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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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• Attaching two objects and changing their world matrices accordingly

  - by A-Type

  I'm having a hard time wrapping my head around the transformations required to bind two objects together in either a two-way or one-way relationship. I will need to implement both types. For the first case, I want to be able to 'couple' two ships together in space. The ships have different mass, of course. Forces applied to either ship will use combined mass and moment of inertia to calculate and move both ships. The trick is, being sure that the point at which they are coupled remains the same, and they don't move at all relative to each other. The second case is similar: I want a ship to be able to enter the atmosphere of a planet and move relative to the planet. The planet will be orbiting the sun, which is fixed at 0,0,0. Essentially, when the ship is sitting still outside of the atmosphere, the planet will move past it on its course-- but when the ship is sitting still inside the atmosphere, it moves and rotates with the planet, so that it is always relative to the horizon. Essentially, the vertices which make up the ship are now transformed just like the ones that make up the planet, except that the ship can move itself around relative to the planet. I get the feeling I can implement both of these with the same code. Essentially, I am thinking of giving each object (which I call Fixtures) a list of "slave" Fixtures onto which that Fixture's world matrix is imposed. So, this would be the planet imposing its world on any contained ships. In the case of coupling, I would simply make each ship a slave of the other, somehow. Obviously I can't just multiply the ship's world matrix by the planet's, or each ship by the others. What I'd like some help with is what calculations to make in order to get a nice, seamless relative world to the other object. I was thinking maybe I could just multiply the world of the slave by the inverse of the master, but then when you couple two ships you would lose all that world data. So, perhaps I need an intermediate "world" which is the absolute world, but use a secondary "final world" to actually transform the objects?

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• How to utilize miniMax algorrithm in Checkers game

  - by engineer

  I am sorry...as there are too many articles about it.But I can't simple get this. I am confused in the implementation of AI. I have generated all possible moves of computer's type pieces. Now I can't decide the flow. Whether I need to start a loop for the possible moves of each piece and assign score to it.... or something else is to be done. Kindly tell me the proper flow/algorithm for this. Thanks

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• Adjust sprite bounds of the visible part of texture

  - by Crazy D0G

  Is there any way to adjust the boundaries of the visible part of the sprite? To make it easier to understand: I have a texture, such as shown at figure 1. Then I break it into pieces and fill the resulting fragments using PRKit (wood texture on figure 2 and 3). But the resulting fragments have the transparent (green color on figure 2 and 3) and when creating a sprite from the fragments they have the size of the initial texture. Is there a way to get rid of this transparency and to adjust the size of the visible part (wood texture), openGL or cocos2d-x means? Maybe it help - draw() method from PRKit: void PRFilledPolygon::draw() { //CCNode::draw(); glDisableClientState(GL_COLOR_ARRAY); // we have a pointer to vertex points so enable client state glBindTexture(GL_TEXTURE_2D, texture->getName()); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_ONE_MINUS_SRC_ALPHA); glVertexPointer(2, GL_FLOAT, 0, areaTrianglePoints); glTexCoordPointer(2, GL_FLOAT, 0, textureCoordinates); glDrawArrays(GL_TRIANGLES, 0, areaTrianglePointCount); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); //Restore texture matrix and switch back to modelview matrix glEnableClientState(GL_COLOR_ARRAY);}

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• XNA ModelMesh.Draw vs GraphicsDevice.DrawIndexedPrimitives

  - by cubrman

  I am using XNA 4.0 and I wonder if drawing models with multiple meshes is better by filling the vertex and index buffers first and calling GraphicsDevice.DrawIndexedPrimitives() or by simply using good ol' foreach(...) {ModelMesh.Draw()}. Is it possible to add data to vertex/index buffers at all in order to pack all the models on the scene in them and then call Draw only once per frame? I would appreciate a link to an in-depth explanation. Thanks.

