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  • Triangulating a partially triangulated mesh (2D)

    - by teodron
    Referring to the above exhibits, this is the scenario I am working with: starting with a planar graph (in my case, a 2D mesh) with a given triangulation, based on a certain criterion, the graph nodes are labeled as RED and BLACK. (A) a subgraph containing all the RED nodes (with edges between only the directly connected neighbours) is formed (note: although this figure shows a tree forming, it may well happen that the subgraph contain loops) (B) Problem: I need to quickly build a triangulation around the subgraph (e.g. as shown in figure C), but under the constraint that I have to keep the already present edges in the final result. Question: Is there a fast way of achieving this given a partially triangulated mesh? Ideally, the complexity should be in the O(n) class. Some side-remarks: it would be nice for the triangulation algorithm to take into account a certain vertex priority when adding edges (e.g. it should always try to build a "1-ring" structure around the most important nodes first - I can implement iteratively such a routine, but it's O(n^2) ). it would also be nice to reflect somehow the "hop distance" when adding edges: add edges first between the nodes that were "closer" to each other given the start topology. Nevertheless, disregarding the remarks, is there an already known scenario similar to this one where a triangulation is built upon a partially given set of triangles/edges?

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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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  • Lighting with VBO

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

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  • Build a view frustum from angles

    - by MulletDevil
    I have 4 angles, left, right, top & bottom. These angles are in degrees. They define the angle between the forward vector and the corresponding side. I am trying to use these to calculate the required values for Perseective Off Centre function found here http://docs.unity3d.com/Documentation/ScriptReference/Camera-projectionMatrix.html I tried doing (near plane-far plane) * Tan(angle) But that didn't give the correct results.

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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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  • Debugging Minimum Translation Vector

    - by SyntheCypher
    I implemented the minimum translation vector from codezealot's tutorial on SAT (Separating Axis Theorem) but I'm having an issue I can't quite figure out. Here's the example I have: As you can see in top and bottom left images regardless of the side the of the green car which red car is penetrating the MTV for the red car still remains as a negative number also here is the same example when the front of the red car is facing the opposite direction the number will always be positive. When the red car is past the half way through the green car it should switch polarity. I thought I'd compensated for this in my code, but apparently not either that or it's a bug I can find. Here is my function for finding and returning the MTV, any help would be much appreciated: Code

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  • GLSL Normals not transforming propertly

    - by instancedName
    I've been stuck on this problem for two days. I've read many articles about transforming normals, but I'm just totaly stuck. I understand choping off W component for "turning off" translation, and doing inverse/traspose transformation for non-uniform scaling problem, but my bug seems to be from a different source. So, I've imported a simple ball into OpenGL. Only transformation that I'm applying is rotation over time. But when my ball rotates, the illuminated part of the ball moves around just as it would if direction light direction was changing. I just can't figure out what is the problem. Can anyone help me with this? Here's the GLSL code: Vertex Shader: #version 440 core uniform mat4 World, View, Projection; layout(location = 0) in vec3 VertexPosition; layout(location = 1) in vec3 VertexColor; layout(location = 2) in vec3 VertexNormal; out vec4 Color; out vec3 Normal; void main() { Color = vec4(VertexColor, 1.0); vec4 n = World * vec4(VertexNormal, 0.0f); Normal = n.xyz; gl_Position = Projection * View * World * vec4(VertexPosition, 1.0); } Fragment Shader: #version 440 core uniform vec3 LightDirection = vec3(0.0, 0.0, -1.0); uniform vec3 LightColor = vec3(1f); in vec4 Color; in vec3 Normal; out vec4 FragColor; void main() { diffuse = max(0.0, dot(normalize(-LightDirection), normalize(Normal))); vec4 scatteredLight = vec4(LightColor * diffuse, 1.0f); FragColor = min(Color * scatteredLight, vec4(1.0)); }

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  • What is the purpose of bitdepth for the several components of the framebuffer in glfwWindowHint function of GLFW3?

    - by Rui d'Orey
    I would like to know what are the following "framebuffer related hints" of GLFW3 function glfwWindowHint : GLFW_RED_BITS GLFW_GREEN_BITS GLFW_BLUE_BITS GLFW_ALPHA_BITS GLFW_DEPTH_BITS GLFW_STENCIL_BITS What is the purpose of this? Usually their default values are enough? Where are those bits stored? In a buffer in the GPU? What do they affect? And by that I mean in what way Thank you in advance!

