite to a RenderTarget then blows it up by a scale of 4: protected override void Draw(GameTime gameTime) { // Draw to render target GraphicsDevice.SetRenderTarget(renderTarget); GraphicsDevice.Clear(Color.CornflowerBlue); Texture2D imSprite = null; spriteBatch.Begin(SpriteSortMode.FrontToBack, null, SamplerState.PointWrap, null, null); ManSprite.Draw(spriteBatch); base.Draw(gameTime); spriteBatch.End(); // Draw render target to screen GraphicsDevice.SetRenderTarget(null); imageFrame = (Texture2D)renderTarget; GraphicsDevice.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.DarkSlateBlue, 1.0f, 0); spriteBatch.Begin(SpriteSortMode.FrontToBack, null, SamplerState.PointClamp, null, null); spriteBatch.Draw(imageFrame, new Vector2(0, 0), null, Color.White, 0, new Vector2(0, 0), IM_SCALE, SpriteEffects.None, 0); spriteBatch.End(); } This is the draw routine for the Sprite class: public virtual void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(Texture, new Vector2(PositionX, PositionY), null, Color.White, 0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0.3f); }

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matrix 4x4 position data

- by freefallr

I understand that a 4x4 matrix holds rotation and position data. The rotation data is held in the 3x3 sub-matrix at the top left of the matrix. The position data is held in the last column of the matrix. e.g. glm::vec3 vParentPos( mParent[3][0], mParent[3][1], mParent[3][2] ); My question is - am I accessing the parent matrix correctly in the example above? I know that opengl uses a different matrix ordering that directx, (row order instead of column order or something), so, should the mParent be accessed as follows instead? glm::vec3 vParentPos( mParent[0][3], mParent[1][3], mParent[2][3] ); thanks!

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Finding Z given X & Y coordinates on terrain?

- by mrky

I need to know what the most efficient way of finding Z given X & Y coordinates on terrain. My terrain is set up as a grid, each grid block consisting of two triangles, which may be flipped in any direction. I want to move game objects smoothly along the floor of the terrain without "stepping." I'm currently using the following method with unexpected results: double mapClass::getZ(double x, double y) { int vertexIndex = ((floor(y))*width*2)+((floor(x))*2); vec3ray ray = {glm::vec3(x, y, 2), glm::vec3(x, y, 0)}; vec3triangle tri1 = { glmFrom(vertices[vertexIndex].v1), glmFrom(vertices[vertexIndex].v2), glmFrom(vertices[vertexIndex].v3) }; vec3triangle tri2 = { glmFrom(vertices[vertexIndex+1].v1), glmFrom(vertices[vertexIndex+1].v2), glmFrom(vertices[vertexIndex+1].v3) }; glm::vec3 intersect; if (!intersectRayTriangle(tri1, ray, intersect)) { intersectRayTriangle(tri2, ray, intersect); } return intersect.z; } intersectRayTriangle() and glmFrom() are as follows: bool intersectRayTriangle(vec3triangle tri, vec3ray ray, glm::vec3 &worldIntersect) { glm::vec3 barycentricIntersect; if (glm::intersectLineTriangle(ray.origin, ray.direction, tri.p0, tri.p1, tri.p2, barycentricIntersect)) { // Convert barycentric to world coordinates double u, v, w; u = barycentricIntersect.x; v = barycentricIntersect.y; w = 1 - (u+v); worldIntersect.x = (u * tri.p0.x + v * tri.p1.x + w * tri.p2.x); worldIntersect.y = (u * tri.p0.y + v * tri.p1.y + w * tri.p2.y); worldIntersect.z = (u * tri.p0.z + v * tri.p1.z + w * tri.p2.z); return true; } else { return false; } } glm::vec3 glmFrom(s_point3f point) { return glm::vec3(point.x, point.y, point.z); } My convenience structures are defined as: struct s_point3f { GLfloat x, y, z; }; struct s_triangle3f { s_point3f v1, v2, v3; }; struct vec3ray { glm::vec3 origin, direction; }; struct vec3triangle { glm::vec3 p0, p1, p2; }; vertices is defined as: std::vector<s_triangle3f> vertices; Basically, I'm trying to get the intersect of a ray (which is positioned at the x, and y coordinates specified facing pointing downwards toward the terrain) and one of the two triangles on the grid. getZ() rarely returns anything but 0. Other times, the numbers it generates seem to be completely off. Am I taking the wrong approach? Can anyone see a problem with my code? Any help or critique is appreciated!