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• GLSL: Strange light reflections

  - by Tom

  According to this tutorial I'm trying to make a normal mapping using GLSL, but something is wrong and I can't find the solution. The output render is in this image: Image1 in this image is a plane with two triangles and each of it is different illuminated (that is bad). The plane has 6 vertices. In the upper left side of this plane are 2 identical vertices (same in the lower right). Here are some vectors same for each vertice: normal vector = 0, 1, 0 (red lines on image) tangent vector = 0, 0,-1 (green lines on image) bitangent vector = -1, 0, 0 (blue lines on image) here I have one question: The two identical vertices does need to have the same tangent and bitangent? I have tried to make other values to the tangents but the effect was still similar. Here are my shaders Vertex shader: #version 130 // Input vertex data, different for all executions of this shader. in vec3 vertexPosition_modelspace; in vec2 vertexUV; in vec3 vertexNormal_modelspace; in vec3 vertexTangent_modelspace; in vec3 vertexBitangent_modelspace; // Output data ; will be interpolated for each fragment. out vec2 UV; out vec3 Position_worldspace; out vec3 EyeDirection_cameraspace; out vec3 LightDirection_cameraspace; out vec3 LightDirection_tangentspace; out vec3 EyeDirection_tangentspace; // Values that stay constant for the whole mesh. uniform mat4 MVP; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // Position of the vertex, in worldspace : M * position Position_worldspace = (M * vec4(vertexPosition_modelspace,1)).xyz; // Vector that goes from the vertex to the camera, in camera space. // In camera space, the camera is at the origin (0,0,0). vec3 vertexPosition_cameraspace = ( V * M * vec4(vertexPosition_modelspace,1)).xyz; EyeDirection_cameraspace = vec3(0,0,0) - vertexPosition_cameraspace; // Vector that goes from the vertex to the light, in camera space. M is ommited because it's identity. vec3 LightPosition_cameraspace = ( V * vec4(LightPosition_worldspace,1)).xyz; LightDirection_cameraspace = LightPosition_cameraspace + EyeDirection_cameraspace; // UV of the vertex. No special space for this one. UV = vertexUV; // model to camera = ModelView vec3 vertexTangent_cameraspace = MV3x3 * vertexTangent_modelspace; vec3 vertexBitangent_cameraspace = MV3x3 * vertexBitangent_modelspace; vec3 vertexNormal_cameraspace = MV3x3 * vertexNormal_modelspace; mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); // You can use dot products instead of building this matrix and transposing it. See References for details. LightDirection_tangentspace = TBN * LightDirection_cameraspace; EyeDirection_tangentspace = TBN * EyeDirection_cameraspace; } Fragment shader: #version 130 // Interpolated values from the vertex shaders in vec2 UV; in vec3 Position_worldspace; in vec3 EyeDirection_cameraspace; in vec3 LightDirection_cameraspace; in vec3 LightDirection_tangentspace; in vec3 EyeDirection_tangentspace; // Ouput data out vec3 color; // Values that stay constant for the whole mesh. uniform sampler2D DiffuseTextureSampler; uniform sampler2D NormalTextureSampler; uniform sampler2D SpecularTextureSampler; uniform mat4 V; uniform mat4 M; uniform mat3 MV3x3; uniform vec3 LightPosition_worldspace; void main(){ // Light emission properties // You probably want to put them as uniforms vec3 LightColor = vec3(1,1,1); float LightPower = 40.0; // Material properties vec3 MaterialDiffuseColor = texture2D( DiffuseTextureSampler, vec2(UV.x,-UV.y) ).rgb; vec3 MaterialAmbientColor = vec3(0.1,0.1,0.1) * MaterialDiffuseColor; //vec3 MaterialSpecularColor = texture2D( SpecularTextureSampler, UV ).rgb * 0.3; vec3 MaterialSpecularColor = vec3(0.5,0.5,0.5); // Local normal, in tangent space. V tex coordinate is inverted because normal map is in TGA (not in DDS) for better quality vec3 TextureNormal_tangentspace = normalize(texture2D( NormalTextureSampler, vec2(UV.x,-UV.y) ).rgb*2.0 - 1.0); // Distance to the light float distance = length( LightPosition_worldspace - Position_worldspace ); // Normal of the computed fragment, in camera space vec3 n = TextureNormal_tangentspace; // Direction of the light (from the fragment to the light) vec3 l = normalize(LightDirection_tangentspace); // Cosine of the angle between the normal and the light direction, // clamped above 0 // - light is at the vertical of the triangle -> 1 // - light is perpendicular to the triangle -> 0 // - light is behind the triangle -> 0 float cosTheta = clamp( dot( n,l ), 0,1 ); // Eye vector (towards the camera) vec3 E = normalize(EyeDirection_tangentspace); // Direction in which the triangle reflects the light vec3 R = reflect(-l,n); // Cosine of the angle between the Eye vector and the Reflect vector, // clamped to 0 // - Looking into the reflection -> 1 // - Looking elsewhere -> < 1 float cosAlpha = clamp( dot( E,R ), 0,1 ); color = // Ambient : simulates indirect lighting MaterialAmbientColor + // Diffuse : "color" of the object MaterialDiffuseColor * LightColor * LightPower * cosTheta / (distance*distance) + // Specular : reflective highlight, like a mirror MaterialSpecularColor * LightColor * LightPower * pow(cosAlpha,5) / (distance*distance); //color.xyz = E; //color.xyz = LightDirection_tangentspace; //color.xyz = EyeDirection_tangentspace; } I have replaced the original color value by EyeDirection_tangentspace vector and then I got other strange effect but I can not link the image (not eunogh reputation) Is it possible that with this shaders is something wrong, or maybe in other place in my code e.g with my matrices? SOLVED Solved... 3 days needed for changing one letter from this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(12*sizeof(float)) // array buffer offset ); to this: glBindBuffer(GL_ARRAY_BUFFER, vbo); glVertexAttribPointer ( 4, // attribute 3, // size GL_FLOAT, // type GL_FALSE, // normalized? sizeof(VboVertex), // stride (void*)(11*sizeof(float)) // array buffer offset ); see difference? :)