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  • Outline Shader Effect for Orthogonal Geometry in XNA

    - by Griffin
    I just recently started learning the art of shading, but I can't give an outline width to 2D, concave geometry when restrained to a single vertex/pixel shader technique (thanks to XNA). the shape I need to give an outline to has smooth, per-vertex coloring, as well as opacity. The outline, which has smooth, per-vertex coloring, variable width, and opacity cannot interfere with the original shape's colors. A pixel depth border detection algorithm won't work because pixel depth isn't a 3.0 semantic. expanding geometry / redrawing won't work because it interferes with the original shape's colors. I'm wondering if I can do something with the stencil/depth buffer outside of the shader functions since I have access to that through the graphics device. But I don't believe I'm able to manipulate actual values. How might I do this?

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  • Render angles of a 3D model into 2D images?

    - by Ricket
    Is there a tool out there that you can give a 3D model file, and it will output 2D renders of it from various angles? For example if you were making a 2D RPG but you want to make your character look nice, you might make the character in 3D and then just render the character from 8 or more angles into images which then are used by the 2D engine to give a pseudo-3D look. Does such a tool exist or will it need to be custom-written or done manually?

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  • OpenGL error LNK2019

    - by Ghilliedrone
    I'm trying to compile a basic OpenGL program. I linked opengl32.lib and glu32.lib but I'm getting errors. The errors I get are: error LNK1120: 7 unresolved externals error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup error LNK2019: unresolved external symbol "public: float __thiscall GLWindow::getElapsedSeconds(void)" (?getElapsedSeconds@GLWindow@@QAEMXZ) referenced in function _WinMain@16 error LNK2019: unresolved external symbol "public: bool __thiscall GLWindow::isRunning(void)" (?isRunning@GLWindow@@QAE_NXZ) referenced in function _WinMain@16 error LNK2019: unresolved external symbol "public: void __thiscall GLWindow::attachExample(class Example *)" (?attachExample@GLWindow@@QAEXPAVExample@@@Z) referenced in function _WinMain@16 error LNK2019: unresolved external symbol "public: void __thiscall GLWindow::destroy(void)" (?destroy@GLWindow@@QAEXXZ) referenced in function _WinMain@16 error LNK2019: unresolved external symbol "public: __thiscall GLWindow::GLWindow(struct HINSTANCE__ *)" (??0GLWindow@@QAE@PAUHINSTANCE__@@@Z) referenced in function _WinMain@16 error LNK2019: unresolved external symbol "private: void __thiscall GLWindow::setupPixelFormat(void)" (?setupPixelFormat@GLWindow@@AAEXXZ) referenced in function "public: long __stdcall GLWindow::WndProc(struct HWND__ *,unsigned int,unsigned int,long)" (?WndProc@GLWindow@@QAGJPAUHWND__@@IIJ@Z)

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  • backface culling error

    - by acrilige
    I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation. (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason?

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  • OpenGL ES 2. How do I Create a Basic Fading Streak Effect?

    - by dugla
    For the iPad app I am writing using OpenGL ES 2 I have a single quad - shaded using GLSL - that is dragged around the screen. Very basic. This works fine. But is rather boring. I want to increase the coolness a bit in the following way: when the user drags the quad it leaves a streak behind that fades over time. Continuous dragging would be a bit like a streaking comet across the night sky. What is the simplest way to implement this? Thanks.

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  • Per-pixel collision detection - why does XNA transform matrix return NaN when adding scaling?

    - by JasperS
    I looked at the TransformCollision sample on MSDN and added the Matrix.CreateTranslation part to a property in my collision detection code but I wanted to add scaling. The code works fine when I leave scaling commented out but when I add it and then do a Matrix.Invert() on the created translation matrix the result is NaN ({NaN,NaN,NaN},{NaN,NaN,NaN},...) Can anyone tell me why this is happening please? Here's the code from the sample: // Build the block's transform Matrix blockTransform = Matrix.CreateTranslation(new Vector3(-blockOrigin, 0.0f)) * // Matrix.CreateScale(block.Scale) * would go here Matrix.CreateRotationZ(blocks[i].Rotation) * Matrix.CreateTranslation(new Vector3(blocks[i].Position, 0.0f)); public static bool IntersectPixels( Matrix transformA, int widthA, int heightA, Color[] dataA, Matrix transformB, int widthB, int heightB, Color[] dataB) { // Calculate a matrix which transforms from A's local space into // world space and then into B's local space Matrix transformAToB = transformA * Matrix.Invert(transformB); // When a point moves in A's local space, it moves in B's local space with a // fixed direction and distance proportional to the movement in A. // This algorithm steps through A one pixel at a time along A's X and Y axes // Calculate the analogous steps in B: Vector2 stepX = Vector2.TransformNormal(Vector2.UnitX, transformAToB); Vector2 stepY = Vector2.TransformNormal(Vector2.UnitY, transformAToB); // Calculate the top left corner of A in B's local space // This variable will be reused to keep track of the start of each row Vector2 yPosInB = Vector2.Transform(Vector2.Zero, transformAToB); // For each row of pixels in A for (int yA = 0; yA < heightA; yA++) { // Start at the beginning of the row Vector2 posInB = yPosInB; // For each pixel in this row for (int xA = 0; xA < widthA; xA++) { // Round to the nearest pixel int xB = (int)Math.Round(posInB.X); int yB = (int)Math.Round(posInB.Y); // If the pixel lies within the bounds of B if (0 <= xB && xB < widthB && 0 <= yB && yB < heightB) { // Get the colors of the overlapping pixels Color colorA = dataA[xA + yA * widthA]; Color colorB = dataB[xB + yB * widthB]; // If both pixels are not completely transparent, if (colorA.A != 0 && colorB.A != 0) { // then an intersection has been found return true; } } // Move to the next pixel in the row posInB += stepX; } // Move to the next row yPosInB += stepY; } // No intersection found return false; }