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OpenGL Tessellation makes point

- by urza57

A little problem with my tessellation shader. I try to implement a simple tessellation shader but it only makes points. Here's my vertex shader : out vec4 ecPosition; out vec3 ecNormal; void main( void ) { vec4 position = gl_Vertex; gl_Position = gl_ModelViewProjectionMatrix * position; ecPosition = gl_ModelViewMatrix * position; ecNormal = normalize(gl_NormalMatrix * gl_Normal); } My tessellation control shader : layout(vertices = 3) out; out vec4 ecPosition3[]; in vec3 ecNormal[]; in vec4 ecPosition[]; out vec3 myNormal[]; void main() { gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position; myNormal[gl_InvocationID] = ecNormal[gl_InvocationID]; ecPosition3[gl_InvocationID] = ecPosition[gl_InvocationID]; gl_TessLevelOuter[0] = float(4.0); gl_TessLevelOuter[1] = float(4.0); gl_TessLevelOuter[2] = float(4.0); gl_TessLevelInner[0] = float(4.0); } And my Tessellation Evaluation shader: layout(triangles, equal_spacing, ccw) in; in vec3 myNormal[]; in vec4 ecPosition3[]; out vec3 ecNormal; out vec4 ecPosition; void main() { float u = gl_TessCoord.x; float v = gl_TessCoord.y; float w = gl_TessCoord.z; vec3 position = vec4(gl_in[0].gl_Position.xyz * u + gl_in[1].gl_Position.xyz * v + gl_in[2].gl_Position.xyz * w ); vec3 position2 = vec4(ecPosition3[0].xyz * u + ecPosition3[1].xyz * v + ecPosition3[2].xyz * w ); vec3 normal = myNormal[0] * u + myNormal[1] * v + myNormal[2] * w ); ecNormal = normal; gl_Position = vec4(position, 1.0); ecPosition = vec4(position2, 1.0); } Thank you !

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HLSL - Creating Shadows in 2D

- by richard

The way that I create shadows is by the following technique: http://www.catalinzima.com/2010/07/my-technique-for-the-shader-based-dynamic-2d-shadows/ But I have questions to HLSL. The way that I currently do it is, I have a black and white image, where Black means 'object', and white means 'nothing'. I then distort the image like in the tutorial. I do this with a pixel shader, but instead of rendering to the screen, I render to a texture, back to my application. I then take this, and create the shadows, and then send it back to the graphics card to undo the distortion, after the shadow has been added - this comes back and I have a stencil of shadow. I can put this ontop of the original image and send them back to the graphics card, which then puts them on the screen. To me this is alot of back and forth. Is there a way i can avoid this? The problem that I am having is that I need to basically go through all positions in the texture 3 times, and use the new new texture every time instead of the orginal one. I tried to read up on Passes, but i don't think that i am heading in the right direction there. Help?

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Why does Unity3D crash in VirtualBox?

- by FakeRainBrigand

I'm running Unity3D in a virtual instance of Windows, using the Virtual Box software on Linux. I have guest additions installed with DirectX support. I've tried using Windows XP SP3 32-bit, and Windows 7 64bit. My host is Ubuntu 12.04 64bit. I installed and registered Unity on both. It loads up fine, and then crashes my entire VirtualBox instance (equivalent of a computer shutting off with no warning).

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What is the best way to "carve" a terrain created from a heightmap?