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• Linear search vs Octree (Frustum cull)

  - by Dave

  I am wondering whether I should look into implementing an octree of some kind. I have a very simple game which consists of a 3d plane for the floor. There are multiple objects scattered around on the ground, each one has an aabb in world space. Currently I just do a loop through the list of all these objects and check if its bounding box intersects with the frustum, it works great but I am wondering if if it would be a good investment in an octree. I only have max 512 of these objects on the map and they all contain bounding boxes. I am not sure if an octree would make it faster since I have so little objects in the scene.

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• Alpha From PNGs Butchered

  - by ashes999

  I have a pretty vanilla Monogame game. I'm using PNG for all my sprites (made in Photoshop). I noticed that XNA is butchering the aliasing; no matter what I do, my graphics appear jaggedy. Below is a screenshot. The bottom half is what XNA shows me when I zoom in 2X using a Matrix on my GraphicsDevice (to make the effect more obvious). The top is when I pasted the same sprites from Photoshop and scaled them to 200%. Note that partially transparent pixels are turning whiteish. Is there a way to fix this? What am I doing wrong? Here's the relevant call to draw to the SpriteBatch: spriteBatch.Draw(this.texture, this.positionVector, null, Color.White, this.Angle, this.originVector, 1f, SpriteEffects.None, 0f); (this.positionVector can easily be Vector.Zero; Color.White as 100% alpha, I think; this.Angle can be a real angle (small > in the image) or zero (the orb itself).

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• How does a collision engine work?

  - by JXPheonix

  Original question: Click me How exactly does a collision engine work? This is an extremely broad question. What code keeps things bouncing against each other, what code makes the player walk into a wall instead of walk through the wall? How does the code constantly refresh the players position and objects position to keep gravity and collision working as it should? If you don't know what a collision engine is, basically it's generally used in platform games to make the player acutally hit walls and the like. There's the 2D type and the 3D type, but they all accomplish the same thing: collision. So, what keeps a collision engine ticking?

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• Any way to set up a grid for a board game in cocos 2d?

