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• Problem when scaling game screen in Libgdx

  - by Nicolas Martel

  Currently, I'm able to scale the screen by applying this bit of code onto an OrthographicCamera Camera.setToOrtho(true, Gdx.graphics.getWidth() / 2, Gdx.graphics.getHeight() / 2); But something quite strange is happening with this solution, take a look at this picture of my game below Seems fine right? But upon further investigation, many components are rendered off by one pixels, and the tiles all are. Take a closer look I circled a couple of the errors. Note that the shadow of the warrior I circled appears fine for the other warriors. Also keep in mind that everything is rendered at pixel-perfect precision when I disable the scaling. I actually thought of a possible source for the problem as I'm writing this but I decided to still post this because I would assume somebody else might run into the same issue.

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• Quaternion based rotation and pivot position

  - by Michael IV

  I can't figure out how to perform matrix rotation using Quaternion while taking into account pivot position in OpenGL.What I am currently getting is rotation of the object around some point in the space and not a local pivot which is what I want. Here is the code [Using Java] Quaternion rotation method: public void rotateTo3(float xr, float yr, float zr) { _rotation.x = xr; _rotation.y = yr; _rotation.z = zr; Quaternion xrotQ = Glm.angleAxis((xr), Vec3.X_AXIS); Quaternion yrotQ = Glm.angleAxis((yr), Vec3.Y_AXIS); Quaternion zrotQ = Glm.angleAxis((zr), Vec3.Z_AXIS); xrotQ = Glm.normalize(xrotQ); yrotQ = Glm.normalize(yrotQ); zrotQ = Glm.normalize(zrotQ); Quaternion acumQuat; acumQuat = Quaternion.mul(xrotQ, yrotQ); acumQuat = Quaternion.mul(acumQuat, zrotQ); Mat4 rotMat = Glm.matCast(acumQuat); _model = new Mat4(1); scaleTo(_scaleX, _scaleY, _scaleZ); _model = Glm.translate(_model, new Vec3(_pivot.x, _pivot.y, 0)); _model =rotMat.mul(_model);//_model.mul(rotMat); //rotMat.mul(_model); _model = Glm.translate(_model, new Vec3(-_pivot.x, -_pivot.y, 0)); translateTo(_x, _y, _z); notifyTranformChange(); } Model matrix scale method: public void scaleTo(float x, float y, float z) { _model.set(0, x); _model.set(5, y); _model.set(10, z); _scaleX = x; _scaleY = y; _scaleZ = z; notifyTranformChange(); } Translate method: public void translateTo(float x, float y, float z) { _x = x - _pivot.x; _y = y - _pivot.y; _z = z; _position.x = _x; _position.y = _y; _position.z = _z; _model.set(12, _x); _model.set(13, _y); _model.set(14, _z); notifyTranformChange(); } But this method in which I don't use Quaternion works fine: public void rotate(Vec3 axis, float angleDegr) { _rotation.add(axis.scale(angleDegr)); // change to GLM: Mat4 backTr = new Mat4(1.0f); backTr = Glm.translate(backTr, new Vec3(_pivot.x, _pivot.y, 0)); backTr = Glm.rotate(backTr, angleDegr, axis); backTr = Glm.translate(backTr, new Vec3(-_pivot.x, -_pivot.y, 0)); _model =_model.mul(backTr);///backTr.mul(_model); notifyTranformChange(); }

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• Confusion about Rotation matrices from Euler Angles

  - by xEnOn

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

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• Image 1 becomes image 2 with sliding effect from left to right?

  - by Paul

  I would like to show a second image appearing while a "door" is closing on my character. I've got my character in the middle of the screen and a door coming from the left. When the door passes my character, I would like to have this second image appearing little by little. So far, I've gotten by with fadingOut the character and then fadingIn my second image of the character at the same position when the door is completely closed, but I would like to have both of them at the same time. (the effect that image 1 becomes image 2 when the door is sliding from left to right). Would you know how to do this with Cocos2d? Here are the images : at first, the character is blue, and the door is coming from the left : Then, behind the black door, the character becomes red, but only behind this door, so it stays blue when the door is not on him, and will become completely red when the door passes the character : EDIT : with this code, the black door hides the red and blue rectangles : (And if i add each of my layers at a different depth, and only use GL_LESS, same thing) blue.position = ccp( size.width*0.5 , size.height/2 ); red.position = ccp( size.width*0.46 , size.height/2 ); black.position = ccp( size.width*0.1 , size.height/2 ); glEnable(GL_DEPTH_TEST); [batch addChild:red z:0]; [batch addChild:black z:2]; glDepthFunc(GL_GREATER); [batch addChild:blue z:1]; glDepthFunc(GL_LESS); id action1 = [CCMoveTo actionWithDuration:3 position:ccp(size.width,size.height/2)]; [black runAction: [CCSequence actions:action1, nil]];