- by tigrou

I have a 3d landscape created from a heightmap. I'd like to "carve" some holes in that terrain. That will allow me to create bridges, caverns and tunnels inside it. That operation will be done in the game editor so it doesn't need to be realtime. In the end, rendering is done using traditional polygons. What would be the best/easiest way to do that ? I already think about several solutions : Solution 1 1) Create voxels from the heightmap (very easy). In other words, fill a 3D array like this : voxels[32][32][32] from the heightmap values. 2) Carve holes in the voxels as i want (easy too). 3) Convert voxels to polygons using some iso-surface extraction technique (like marching cubes). 4) Reduce (decimate) polygons created in 3). This technique seems to be the most promising for giving good results (untested). However the problem with marching cubes is that they tends to produce lots of polygons thus reducing them is mandatory. Implementing 4) also seems not trivial, i have read several papers on the web and it seems pretty complex. I was also unable to find an example, code snippet or something to start writing an algorithm for triangle mesh decimation. Maybe there is a special decimation algorithm (simpler) for meshes created from marching cubes ? Solution 2 1) Create some triangle mesh from the heighmap (easy). 2) Apply severals 3D boolean operation (eg: subtraction with a sphere) to carve the mesh. 3) apply some procedure to reduce polygons (optional). Operation 2) seems to be very complex and to be honest i have no idea how to do that. Also applying many boolean operation seems to be slow and will maybe degrade the triangle mesh every time a boolean operation is applied.

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Double sides face with two normals

- by Marnix

I think this isn't possible, but I just want to check this: Is it possible to create a face in opengl that has two normals? So: I want the inside and outside of some cilinder to be drawn, but I want the lights to do as expected and not calculate it for the normal given. I was trying to do this with backface culling off, so I would have both faces, but the light was wrongly calculated of course. Is this possible, or do I have to draw an inside and an outside? So draw twice?

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Deserialize inherited classes into the same list in XNA

- by M0rgenstern

I am writing a Gui for a game (for what else ...). Therefor I wrote a class GuiElement which has some serializeable fields. From this class I deflect a Class "Button" which has one serializeable field more. Furthermore, I have a Class GuiWindow, which is as well deflected from "GuiElement". An Object of this Class has a Field "HandledElements" of the type "List". To know the layout of the Menues, I use XML-Files, which look like that (for example): <?xml version="1.0" encoding="utf-8" ?> <XnaContent xmlns:Generic="System.Collections.Generic"> <Asset Type="System.Collections.Generic.List[GUI.GuiWindow]"> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>MainMenu</Name> <HandledElements> <Item> <Position>100 100</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>Optionen</Name> <Caption>Optionen</Caption> </Item> </HandledElements> </Item> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>false</IsActive> <Name>Options</Name> <HandledElements> </HandledElements> </Item> </Asset> </XnaContent> As you can see, the first window has in its "HandledElements" List an Item with the Field . This is a field which only a Button has. The Problem is now: I can't deserialize this XML file, because GuiElement does not have this Field, it only has the few fields above. I thought it would know automatically which Class to use,but it doesn't. Do I really have to give my windows a list for each child class of GuiElement? Or can I do another workaround?

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Objective C - Aggro with Images

- by Will

I have three UIImageViews. enemy1, enemy1AggroBox and mainSprite. What I want to do is when mainSprite and enemy1AggroBox interect, I want enemy1 to start moving towards mainSprite. Basically creating aggro for a game. if(CGRectIntersectsRect(mainSprite.frame, enemy1AggroBox.frame)){ //Code here// } My plan would be to call this method in viewDidLoad. I'm not using any sort of framework like cocos2d or OpenGLES. If you need to see any more code just ask.