  - by Scott

  My first idea was to create a 2d array for my columns and rows, but it seems like there should be a better, or possibly cleaner, way to achieve this. Each square on the grid is going to have a background image, probably a .png although I might just draw the images with a draw method. Basically, I want to be able to drag and drop images onto the individual grid squares. I've been searching for a solution and the closest thing I can find is the tiled map solution. That just seems like a little overkill for what I'm trying to accomplish. Also, I don't know if this helps but i need my grid to be 12 by 12 and take up the entire width of the iphone screen.

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• How do you get the total asset size (or total resource size) in an Android game?

  - by tom_mai78101

  In an Android Java project, there are two folders, asset and res. To me, I usually put some stuffs, like PNG files, sound files, etc. in either one of the two folder. When resources are increasingly becoming more and more in those folders, the time it takes to load them will increase. Therefore, a loading screen is a must in these situation. The total size is to be used in a loading screen, so that I can guess the average time it takes to load each resources, from 0 bytes to its individual resource file size. I only know that by adding all individual sizes in a respective order, I will then obtain the total asset or res folder size, simply by adding them up. So, when it comes to getting the total file size from either folder, how do you obtain their individual resource/object sizes, respectively? Thanks in advance.

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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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• Publishing a game -- any way to target both WP7 and Win8 Store?

  - by Rei Miyasaka

  I'm at a dilemma which seems should soon become an important issue for a lot of developers. If I build a game in XNA, I won't be able to publish it on the Windows 8 Store, as it would be a classic application -- and classic applications can't be sold on the store. If I build a game in Metro DirectX, I would be able to sell it on the Store, but porting it to Windows Phone would involve porting it to Reach XNA, which in fact would likely involve more effort even than porting to OS X or Android -- both of which support C++. Of all the WinRT API that is supported on C++/JS/.NET, DirectX can only be programmed from C++. It's also unlikely that Microsoft will update Windows 7 or Vista to support the new DirectX features, although that would make the Metro DirectX the first new version of DirectX to stop supporting the immediate predecessor OS. If I build a game in Pre-Win8 DirectX 9/10/11, I won't be able to sell it on the Windows Store or Windows Phone, but I could sell it on something like Steam. It would also involve the most amount of manual plumbing. In fact, DirectWrite, despite being part of DirectX 11, doesn't talk to Direct3D. I'm getting really tired of all these restrictions -- artificial and otherwise -- and I'm coming to a point where I'm considering switching to a platform with a less fragmented API, like Android or Mac/iOS. As far as bringing a game into market goes, excluding the actual market share of any platforms that I might consider, what other factors would help me in making a decision? Just a few years ago this question was a lot easier to answer: if you were primarily concerned with Windows platforms, all you had to answer was whether you wanted DirectX, XNA, or something like SlimDX. If you made the wrong decision, no biggie -- all you really would have lost is XBox and the fairly small Windows Phone market.

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• How do I keep a 3D model on the screen in OpenGL?

  - by NoobScratcher

  I'm trying to keep a 3D model on the screen by placing my glDrawElement functions inside the draw function with the declarations at the top of .cpp. When I render the model, the model attaches it self to the current vertex buffer object. This is because my whole graphical user interface is in 2D quads except the window frame. Is there a way to avoid this from happening? or any common causes of this? Creating the file object: int index = IndexAssigner(1, 1); //make a fileobject and store list and the index of that list in a c string ifstream file (list[index].c_str() ); //Make another string //string line; points.push_back(Point()); Point p; int face[4]; Model rendering code: int numfloats = 4; float* point=reinterpret_cast<float*>(&points[0]); int num_bytes=numfloats*sizeof(float); cout << "Size Of Point" << sizeof(Point) << endl; GLuint vertexbuffer; glGenVertexArrays(1, &vao[3]); glGenBuffers(1, &vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, points.size()*sizeof(points), points.data(), GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, num_bytes, &points[0]); glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(3, GL_FLOAT, points.size(), &points[0]); glEnableClientState(GL_INDEX_ARRAY); glIndexPointer(GL_FLOAT, faces.size(), faces.data()); glEnableVertexAttribArray(0); glDrawElements(GL_QUADS, points.size(), GL_UNSIGNED_INT, points.data()); glDrawElements(GL_QUADS, faces.size(), GL_UNSIGNED_INT, faces.data());