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• Collision planes confusion

  - by Jeffrey

  I'm following this tutorial by thecplusplusguy and in the linked video he explain that for example for the world basement and walls we need to create the actual rendered (shown to the player) walls and then duplicate them, place them in the same coordinates as the rendered walls and call them collision (by defining their material to collision). Then it defines in the Object loader function that those objects with material == collision are collision planes and should not be rendered but just used to check collision. Now I'm pretty confused. Why would we add this kind of complexity to a problem that can easily be solved by a simple loadObject(string plane_object, bool check_collision);: Creating only the walls object (by loading .obj file in plane_object) Define them also as collision planes whenever the check_collision is set to true In this case we have lowered the complexity of his method and make it more flexible and faster to develop (faster because we don't always have to make a copy for each plane and flexible because we don't hardcode the Object loader). The only case in which this method could not work is when we need hidden collision planes, and for that we could modify the loadObject() function like this: loadObject(string plane_object, bool check_collision = true, bool hide_object = false); Creating only the walls object (by loading .obj file in plane_object) Define them also as collision planes whenever the check_collision is set to true And add the ability to actually show the object or hide it based on hide_object. The final question is: am I right? What would the possible problem encountered with my solution versus his?

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• how to properly implement alpha blending in a complex 3d scene

  - by Gajet

  I know this question might sound a bit easy to answer but It's driving me crazy. There are too many possible situations that a good alpha blending mechanism should handle, and for each Algorithm I can think of there is something missing. these are the methods I've though about so far: first of I though about object sorting by depth, this one simply fails because Objects are not simple shapes, they might have curves and might loop inside each other. so I can't always tell which one is closer to camera. then I thought about sorting triangles but this one also might fail, thought I'm not sure how to implement it there is a rare case that might again cause problem, in which two triangle pass through each other. again no one can tell which one is nearer. the next thing was using depth buffer, at least the main reason we have depth buffer is because of the problems with sorting that I mentioned but now we get another problem. Since objects might be transparent, in a single pixel there might be more than one object visible. So for which Object should I store pixel depth? I then thought maybe I can only store the most front Object depth, and using that determine how should I blend next draw calls at that pixel. But again there was a problem, think about 2 semi transparent planes with a solid plane in middle of them. I was going to render the solid plane at the end, one can see the most distant plane. note that I was going to merge every two planes until there is only one color left for that pixel. Obviously I can use sorting methods too because of the same reasons I've explained above. Finally the only thing I imagine being able to work is to render all objects into different render targets and then sort those layers and display the final output. But this time I don't know how can I implement this algorithm.

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• Lightning whip particle effects

  - by Fibericon

  I'm currently using Mercury Particle Engine for the particle effects in my game, and I'm trying to create a sort of lightning whip - basically a lightning effect bound to a line that curves when the player moves. I know how to use the editor, and I have particle effects working in game. However, I'm completely lost as to where I should start for this specific particle effect. Perhaps if I could find the code for it in a different particle engine, I could convert it, but I can't seem to find that either. What I did find was a lot of tutorials for creating the lines associated with lightning programmatically, which doesn't help in this case because I don't want it to be rigid. Perhaps it would be more like some sort of laser beam with crackling effects around it? I'm running into a wall as far as even beginning to implement this goes.