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  • How to improve Minecraft-esque voxel world performance?

    - by SomeXnaChump
    After playing Minecraft I marveled a bit at its large worlds but at the same time I found them extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume Minecraft is fairly slow because: A) It's written in Java, and as most of the spatial partitioning and memory management activities happen in there, it would naturally be slower than a native C++ version. B) It doesn't partition its world very well. I could be wrong on both assumptions; however it got me thinking about the best way to manage large voxel worlds. As it is a true 3D world, where a block can exist in any part of the world, it is basically a big 3D array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc.) Now, I am assuming to make this sort of world perform well you would need to: A) Use a tree of some variety (oct/kd/bsp) to split all the cubes out; it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. B) Use some algorithm to work out which blocks can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. C) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees. I guess there is no right answer to this, but I would be interested to see peoples' opinions on the subject. How would you improve performance in a large voxel-based world?

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  • Strange behavior of RigidBody with gravity and impulse applied

    - by Heisenbug
    I'm doing some experiments trying to figure out how physics works in Unity. I created a cube mesh with a BoxCollider and a RigidBody. The cuve is laying on a mesh plane with a BoxCollider. I'm trying to update the object position applying a force on its RigidBody. Inside script FixedUpdate function I'm doing the following: public void FixedUpdate() { if (leftButtonPressed()) this.rigidbody.AddForce( this.transform.forward * this.forceStrength, ForceMode.Impulse); } Despite the object is aligned with the world axis and the force is applied along Z axis, it performs a quite big rotation movement around its y axis. Since I didn't modify the center of mass and the BoxCollider position and dimension, all values should be fine. Removing gravity and letting the object flying without touching the plane, the problem doesn't show. So I suppose it's related to the friction between objects, but I can't understand exactly which is the problem. Why this? What's my mistake? How can I fix this, or what's the right way to do such a moving an object on a plane through a force impulse?

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  • What is a good practice for 2D scene graph partitioning for culling?

    - by DevilWithin
    I need to know an efficient way to cull the scene graph objects, to render exclusively the ones in the view, and as fast as possible. I am thinking of doing it the following way, having in each object a local boundingbox which holds the object bounds, and a global boundingbox which holds the bounds of the object and all children. When a camera is moved, the render list is updated by traversing the global boundingboxes. When only the object is being moved, it tries to enlarge or shrink the ancestors global boundingboxes, and in the end updating or not the renderlist. What do you think of this approach? Do you think it will provide a fast and efficient culling? Also, because the render list is a contiguous list, it could accelerate the rendering, right? Any further tips for a 2D scene graphs are highly appreciated!

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  • Move the location of the XYZ pivot point on a mesh in UDK

    - by WebDevHobo
    When working with any mesh, you get an XYZ point somewhere on it. If you just want to move the mesh in any direction, it doesn't matter where this point is located. However, I want to rotate a door. This requires the point of rotation to be very specific. I can't find anywhere how to change the location of the point. Can anyone help? EDIT: solved, to change the pivot point, right click on the mesh, go to "Pivot" and move it. Then right click again and this time select "Save PrePivot to Pivot"

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  • How to attach an object to a rotating circle?

    - by armands
    I am trying to make an object get attached on a collision point to a circle that is rotating, but the player needs to get attached with a constant point on the player. For example the player is moving back and forth and when the user touches the screen and the player jumps up but what I need is that when the player collides with the circle it attaches it's legs to it and continues rotating with the circle. So I wanted to know how to make this kind of collision joint in Cocos2d Box2d?