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• 2D Tile based Game Collision problem

  - by iNbdy

  I've been trying to program a tile based game, and I'm stuck at the collision detection. Here is my code (not the best ^^): void checkTile(Character *c, int **map) { int x1,x2,y1,y2; /* Character position in the map */ c->upY = (c->y) / TILE_SIZE; // Top left corner c->downY = (c->y + c->h) / TILE_SIZE; // Bottom left corner c->leftX = (c->x) / TILE_SIZE; // Top right corner c->rightX = (c->x + c->w) / TILE_SIZE; // Bottom right corner x1 = (c->x + 10) / TILE_SIZE; // 10px from left side point x2 = (c->x + c->w - 10) / TILE_SIZE; // 10px from right side point y1 = (c->y + 10) / TILE_SIZE; // 10px from top side point y2 = (c->y + c->h - 10) / TILE_SIZE; // 10px from bottom side point /* Top */ if (map[c->upY][x1] > 2 || map[c->upY][x2] > 2) c->topCollision = 1; else c->topCollision = 0; /* Bottom */ if ((map[c->downY][x1] > 2 || map[c->downY][x2] > 2)) c->downCollision = 1; else c->downCollision = 0; /* Left */ if (map[y1][c->leftX] > 2 || map[y2][c->leftX] > 2) c->leftCollision = 1; else c->leftCollision = 0; /* Right */ if (map[y1][c->rightX] > 2 || map[y2][c->rightX] > 2) c->rightCollision = 1; else c->rightCollision = 0; } That calculates 8 collision points My moving function is like that: void movePlayer(Character *c, int **map) { if ((c->dirX == LEFT && !c->leftCollision) || (c->dirX == RIGHT && !c->rightCollision)) c->x += c->vx; if ((c->dirY == UP && !c->topCollision) || (c->dirY == DOWN && !c->downCollision)) c->y += c->vy; checkPosition(c, map); } and the checkPosition: void checkPosition(Character *c, int **map) { checkTile(c, map); if (c->downCollision) { if (c->state != JUMPING) { c->vy = 0; c->y = (c->downY * TILE_SIZE - c->h); } } if (c->leftCollision) { c->vx = 0; c->x = (c->leftX) * TILE_SIZE + TILE_SIZE; } if (c->rightCollision) { c->vx = 0; c->x = c->rightX * TILE_SIZE - c->w; } } This works, but sometimes, when the player is landing on ground, right and left collision points become equal to 1. So it's as if there were collision coming from left or right. Does anyone know why this is doing this?

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• Help understand GLSL directional light on iOS (left handed coord system)