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• I am looking to create realistic car movement using vectors

  - by bobthemac

  I have goggled how to do this and found this http://www.helixsoft.nl/articles/circle/sincos.htm I have had a go at it but most of the functions that were showed didn't work I just got errors because they didn't exist. I have looked at the cos and sin functions but don't understand how to use them or how to get the car movement working correctly using vectors. I have no code because I am not sure what to do sorry. Any help is appreciated. EDIT: I have restrictions that I must use the TL engine for my game, I am not allowed to add any sort of physics engine. It must be programmed in c++. Here is a sample of what i got from trying to follow what was done in the link I provided. if(myEngine->KeyHeld(Key_W)) { length += carSpeedIncrement; } if(myEngine->KeyHeld(Key_S)) { length -= carSpeedIncrement; } if(myEngine->KeyHeld(Key_A)) { angle -= carSpeedIncrement; } if(myEngine->KeyHeld(Key_D)) { angle += carSpeedIncrement; } carVolocityX = cos(angle); carVolocityZ = cos(angle); car->MoveX(carVolocityX * frameTime); car->MoveZ(carVolocityZ * frameTime);

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• Physic engine for snooker/billard game

  - by Marc Gillé

  I think most billard/snooker games have a lot of problems with their physic engines. They are far away from realistic and you can't really enjoy the game (especially when snooker is your hobby :) ) So I want to try to make an own physic engine (and own snooker game). I think the physic engine is the most important part of such a game. So my question is: Do anybody know an open physic enginge I can start with? Is there any literature about such physic problems?

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• How should I account for the GC when building games with Unity?

  - by Eonil

  *As far as I know, Unity3D for iOS is based on the Mono runtime and Mono has only generational mark & sweep GC. This GC system can't avoid GC time which stops game system. Instance pooling can reduce this but not completely, because we can't control instantiation happens in the CLR's base class library. Those hidden small and frequent instances will raise un-deterministic GC time eventually. Forcing complete GC periodically will degrade performance greatly (can Mono force complete GC, actually?) So, how can I avoid this GC time when using Unity3D without huge performance degrade?

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• Switching songs - MediaPlayer lags the game

  - by Fibericon

  When the player encounters a boss in the game I'm working on, I want to have the music change. It seems simple enough with the MediaPlayer class to fade out the current song, switch to another, and then fade the new song in. However, at the point where the second song starts, the game freezes for a split second. The songs in question aren't particularly large either - the first song is 1.7mb and the second song is 3.1mb, both mp3 format. This is the code I'm using to do it: protected void switchSong(GameTime gameTime) { if (!bossSongPlaying) { MediaPlayer.Volume -= ((float)gameTime.ElapsedGameTime.TotalSeconds/10); if (MediaPlayer.Volume < 0.05f) { MediaPlayer.Play(bossSong); MediaPlayer.Volume = 1.0f; bossSongPlaying = true; } } } What can I do to eliminate that momentary hang?

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• How should bots be recognised in a game?

  - by Bane

  I'm interested in how bots are usually written. Here's my situation: I plan to make an online 2D mecha game in HTML5, and the server-side will be done with node. It is intended to be multiplayer, but I also want to make bots in case there aren't enough players. How does my game logic see them, as players or as bots? Is there a standard by which I should make them? Also, any general tips and hints will be OK.

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• Where to implement storable items

  - by James Hay

  I'm creating a multiplayer online trading game. The things that are traded range from raw items to complex products. For example Steel is a raw item. Mechanical Assembly is a more complex item that requires 2x Steel and maybe 1x Rubber. Then Hydraulics is an item that contains 2x Mechanical Assemblies and 1x Electronics (which is another complex item). So and so forth. These items will be created by me, players can't create their own items, so it doesn't need to be able to handle arbitrary layers of complexity for items. If my example isn't clear, think Minecraft. You have wooden planks, which can be made into sticks. From there the sticks - combined with metals - can be made into tools. My game is nothing to do with minecraft or any sandbox building game, but it uses a similar progressive complexity to creating items that I want to have in my game. My question is basically, how do you store something like this assuming that I will want to add more items in the future? Do you store it in a database or in a seperate library that the game uses? EDIT None of the items actually "do" anything, they are simply there to either sell, purchase, or combine with other items to make a more complex item, which can then be sold, purchased or combined... you get the idea. The items themselves would not have any properties, but the instances of the items would. For example an item that one player has would have a certain "quality" and if they were selling it a certain "price". An instance of that same item that a different player had would need to have a different "quality" and "price" if they were selling it. I think the price part will not be required on an individual item because instead I would have a "sale" object which was for a price and contained certain items.