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TileMapRenderer in libGDX not drawing anything

- by Benjamin Dengler

So I followed the tutorial on the libGDX wiki to draw Tiled maps but it doesn't seem to render anything. Here's how I setup my OrthographicCamera and load the map: camera = new OrthographicCamera(Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); map = TiledLoader.createMap(Gdx.files.internal("maps/test.tmx")); atlas = new TileAtlas(map, Gdx.files.internal("maps")); tileMapRenderer = new TileMapRenderer(map, atlas, 8, 8); And here is my render function: Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); camera.update(); tileMapRenderer.render(camera); Also I did pack the tile map using the TiledMapPacker. I'm completely stumped... am I missing anything obvious here? EDIT: While debugging I noticed that the TileAtlas seems to be empty, which I guess shouldn't be the case, but I have no idea why it's empty.

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Bitmap font rendering, UV generation and vertex placement

- by jack

I am generating a bitmap, however, I am not sure on how to render the UV's and placement. I had a thread like this once before, but it was too loosely worded as to what I was looking to do. What I am doing right now is creating a large 1024x1024 image with characters evenly placed every 64 pixels. Here is an example of what I mean. I then save the bitmap X/Y information to a file (which is all multiples of 64). However, I am not sure how to properly use this information and bitmap to render. This falls into two different categories, UV generation and kerning. Now I believe I know how to do both of these, however, when I attempt to couple them together I will get horrendous results. For example, I am trying to render two different text arrays, "123" and "njfb". While ignoring the texture quality (I will be increasing the texture to provide more detail once I fix this issue), here is what it looks like when I try to render them. http://img64.imageshack.us/img64/599/badfontrendering.png Now for the algorithm. I am doing my letter placement with both GetABCWidth and GetKerningPairs. I am using GetABCWidth for the width of the characters, then I am getting the kerning information for adjust the characters. Does anyone have any suggestions on how I can implement my own bitmap font renderer? I am trying to do this without using external libraries such as angel bitmap tool or freetype. I also want to stick to the way the bitmap font sheet is generated so I can do extra effects in the future. Rendering Algorithm for(U32 c = 0, vertexID = 0, i = 0; c < numberOfCharacters; ++c, vertexID += 4, i += 6) { ObtainCharInformation(fontName, m_Text[c]); letterWidth = (charInfo.A + charInfo.B + charInfo.C) * scale; if(c != 0) { DWORD BytesReq = GetGlyphOutlineW(dc, m_Text[c], GGO_GRAY8_BITMAP, &gm, 0, 0, &mat); U8 * glyphImg= new U8[BytesReq]; DWORD r = GetGlyphOutlineW(dc, m_Text[c], GGO_GRAY8_BITMAP, &gm, BytesReq, glyphImg, &mat); for (int k=0; k<nKerningPairs; k++) { if ((kerningpairs[k].wFirst == previousCharIndex) && (kerningpairs[k].wSecond == m_Text[c])) { letterBottomLeftX += (kerningpairs[k].iKernAmount * scale); break; } } letterBottomLeftX -= (gm.gmCellIncX * scale); } SetVertex(letterBottomLeftX, 0.0f, zFight, vertexID); SetVertex(letterBottomLeftX, letterHeight, zFight, vertexID + 1); SetVertex(letterBottomLeftX + letterWidth, letterHeight, zFight, vertexID + 2); SetVertex(letterBottomLeftX + letterWidth, 0.0f, zFight, vertexID + 3); zFight -= 0.001f; float BottomLeftX = (F32)(charInfo.bitmapXOrigin) / (float)m_BitmapWidth; float BottomLeftY = (F32)(charInfo.bitmapYOrigin + charInfo.charBitmapHeight) / (float)m_BitmapWidth; float TopLeftX = BottomLeftX; float TopLeftY = (F32)(charInfo.bitmapYOrigin) / (float)m_BitmapWidth; float TopRightX = (F32)(charInfo.bitmapXOrigin + charInfo.B - charInfo.C) / (float)m_BitmapWidth; float TopRightY = TopLeftY; float BottomRightX = TopRightX; float BottomRightY = BottomLeftY; SetTextureCoordinate(TopLeftX, TopLeftY, vertexID + 1); SetTextureCoordinate(BottomLeftX, BottomLeftY, vertexID + 0); SetTextureCoordinate(BottomRightX, BottomRightY, vertexID + 3); SetTextureCoordinate(TopRightX, TopRightY, vertexID + 2); /// index setting letterBottomLeftX += letterWidth; previousCharIndex = m_Text[c]; }

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SpriteFont Exception, no such character?