  - by Robse

  I now have changed from GLKBaseEffect to a own shader implementation. I have a shader management, which compiles and applies a shader to the right time and does some shader setup like lights. Please have a look at my vertex shader code. Now, light direction should be provided in eye space, but I think there is something I don't get right. After I setup my view with camera I save a lightMatrix to transform the light from global space to eye space. My modelview and projection setup: - (void)setupViewWithWidth:(int)width height:(int)height camera:(N3DCamera *)aCamera { aCamera.aspect = (float)width / (float)height; float aspect = aCamera.aspect; float far = aCamera.far; float near = aCamera.near; float vFOV = aCamera.fieldOfView; float top = near * tanf(M_PI * vFOV / 360.0f); float bottom = -top; float right = aspect * top; float left = -right; // projection GLKMatrixStackLoadMatrix4(projectionStack, GLKMatrix4MakeFrustum(left, right, bottom, top, near, far)); // identity modelview GLKMatrixStackLoadMatrix4(modelviewStack, GLKMatrix4Identity); // switch to left handed coord system (forward = z+) GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeScale(1, 1, -1)); // transform camera GLKMatrixStackMultiplyMatrix4(modelviewStack, GLKMatrix4MakeWithMatrix3(GLKMatrix3Transpose(aCamera.orientation))); GLKMatrixStackTranslate(modelviewStack, -aCamera.position.x, -aCamera.position.y, -aCamera.position.z); } - (GLKMatrix4)modelviewMatrix { return GLKMatrixStackGetMatrix4(modelviewStack); } - (GLKMatrix4)projectionMatrix { return GLKMatrixStackGetMatrix4(projectionStack); } - (GLKMatrix4)modelviewProjectionMatrix { return GLKMatrix4Multiply([self projectionMatrix], [self modelviewMatrix]); } - (GLKMatrix3)normalMatrix { return GLKMatrix3InvertAndTranspose(GLKMatrix4GetMatrix3([self modelviewProjectionMatrix]), NULL); } After that, I save the lightMatrix like this: [self.renderer setupViewWithWidth:view.drawableWidth height:view.drawableHeight camera:self.camera]; self.lightMatrix = [self.renderer modelviewProjectionMatrix]; And just before I render a 3d entity of the scene graph, I setup the light config for its shader with the lightMatrix like this: - (N3DLight)transformedLight:(N3DLight)light transformation:(GLKMatrix4)matrix { N3DLight transformedLight = N3DLightMakeDisabled(); if (N3DLightIsDirectional(light)) { GLKVector3 direction = GLKVector3MakeWithArray(GLKMatrix4MultiplyVector4(matrix, light.position).v); direction = GLKVector3Negate(direction); // HACK -> TODO: get lightMatrix right! transformedLight = N3DLightMakeDirectional(direction, light.diffuse, light.specular); } else { ... } return transformedLight; } You see the line, where I negate the direction!? I can't explain why I need to do that, but if I do, the lights are correct as far as I can tell. Please help me, to get rid of the hack. I'am scared that this has something to do, with my switch to left handed coord system. My vertex shader looks like this: attribute highp vec4 inPosition; attribute lowp vec4 inNormal; ... uniform highp mat4 MVP; uniform highp mat4 MV; uniform lowp mat3 N; uniform lowp vec4 constantColor; uniform lowp vec4 ambient; uniform lowp vec4 light0Position; uniform lowp vec4 light0Diffuse; uniform lowp vec4 light0Specular; varying lowp vec4 vColor; varying lowp vec3 vTexCoord0; vec4 calcDirectional(vec3 dir, vec4 diffuse, vec4 specular, vec3 normal) { float NdotL = max(dot(normal, dir), 0.0); return NdotL * diffuse; } ... vec4 calcLight(vec4 pos, vec4 diffuse, vec4 specular, vec3 normal) { if (pos.w == 0.0) { // Directional Light return calcDirectional(normalize(pos.xyz), diffuse, specular, normal); } else { ... } } void main(void) { // position highp vec4 position = MVP * inPosition; gl_Position = position; // normal lowp vec3 normal = inNormal.xyz / inNormal.w; normal = N * normal; normal = normalize(normal); // colors vColor = constantColor * ambient; // add lights vColor += calcLight(light0Position, light0Diffuse, light0Specular, normal); ... }

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• Java : 2D Collision Detection

  - by neko

  I'm been working on 2D rectangle collision for weeks and still cannot get this problem fixed. The problem I'm having is how to adjust a player to obstacles when it collides. I'm referencing this link. The player sometime does not get adjusted to obstacles. Also, it sometimes stuck in obstacle guy after colliding. Here, the player and the obstacle are inheriting super class Sprite I can detect collision between the two rectangles and the point by ; public Point getSpriteCollision(Sprite sprite, double newX, double newY) { // set each rectangle Rectangle spriteRectA = new Rectangle( (int)getPosX(), (int)getPosY(), getWidth(), getHeight()); Rectangle spriteRectB = new Rectangle( (int)sprite.getPosX(), (int)sprite.getPosY(), sprite.getWidth(), sprite.getHeight()); // if a sprite is colliding with the other sprite if (spriteRectA.intersects(spriteRectB)){ System.out.println("Colliding"); return new Point((int)getPosX(), (int)getPosY()); } return null; } and to adjust sprites after a collision: // Update the sprite's conditions public void update() { // only the player is moving for simplicity // collision detection on x-axis (just x-axis collision detection at this moment) double newX = x + vx; // calculate the x-coordinate of sprite move Point sprite = getSpriteCollision(map.getSprite().get(1), newX, y);// collision coordinates (x,y) if (sprite == null) { // if the player is no colliding with obstacle guy x = newX; // move } else { // if collided if (vx > 0) { // if the player was moving from left to right x = (sprite.x - vx); // this works but a bit strange } else if (vx < 0) { x = (sprite.x + vx); // there's something wrong with this too } } vx=0; y+=vy; vy=0; } I think there is something wrong in update() but cannot fix it. Now I only have a collision with the player and an obstacle guy but in future, I'm planning to have more of them and making them all collide with each other. What would be a good way to do it? Thanks in advance.