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• Geometry Shader : points + Triangles

  - by CmasterG

  I have different Shaders and for each Shader a instance of the ShaderClass class, which initializes the Shaders, Renders the Shaders, etc. I use most of the Shaderclasses without Geometry Shader, but in one Shader Class i also use a Geometry Shader. The problem is, that when I render one object with the Shaderclass that uses the Geometry shader, all other object are rendered with the same geometry that I create in the Geometry Shader. Can you help me? Is it possible that I have to use a Geometry Shader for each object, when I use one for one object? I use DirectX 11 with C++.

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• Adaptive Characters: AI Solution Needs a Problem

  - by Roger F. Gay

  Have sophisticated adaptive programming, will travel - so to speak. I'm part of a group that developed sophisticated learning / adaptive software for robotics. The system "thinks" via its simulator, building and adapting code on its own; and then carries out the best solution. The software can also adapt to new situations, etc. http://mensnewsdaily.com/2007/05/16/robobusiness-robots-with-imagination/ It's easy to imagine using it with automated game characters that will adapt to the players moves and style - the easiest example would be fighting. The more the simulated fighter fights with the human player, the more it learns to counter that players fighting skills. But there should be more. Anyone have any ideas as to how adaptive characters might be interesting in games?

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• 2D scene graph not transforming relative to parent

  - by Dr.Denis McCracleJizz

  I am currently in the process of coding my own 2D Scene graph, which is basically a port of flash's render engine. The problem I have right now is my rendering doesn't seem to be working properly. This code creates the localTransform property for each DisplayObject. Matrix m_transform = Matrix.CreateRotationZ(rotation) * Matrix.CreateScale(scaleX, scaleY, 1) * Matrix.CreateTranslation(new Vector3(x, y, z)); This is my render code. float dRotation; Vector2 dPosition, dScale; Matrix transform; transform = this.localTransform; if (parent != null) transform = localTransform * parent.localTransform; DecomposeMatrix(ref transform, out dPosition, out dRotation, out dScale); spriteBatch.Draw(this.texture, dPosition, null, Color.White, dRotation, new Vector2(originX, originY), dScale, SpriteEffects.None, 0.0f); Here is the result when I try to add the Stage then to the stage a First DisplayObjectContainer and then a second one. It may look fine but the problem lies in the fact that I add a first DisplayObjectContainer at (400,400) and the second one within it (that's the smallest one) at position (0,0). So he should be right over its parent but he gets render within the parent at the same position the parent has (400, 400) for some reason. It's just as if I double the parent's localMatrix and then render the second cat there. This is the code i use to loop through every childs. base.Draw(spriteBatch); foreach (DisplayObject childs in _childs) { childs.Draw(spriteBatch); }

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• How to capture the screen in DirectX 9 to a raw bitmap in memory without using D3DXSaveSurfaceToFile

  - by cloudraven

  I know that in OpenGL I can do something like this glReadBuffer( GL_FRONT ); glReadPixels( 0, 0, _width, _height, GL_RGB, GL_UNSIGNED_BYTE, _buffer ); And its pretty fast, I get the raw bitmap in _buffer. When I try to do this in DirectX. Assuming that I have a D3DDevice object I can do something like this if (SUCCEEDED(D3DDevice->GetBackBuffer(0, 0, D3DBACKBUFFER_TYPE_MONO, &pBackbuffer))) { HResult hr = D3DXSaveSurfaceToFileA(filename, D3DXIFF_BMP, pBackbuffer, NULL, NULL); But D3DXSaveSurfaceToFile is pretty slow, and I don't need to write the capture to disk anyway, so I was wondering if there was a faster way to do this

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• XNA Drag Gestures - fractional delta values

  - by Den

  I have an issue with objects moving roughly twice as far as expected when dragging them. I am comparing my application to the standard TouchGestureSample sample from MSDN. For some reason in my application gesture samples have fractional positions and deltas. Both are using same Microsoft.Xna.Framework.Input.Touch.dll, v4.0.30319. I am running both apps using standard Windows Phone Emulator. I am setting my break point immediately after this line of code in a simple Update method: GestureSample gesture = TouchPanel.ReadGesture(); Typical values in my app: Delta = {X:-13.56522 Y:4.166667} Position = {X:184.6956 Y:417.7083} Typical values in sample app: Delta = {X:7 Y:16} Position = {X:497 Y:244} Have anyone seen this issue? Does anyone have any suggestions? Thank you.