- by Michal Bozydar Pawlowski

I have such spriteFont: <?xml version="1.0" encoding="utf-8"?>  <XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics"> <Asset Type="Graphics:FontDescription">  <FontName>Segoe UI</FontName>  <Size>20</Size>  <Spacing>0</Spacing>  <UseKerning>true</UseKerning>  <Style>Regular</Style>    <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>Ұ</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> It has the character regions (32-1200) And I get this exception: A first chance exception of type 'System.ArgumentException' occurred in Microsoft.Xna.Framework.Graphics.ni.dll The character '?' (0x0441) is not available in this SpriteFont. If applicable, adjust the font's start and end CharacterRegions to include this character. Parameter name: character Why? I'm drawing the string like this: spriteBatch.DrawString(font24, zasadyText, zasadyTextPos, kolorCzcionki1, -0.05f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.5f) I even changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception -- EDIT -- Ok, I got the solution. It was a letter mistake in language. I had this: if (jezyk == "ru_RU") { font14 = Content.Load<SpriteFont>("ru_font14"); font24 = Content.Load<SpriteFont>("ru_font24"); font12 = Content.Load<SpriteFont>("ru_czcionkaFloty"); font10 = Content.Load<SpriteFont>("ru_font10"); font28 = Content.Load<SpriteFont>("ru_font28"); font20 = Content.Load<SpriteFont>("ru_font20"); } else { font14 = Content.Load<SpriteFont>("font14"); font24 = Content.Load<SpriteFont>("font24"); font12 = Content.Load<SpriteFont>("czcionkaFloty"); font10 = Content.Load<SpriteFont>("font10"); font28 = Content.Load<SpriteFont>("font28"); font20 = Content.Load<SpriteFont>("font20"); } and there should be not "ru_RU" but "ru-RU" I have no idea. I changed the spriteFont to cyrillic: <CharacterRegions> <CharacterRegion> <Start>	</Start> <End>	</End> </CharacterRegion> <CharacterRegion> <Start> </Start> <End>ſ</End> </CharacterRegion> <CharacterRegion> <Start>А</Start> <End>ї</End> </CharacterRegion> </CharacterRegions> </Asset> </XnaContent> and it still doesn't work. I got the (0x441 = char) exception

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Need help about Drag a sprite with Animation (Cocos2d)

- by Zishan

I want to play an animation when someone drag a sprite from it's default position to another selected position. If he drag half of the selected position then animation will be play half. Example, I have 15 Frames of a animation and have a projectile arm. The projectile arm can be rotate maximum 30°, if someone rotate the arm 2° then animation sprite will be show 2nd frame, if rotate 12° then animation sprite will be show 6th frame.... and so on. Also when he release the arm, then the arm will be reverse back to it's default position and animation frames also will be reverse back to it's default first frame. I am new on cocos2d.I know how to make an animation and how to drag a sprite but I have no idea how to do this. Can anyone Please give me any idea or any tutorial how to do this, it will be very helpful for me. Thank you in advance.

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How can I do Mouse Selection In OpenGL 3.0?