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• how to modify shadow mapping in "3D Graphics with XNA Game Studio 4.0"?

  - by naprox

  So I've been following the tutorials from the book Sean James's "3D Graphics with XNA Game Studio 4.0", and have been doing fine until i reached the shadow mapping part. in this book it creates point lights with a Sphere model. my first Q is how to draw a directional Light with this frame work? secondly it can do shadow mapping just for one light, how can i do shadow mapping for all or parts of the lights in the game? i just want to know how to modify this codes to do the above tasks. I've followed tutorials on MSDN and some other sites and didn't got the answer. please help me, its so urgent. and if any one wants, the complete code is here: http://www.mediafire.com/?6ct11mc1g8f891h

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• How do I implement layers on a tile map?

  - by mitch

  I have a game where, based upon the visible tiles in the viewport, I need to retrieve data of items in the visible tiles. I am planning to use Javascript to AJAX request in a batch based upon the visible tiles which contain image tags like Google Maps. The layer will be in SVG or canvas. The item information will be in JSON format. What is the best approach, to fetch the data? I currently have complex class I wrote in Javascript which determines the visible columns/rows and offsets relative to the visible area shown. Each item is also user contributed and will be rendered in canvas or SVG layer.

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• XNA 4.0 Refresh AudioEngine, WaveBank and Others Not Found

  - by Peteyslatts

  I'm going through the Learning XNA 4.0 book, and unfortunately I installed XNA 4.0 refresh. All the code up until now has worked, with the exception of me needing to remove the Framework.Net and Framework.Storage. (As a side question, will this be problematic later?) The problem I'm having now is that in my Game1.cs file, I have imported all of the XNA.Framework libraries, and when I try and create instances of any of the following classes, an error pops up saying VisualStudio can't find them: AudiEngine, WaveBank, SoundBank, and Cue. I have googled around for a while, and the only solution I saw was to import Microsoft.Xna.Framework.Xact, but this doesn't seem to exist for me. Any help is much appreciated, Thanks Peter.

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• How to export Oracle statistics

  - by A_M

  Hi, I am writing some new SQL queries and want to check the query plans that the Oracle query optimiser would come up with in production. My development database doesn't have anything like the data volumes of the production database. How can I export database statistics from a production database and re-import them into a development database? I don't have access to the production database, so I can't simply generate explain plans on production without going through a third party hosting organisation. This is painful. So I want a local database which is in some way representative of production on which I can try out different things. Also, this is for a legacy application. I'd like to "improve" the schema, by adding appropriate indexes. constraints, etc. I need to do this in my development database first, before rolling out to test and production. If I add an index and re-generate statistics in development, then the statistics will be generated around the development data volumes, which makes it difficult to assess the impact my changes on production. Does anyone have any tips on how to deal with this? Or is it just a case of fixing unexpected behaviour once we've discovered it on production? I do have a staging database with production volumes, but again I have to go through a third party to run queries against this, which is painful. So I'm looking for ways to cut out the middle man as much as possible. All this is using Oracle 9i. Thanks.