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• My frustum culling is culling from the wrong point [SOLVED]

  - by Xbetas

  I'm having problems with my frustum being in the wrong origin. It follows the rotation of my camera but not the position. In my camera class I'm generating a view-matrix: void Camera::Update() { UpdateViewMatrix(); glMatrixMode(GL_MODELVIEW); //glLoadIdentity(); glLoadMatrixf(GetViewMatrix().m); } Then extracting the planes using the projection matrix and modelview matrix: void UpdateFrustum() { Matrix4x4 projection, model, clip; glGetFloatv(GL_PROJECTION_MATRIX, projection.m); glGetFloatv(GL_MODELVIEW_MATRIX, model.m); clip = model * projection; m_Planes[RIGHT][0] = clip.m[ 3] - clip.m[ 0]; m_Planes[RIGHT][1] = clip.m[ 7] - clip.m[ 4]; m_Planes[RIGHT][2] = clip.m[11] - clip.m[ 8]; m_Planes[RIGHT][3] = clip.m[15] - clip.m[12]; NormalizePlane(RIGHT); m_Planes[LEFT][0] = clip.m[ 3] + clip.m[ 0]; m_Planes[LEFT][1] = clip.m[ 7] + clip.m[ 4]; m_Planes[LEFT][2] = clip.m[11] + clip.m[ 8]; m_Planes[LEFT][3] = clip.m[15] + clip.m[12]; NormalizePlane(LEFT); m_Planes[BOTTOM][0] = clip.m[ 3] + clip.m[ 1]; m_Planes[BOTTOM][1] = clip.m[ 7] + clip.m[ 5]; m_Planes[BOTTOM][2] = clip.m[11] + clip.m[ 9]; m_Planes[BOTTOM][3] = clip.m[15] + clip.m[13]; NormalizePlane(BOTTOM); m_Planes[TOP][0] = clip.m[ 3] - clip.m[ 1]; m_Planes[TOP][1] = clip.m[ 7] - clip.m[ 5]; m_Planes[TOP][2] = clip.m[11] - clip.m[ 9]; m_Planes[TOP][3] = clip.m[15] - clip.m[13]; NormalizePlane(TOP); m_Planes[NEAR][0] = clip.m[ 3] + clip.m[ 2]; m_Planes[NEAR][1] = clip.m[ 7] + clip.m[ 6]; m_Planes[NEAR][2] = clip.m[11] + clip.m[10]; m_Planes[NEAR][3] = clip.m[15] + clip.m[14]; NormalizePlane(NEAR); m_Planes[FAR][0] = clip.m[ 3] - clip.m[ 2]; m_Planes[FAR][1] = clip.m[ 7] - clip.m[ 6]; m_Planes[FAR][2] = clip.m[11] - clip.m[10]; m_Planes[FAR][3] = clip.m[15] - clip.m[14]; NormalizePlane(FAR); } void NormalizePlane(int side) { float length = 1.0/(float)sqrt(m_Planes[side][0] * m_Planes[side][0] + m_Planes[side][1] * m_Planes[side][1] + m_Planes[side][2] * m_Planes[side][2]); m_Planes[side][0] *= length; m_Planes[side][1] *= length; m_Planes[side][2] *= length; m_Planes[side][3] *= length; } And check against it with: bool PointInFrustum(float x, float y, float z) { for(int i = 0; i < 6; i++) { if( m_Planes[i][0] * x + m_Planes[i][1] * y + m_Planes[i][2] * z + m_Planes[i][3] <= 0 ) return false; } return true; } Then i render using: camera->Update(); UpdateFrustum(); int numCulled = 0; for(int i = 0; i < (int)meshes.size(); i++) { if(!PointInFrustum(meshCenter.x, meshCenter.y, meshCenter.z)) { meshes[i]->SetDraw(false); numCulled++; } else meshes[i]->SetDraw(true); } Matrices look like (Camera is at (5, 0, 0)): ModelView [0,0,0.99,0] [0,1,0,0] [-0.99,0,0,0] [0,0,-5,1] Projection [0.814,0,0,0] [0,1.303,0,0] [0,0,-1,0] [0,0,-0.02,0] Clip [0,0,-1,-0.999] [0,1.30,0,0] [-0.814,0,0,0] [0,0,4.98,4.99] What am i doing wrong?