- by NoobScratcher

Hello I'm pretty good programmer I've made my own 2D games in SDL and made a gui in 3D using Old OpenGL and Modern OpenGL but.. I'm having problems with trying to click 3D models with opengl I have no idea what to do too be honest. Do I read the area that I've clicked? or what do I do? 100% shore this has been asked before but I just don't know what to do...?? using : OpenGL 3.0 WIN32 API C++

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Grid pathfinding with a lot of entities

- by Vee

I'd like to explain this problem with a screenshot from a released game, DROD: Gunthro's Epic Blunder, by Caravel Games. The game is turn-based and tile-based. I'm trying to create something very similar (a clone of the game), and I've got most of the fundamentals done, but I'm having trouble implementing pathfinding. Look at the screenshot. The guys in yellow are friendly, and want to kill the roaches. Every turn, every guy in yellow pathfinds to the closest roach, and every roach pathfinds to the closest guy in yellow. By closest I mean the target with the shortest path, not a simple distance calculation. All of this without any kind of slowdown when loading the level or when passing turns. And all of the entities change position every turn. Also (not shown in screenshot), there can be doors that open and close and change the level's layout. Impressive. I've tried implementing pathfinding in my clone. First attempt was making every roach find a path to a yellow guy every turn, using a breadth-first search algorithm. Obviously incredibly slow with more than a single roach, and would get exponentially slower with more than a single yellow guy. Second attempt was mas making every yellow guy generate a pathmap (still breadth-first search) every time he moved. Worked perfectly with multiple roaches and a single yellow guy, but adding more yellow guys made the game slow and unplayable. Last attempt was implementing JPS (jump point search). Every entity would individually calculate a path to its target. Fast, but with a limited number of entities. Having less than half the entities in the screenshot would make the game slow. And also, I had to get the "closest" enemy by calculating distance, not shortest path. I've asked on the DROD forums how they did it, and a user replied that it was breadth-first search. The game is open source, and I took a look at the source code, but it's C++ (I'm using C#) and I found it confusing. I don't know how to do it. Every approach I tried isn't good enough. And I believe that DROD generates global pathmaps, somehow, but I can't understand how every entity find the best individual path to other entities that move every turn. What's the trick? This is a reply I just got on the DROD forums: Without having looked at the code I'd wager it's two (or so) pathmaps for the whole room: One to the nearest enemy, and one to the nearest friendly for every tile. There's no need to make a separate pathmap for every entity when the overall goal is "move towards nearest enemy/friendly"... just mark every tile with the number of moves it takes to the nearest target and have the entity chose the move that takes it to the tile with the lowest number. To be honest, I don't understand it that well.

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Aw, Snap! in Google Chrome [on hold]

- by D. S. Schneider

Just wondering if anyone else's experiencing the "Aw, Snap!" bug in Google Chrome. I'm developing a brand new engine which occasionaly triggers this bug and as far as I know, there's nothing one can do to find out what actually triggered the issue. I've also tested my engine with Firefox, which runs just fine. Anyway, just wanted to know if someone else is facing this while developing games for Google Chrome and has a clue about what can be done to avoid it. I'm using plain JavaScript and the audio and canvas elements from HTML5. Thanks!

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Low coupling and tight cohesion

- by hidayat

Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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Acceptable GC frequency for a SlimDX/Windows/.NET game?

- by Rei Miyasaka

I understand that the Windows GC is much better than the Xbox/WP7 GC, being that it's generational and multithreaded -- so I don't need to worry quite as much about avoiding memory allocation. SlimDX even has some unavoidable functions that generate some amount of garbage (specifically, MapSubresource creates DataBoxes), yet people don't seem to be too upset about it. I'd like to use some functional paradigms to write my code too, which also means creating objects like closures and monads. I know premature optimization isn't a good thing, but are there rules of thumb or metrics that I can follow to know whether I need to cut down on allocations? Is, say, one gen 0 GC per frame too much? One thing that has me stumped is object promotions. Gen 0 GCs will supposedly finish within a millisecond or two, but if I'm understanding correctly, it's the gen 1 and 2 promotions that start to hurt. I'm not too sure how I can predict/prevent these.