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• How to make an Actor follow my finger

  - by user48352

  I'm back with another question that may be really simple. I've a texture drawn on my spritebatch and I'm making it move up or down (y-axis only) with Libgdx's Input Handler: touchDown and touchUp. @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { myWhale.touchDownY = screenY; myWhale.isTouched = true; return true; } @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { myWhale.isTouched = false; return false; } myWhale is an object from Whale Class where I move my texture position: public void update(float delta) { this.delta = delta; if(isTouched){ dragWhale(); } } public void dragWhale() { if(Gdx.input.getY(0) - touchDownY < 0){ if(Gdx.input.getY(0)<position.y+height/2){ position.y = position.y - velocidad*delta; } } else{ if(Gdx.input.getY(0)>position.y+height/2){ position.y = position.y + velocidad*delta; } } } So the object moves to the center of the position where the person is pressing his/her finger and most of the time it works fine but the object seems to take about half a second to move up or down and sometimes when I press my finger it wont move. Maybe there's another simplier way to do this. I'd highly appreciate if someone points me on the right direction.

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

  - by jessejuicer

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

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• Frame Independent Movement

  - by ShrimpCrackers

  I've read two other threads here on movement: Time based movement Vs Frame rate based movement?, and Fixed time step vs Variable time step but I think I'm lacking a basic understanding of frame independent movement because I don't understand what either of those threads are talking about. I'm following along with lazyfoo's SDL tutorials and came upon the frame independent lesson. http://lazyfoo.net/SDL_tutorials/lesson32/index.php I'm not sure what the movement part of the code is trying to say but I think it's this (please correct me if I'm wrong): In order to have frame independent movement, we need to find out how far an object (ex. sprite) moves within a certain time frame, for example 1 second. If the dot moves at 200 pixels per second, then I need to calculate how much it moves within that second by multiplying 200 pps by 1/1000 of a second. Is that right? The lesson says: "velocity in pixels per second * time since last frame in seconds. So if the program runs at 200 frames per second: 200 pps * 1/200 seconds = 1 pixel" But...I thought we were multiplying 200 pps by 1/1000th of a second. What is this business with frames per second? I'd appreciate if someone could give me a little bit more detailed explanation as to how frame independent movement works. Thank you.

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• What economic books would you suggest for learning about economic valuation of goods and simulations thereof?

  - by Rushyo

  I'm looking to create an economic model for a game based on goods created procedurally. Every natural resource and produced good would be procedurally generated, with certain goods being assigned certain uses. Fakesium might be used for the production of Weapon A and produced from Fakesium factories which use Dilithium and Widgets as reagents, where Widgets are also the product of Foo and Bar The problem is not creating the resources and their various production utlities - but getting the game's AI empires and merchants to (Addendum: somewhat) correctly value the goods according to their scarcity, utility and production costs. I need to create a simulation of goods which allows the various game factions to assign a common value denominator (credits) to each resource, depending on how much its worth to that empire. I see the simulation being something like: "I have a high requirement for Weapon A. Since I don't have much of Fakesium, which is needed for Weapon A - I must have a high demand for Fakesium. If I can acquire Fakesium, devalue it. If not, increase its value - and also increase demand for Dilithium and Widgets too." This is very naive - because it may be much much cheaper for the empire to simply purchase Dilithium and Widgets directly rather than purchasing Fakesium, for example. Another example is two resources might allow the creation of Weapon A (Fakesium and Lieron), so we'd need to consider that. I've been scratching my head over the problem and it keeps growing. By the time the player joins the world, I'd expect enough iterations of this process to have occurred that prices would have largely normalised - and would then only trigger rarely to compensate for major changes (eg. if the player blows up the world's only Foo mine!) Could anyone suggest resources (books, largely) which outline this style of modelling, preferably in the context of simulations? Since this problem would never occur outside fantasy worlds, I figured this is probably the most likely place to find people who have encountered similar problems and I'm sure there's people who know of good places for Games Developers to start looking at less specific economic theory too. Additionally, does anyone know of any developers with blogs whose games or research applications perform similar modelling? EDIT: I think I should underline that I'm not looking for optimal solutions. I'm looking to make the actors impulsive - making rudimentary decisions based on fuzzy inputs about what they care about or don't. I'm aiming to understand the problem area better not derive answers. All the textbooks I've found seem to be about real-world economics or how to solve complex theoretical problems, neither of which are terribly relevant to the actor's decision making.

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