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• What are the different ways to texture a terrain?

  - by ApocKalipsS

  I'm working with XNA on a 3D Game, and I'm trying to have a proper and nice environnement. I actually followed a tutorial to create a terrain from a Heightmap, and to texture it, I just apply a grass texture on it and tile it a number of times. But what I want to do is to have a really realistic texturing, but also generate it automatically (for example if I want to use a perlin noise to generate a terrain and then texture it). I already learnt about multi-texturing, loading a map file with different colors for different textures, but I don't think this is really efficient, for instance for cliffs or very steep areas it will tile a texture badly as it's a view from the top. Also I don't know how i'll draw roads or dirt paths with that. I hope you understood me despite my english! If you don't, basically, here what I want to do: How do I texture a randomly generated terrain? :) Thank you for your answers!

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• Manually updating HTML5 local storage?

  - by hustlerinc

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

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• Is it possible to construct a cube with less than 24 vertices

  - by Telanor

  I have a cube-based world like minecraft and I'm wondering if there's a way to construct a cube with less than 24 vertices so I can reduce memory usage. It doesn't seem possible to me for 2 reasons: the normals wouldn't come out right and per-face textures wouldn't work. Is this the case or am I wrong? Maybe there's some fancy new dx11 tech that can help? Edit: Just to clarify, I have 2 requirements: I need surface normals for each cube face in order to do proper lighting and I need a way to address a different indexes in a texture array for each cube face

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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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• OpenGL 3 and the Radeon HD 4850x2

  - by rotard

  A while ago, I picked up a copy of the OpenGL SuperBible fifth edition and slowly and painfully started teaching myself OpenGL the 3.3 way, after having been used to the 1.0 way from school way back when. Making things more challenging, I am primarily a .NET developer, so I was working in Mono with the OpenTK OpenGL wrapper. On my laptop, I put together a program that let the user walk around a simple landscape using a couple shaders that implemented per-vertex coloring and lighting and texture mapping. Everything was working brilliantly until I ran the same program on my desktop. Disaster! Nothing would render! I have chopped my program down to the point where the camera sits near the origin, pointing at the origin, and renders a square (technically, a triangle fan). The quad renders perfectly on my laptop, coloring, lighting, texturing and all, but the desktop renders a small distorted non-square quadrilateral that is colored incorrectly, not affected by the lights, and not textured. I suspect the graphics card is at fault, because I get the same result whether I am booted into Ubuntu 10.10 or Win XP. I did find that if I pare the vertex shader down to ONLY outputting the positional data and the fragment shader to ONLY outputting a solid color (white) the quad renders correctly. But as SOON as I start passing in color data (whether or not I use it in the fragment shader) the output from the vertex shader is distorted again. The shaders follow. I left the pre-existing code in, but commented out so you can get an idea what I was trying to do. I'm a noob at glsl so the code could probably be a lot better. My laptop is an old lenovo T61p with a Centrino (Core 2) Duo and an nVidia Quadro graphics card running Ubuntu 10.10 My desktop has an i7 with a Radeon HD 4850 x2 (single card, dual GPU) from Saphire dual booting into Ubuntu 10.10 and Windows XP. The problem occurs in both XP and Ubuntu. Can anyone see something wrong that I am missing? What is "special" about my HD 4850x2? string vertexShaderSource = @" #version 330 precision highp float; uniform mat4 projection_matrix; uniform mat4 modelview_matrix; //uniform mat4 normal_matrix; //uniform mat4 cmv_matrix; //Camera modelview. Light sources are transformed by this matrix. //uniform vec3 ambient_color; //uniform vec3 diffuse_color; //uniform vec3 diffuse_direction; in vec4 in_position; in vec4 in_color; //in vec3 in_normal; //in vec3 in_tex_coords; out vec4 varyingColor; //out vec3 varyingTexCoords; void main(void) { //Get surface normal in eye coordinates //vec4 vEyeNormal = normal_matrix * vec4(in_normal, 0); //Get vertex position in eye coordinates //vec4 vPosition4 = modelview_matrix * vec4(in_position, 0); //vec3 vPosition3 = vPosition4.xyz / vPosition4.w; //Get vector to light source in eye coordinates //vec3 lightVecNormalized = normalize(diffuse_direction); //vec3 vLightDir = normalize((cmv_matrix * vec4(lightVecNormalized, 0)).xyz); //Dot product gives us diffuse intensity //float diff = max(0.0, dot(vEyeNormal.xyz, vLightDir.xyz)); //Multiply intensity by diffuse color, force alpha to 1.0 //varyingColor.xyz = in_color * diff * diffuse_color.xyz; varyingColor = in_color; //varyingTexCoords = in_tex_coords; gl_Position = projection_matrix * modelview_matrix * in_position; }"; string fragmentShaderSource = @" #version 330 //#extension GL_EXT_gpu_shader4 : enable precision highp float; //uniform sampler2DArray colorMap; //in vec4 varyingColor; //in vec3 varyingTexCoords; out vec4 out_frag_color; void main(void) { out_frag_color = vec4(1,1,1,1); //out_frag_color = varyingColor; //out_frag_color = vec4(varyingColor, 1) * texture(colorMap, varyingTexCoords.st); //out_frag_color = vec4(varyingColor, 1) * texture(colorMap, vec3(varyingTexCoords.st, 0)); //out_frag_color = vec4(varyingColor, 1) * texture2DArray(colorMap, varyingTexCoords); }"; Note that in this code the color data is accepted but not actually used. The geometry is outputted the same (wrong) whether the fragment shader uses varyingColor or not. Only if I comment out the line varyingColor = in_color; does the geometry output correctly. Originally the shaders took in vec3 inputs, I only modified them to take vec4s while troubleshooting.