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GoogleAppEngine : ClassNotFoundException : javax.jdo.metadata.ComponentMetadata

- by James.Elsey

I'm trying to deploy my application to a locally running GoogleAppEngine development server, but I'm getting the following stack trace when I start the server Apr 23, 2010 9:03:33 PM com.google.apphosting.utils.jetty.JettyLogger warn WARNING: Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'clientDao' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Cannot resolve reference to bean 'entityManagerFactory' while setting bean property 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: javax/jdo/metadata/ComponentMetadata: java.lang.ClassNotFoundException: javax.jdo.metadata.ComponentMetadata at java.net.URLClassLoader$1.run(URLClassLoader.java:217) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:319) at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:151) at java.lang.ClassLoader.loadClass(ClassLoader.java:264) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2009) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2007) at java.security.AccessController.doPrivileged(Native Method) at javax.jdo.JDOHelper.forName(JDOHelper.java:2006) at javax.jdo.JDOHelper.invokeGetPersistenceManagerFactoryOnImplementation(JDOHelper.java:1155) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:803) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:698) at org.datanucleus.jpa.EntityManagerFactoryImpl.initialisePMF(EntityManagerFactoryImpl.java:482) at org.datanucleus.jpa.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:255) at org.datanucleus.store.appengine.jpa.DatastoreEntityManagerFactory.<init>(DatastoreEntityManagerFactory.java:68) at org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider.createContainerEntityManagerFactory(DatastorePersistenceProvider.java:45) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:224) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:291) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1245) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:530) at org.mortbay.jetty.servlet.Context.startContext(Context.java:135) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1218) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:500) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.jetty.Server.doStart(Server.java:217) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:181) at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:116) at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:217) at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:162) at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48) at com.google.appengine.tools.development.DevAppServerMain.<init>(DevAppServerMain.java:113) at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:89) The server is running at http://localhost:1234/ I'm a little confused over this, since I have the same application running locally on GlassFish/MySQL. All I have done is to swap in the relevant jar files, and change the persistence.xml. My applicationContext.xml looks as follows : <context:annotation-config/> <bean id="clientDao" class="com.jameselsey.salestracker.dao.jpa.JpaDaoClient"> <property name="entityManagerFactory" ref="entityManagerFactory"/> </bean> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"/> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> <bean id="org.springframework.context.annotation.internalPersistenceAnnotationProcessor" class="com.jameselsey.salestracker.util.GaeFixInternalPersistenceAnnotationProcessor" /> <bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"/> <tx:annotation-driven/> <bean id="clientService" class="com.jameselsey.salestracker.service.ClientService"/> </beans> My JPA DAO looks like this public class JpaDao extends JpaDaoSupport { protected <T> List<T> findAll(Class<T> clazz) { return getJpaTemplate().find("select c from " + clazz.getName() + " c"); } protected <T> T findOne(String jpql, Map params) { List<T> results = getJpaTemplate().findByNamedParams(jpql, params); if(results.isEmpty()) { return null; } if(results.size() > 1) { throw new IncorrectResultSizeDataAccessException(1, results.size()); } return results.get(0); } } And an example implemented method looks like this : @Override public Client getClientById(Integer clientId) { String jpql = "SELECT c " + "FROM com.jameselsey.salestracker.domain.Client c " + "WHERE c.id = " + clientId; return (Client) getJpaTemplate().find(jpql).get(0); } Like I say, this works ok on Glassfish/MySQL, is it possible this error could be a red herring to something else?

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Narrow-phase collision detection algorithms

- by Marian Ivanov

There are three phases of collision detection. Broadphase: It loops between all objecs that can interact, false positives are allowed, if it would speed up the loop. Narrowphase: Determines whether they collide, and sometimes, how, no false positives Resolution: Resolves the collision. The question I'm asking is about the narrowphase. There are multiple algorithms, differing in complexity and accuracy. Hitbox intersection: This is an a-posteriori algorithm, that has the lowest complexity, but also isn't too accurate, Color intersection: Hitbox intersection for each pixel, a-posteriori, pixel-perfect, not accuratee in regards to time, higher complexity Separating axis theorem: This is used more often, accurate for triangles, however, a-posteriori, as it can't find the edge, when taking last frame in account, it's more stable Linear raycasting: A-priori algorithm, useful for semi-realistic-looking physics, finds the intersection point, even more accurate than SAT, but with more complexity Spline interpolation: A-priori, even more accurate than linear rays, even more coplexity. There are probably many more that I've forgot about. The question is, in when is it better to use SAT, when rays, when splines, and whether there is anything better.