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• How can I achieve a 3D-like effect with spritebatch's rotation and scale parameters

  - by Alic44

  I'm working on a 2d game with a top-down perspective similar to Secret of Mana and the 2D Final Fantasy games, with one big difference being that it's an action rpg using a 3-dimensional physics engine. I'm trying to draw an aimer graphic (basically an arrow) at my characters' feet when they're aiming a ranged weapon. At first I just converted the character's aim vector to radians and passed that into spritebatch, but there was a problem. The position of every object in my world is scaled for perspective when it's drawn to the screen. So if the physics engine coordinates are (1, 0, 1), the screen coords are actually (1, .707) -- the Y and Z axis are scaled by a perspective factor of .707 and then added together to get the screen coordinates. This meant that the direction the aimer graphic pointed (thanks to its rotation value passed into spritebatch) didn't match up with the direction the projectile actually traveled over time. Things looked fine when the characters fired left, right, up, or down, but if you fired on a diagonal the perspective of the physics engine didn't match with the simplistic way I was converting the character's aim direction to a screen rotation. Ok, fast forward to now: I've got the aimer's rotation matched up with the path the projectile will actually take, which I'm doing by decomposing a transform matrix which I build from two rotation matrices (one to represent the aimer's rotation, and one to represent the camera's 45 degree rotation on the x axis). My question is, is there a way to get not just rotation from a series of matrix transformations, but to also get a Vector2 scale which would give the aimer the appearance of being a 3d object, being warped by perspective? Orthographic perspective is what I'm going for, I think. So, the aimer arrow would get longer when facing sideways, and shorter when facing north and south because of the perspective. At the same time, it would get wider when facing north and south, and less wide when facing right or left. I'd like to avoid actually drawing the aimer texture in 3d because I'm still using spritebatch's layerdepth parameter at this point in my project, and I don't want to have to figure out how to draw a 3d object within the depth sorting system I already have. I can provide code and more details if this is too vague as a question... This is my first post on stack exchange. Thanks a lot for reading! Note: (I think) I realize it can't be a technically correct 3D perspective, because the spritebatch's vector2 scaling argument doesn't allow for an object to be skewed the way it actually should be. What I'm really interested in is, is there a good way to fake the effect, or should I just drop it and not scale at all? Edit to clarify without the help of a picture (apparently I can't post them yet): I want the aimer arrow to look like it has been painted on the ground at the character's feet, so it should appear to be drawn on the ground plane (in my case the XZ plane) which should be tilted at a 45 degree angle (around the X axis) from the viewing perspective. Alex

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