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OpenGL Shading Program Object Memory Requirement

- by Hans Wurst

gDEbugger states that OpenGL's program objects only occupy an insignificant amount of memory. How much is this actually? I don't know if the stuff I looked up in mesa is actually that I was looking for but it requires 16KB [Edit: false, confusing struct names, less than 1KB immediate, some further behind pointers] per program object. Not quite insignificant. So is it recommended to create a unique program object for each object of the scene? Or to share a single program object and set the scene's object's custom variables just before its draw call?

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Is there a global "low resolution" filter for OpenGL?

- by Ian Henry

I'm trying to learn a little about OpenGL, so I'm making a simple 2D game (with OpenTK), and so far it's coming along well. I thought it would be fun to give it that, for lack of a better word, retropixelated look of games from the early nineties. I figured it would be an easy thing to do -- simply draw everything at half its normal size and scale up with no anti-aliasing. But I can't find any resources on how to do this. I can set the min/mag filters of my textures to nearest and that works fine for my sprites, but I'm using lots of primitives and I'd like the effect to apply to them as well. The one idea I had was to draw everything at half size, then somehow copy the render buffer to a texture, then render that texture full-size, but I don't know how to do that, and it seems like there must be a better way. Can anyone help me out?

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Better way to do AI Behavior in AS3/Flixel

- by joon

I'm making a game in Flixel and I need to program an NPC. It's rapidly turning more complex than I expected. I was wondering if there are any best practices, tutorials or examples that you can refer me to, to see how this is done. I can probably hack it together, which is what I always do, but it would be nice if I can make it maintanable and can add stuff later on. Here's screenshot to give you an idea: The butler will be an NPC that will follow you, or guide you, and talk to you the whole time. EDIT: More specifically: What I have now is a long list of IF statements in the update loop of the butler (about 8 different cases), and all I have covered is his walking behavior. I want him to comment on things and sometimes switch his main behavior to be more aggresive or distant,... Is there any way to keep track of this, or is complex code with many many nested if statements the way to go?

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Bullet Physic: Transform body after adding

- by Mathias Hölzl

I would like to transform a rigidbody after adding it to the btDiscreteDynamicsWorld. When I use the CF_KINEMATIC_OBJECT flag I am able to transform it but it's static (no collision response/gravity). When I don't use the CF_KINEMATIC_OBJECT flag the transform doesn't gets applied. So how to I transform non-static objects in bullet? DemoCode: btBoxShape* colShape = new btBoxShape(btVector3(SCALING*1,SCALING*1,SCALING*1)); /// Create Dynamic Objects btTransform startTransform; startTransform.setIdentity(); btScalar mass(1.f); //rigidbody is dynamic if and only if mass is non zero, otherwise static bool isDynamic = (mass != 0.f); btVector3 localInertia(0,0,0); if (isDynamic) colShape->calculateLocalInertia(mass,localInertia); btDefaultMotionState* myMotionState = new btDefaultMotionState(); btRigidBody::btRigidBodyConstructionInfo rbInfo(mass,myMotionState,colShape,localInertia); btRigidBody* body = new btRigidBody(rbInfo); body->setCollisionFlags(body->getCollisionFlags()|btCollisionObject::CF_KINEMATIC_OBJECT); body->setActivationState(DISABLE_DEACTIVATION); m_dynamicsWorld->addRigidBody(body); startTransform.setOrigin(SCALING*btVector3( btScalar(0), btScalar(20), btScalar(0) )); body->getMotionState()->setWorldTransform(startTransform);

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