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  • Creating a 2D Line Branch

    - by Danran
    I'm looking into creating a 2D line branch, something for a "lightning effect". I did ask this question before on creating a "lightning effect" (mainly though referring to the process of the glow & after effects the lightning has & to whether it was a good method to use or not); Methods of Creating a "Lightning" effect in 2D However i never did get around to getting it working. So i've been trying today to get a seconded attempt going but i'm getting now-were :/. So to be clear on what i'm trying to-do, in this article posted; http://drilian.com/2009/02/25/lightning-bolts/ I'm trying to create the line segments seen in the images on the site. I'm confused mainly by this line in the pseudo code; // Offset the midpoint by a random amount along the normal. midPoint += Perpendicular(Normalize(endPoint-startPoint))*RandomFloat(-offsetAmount,offsetAmount); If someone could explain this to me it would be really grateful :).

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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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  • Parenting Opengl with Groups in LibGDX

    - by Rudy_TM
    I am trying to make an object child of a Group, but this object has a draw method that calls opengl to draw in the screen. Its class its this public class OpenGLSquare extends Actor { private static final ImmediateModeRenderer renderer = new ImmediateModeRenderer10(); private static Matrix4 matrix = null; private static Vector2 temp = new Vector2(); public static void setMatrix4(Matrix4 mat) { matrix = mat; } @Override public void draw(SpriteBatch batch, float arg1) { // TODO Auto-generated method stub renderer.begin(matrix, GL10.GL_TRIANGLES); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.end(); } } In my screen class I have this, i call it in the constructor MyGroupClass spriteLab = new MyGroupClass(spriteSheetLab); OpenGLSquare square = new OpenGLSquare(); square.setX0(100); square.setY0(200); square.setX1(400); square.setY1(280); square.color.set(Color.BLUE); square.setSize(); //spriteLab.addActorAt(0, clock); spriteLab.addActor(square); stage.addActor(spriteLab); And the render in the screen I have @Override public void render(float arg0) { this.gl.glClear(GL10.GL_COLOR_BUFFER_BIT |GL10.GL_DEPTH_BUFFER_BIT); stage.draw(); stage.act(Gdx.graphics.getDeltaTime()); } The problem its that when i use opengl with parent, it resets all the other chldren to position 0,0 and the opengl renderer paints the square in the exact position of the screen and not relative to the parent. I tried using batch.enableBlending() and batch.disableBlending() that fixes the position problem of the other children, but not the relative position of the opengl drawing and it also puts alpha to the glDrawing. What am i doing wrong?:/

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  • Triangle Picking Picking Back faces

    - by Tangeleno
    I'm having a bit of trouble with 3D picking, at first I thought my ray was inaccurate but it turns out that the picking is happening on faces facing the camera and faces facing away from the camera which I'm currently culling. Here's my ray creation code, I'm pretty sure the problem isn't here but I've been wrong before. private uint Pick() { Ray cursorRay = CalculateCursorRay(); Vector3? point = Control.Mesh.RayCast(cursorRay); if (point != null) { Tile hitTile = Control.TileMesh.GetTileAtPoint(point); return hitTile == null ? uint.MaxValue : (uint)(hitTile.X + hitTile.Y * Control.Generator.TilesWide); } return uint.MaxValue; } private Ray CalculateCursorRay() { Vector3 nearPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 0f)); Vector3 farPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 1f)); Vector3 direction = farPoint - nearPoint; direction.Normalize(); return new Ray(nearPoint, direction); } public Vector3 Camera.Unproject(Vector3 source) { Vector4 result; result.X = (source.X - _control.ClientRectangle.X) * 2 / _control.ClientRectangle.Width - 1; result.Y = (source.Y - _control.ClientRectangle.Y) * 2 / _control.ClientRectangle.Height - 1; result.Z = source.Z - 1; if (_farPlane - 1 == 0) result.Z = 0; else result.Z = result.Z / (_farPlane - 1); result.W = 1f; result = Vector4.Transform(result, Matrix4.Invert(ProjectionMatrix)); result = Vector4.Transform(result, Matrix4.Invert(ViewMatrix)); result = Vector4.Transform(result, Matrix4.Invert(_world)); result = Vector4.Divide(result, result.W); return new Vector3(result.X, result.Y, result.Z); } And my triangle intersection code. Ripped mainly from the XNA picking sample. public float? Intersects(Ray ray) { float? closestHit = Bounds.Intersects(ray); if (closestHit != null && Vertices.Length == 3) { Vector3 e1, e2; Vector3.Subtract(ref Vertices[1].Position, ref Vertices[0].Position, out e1); Vector3.Subtract(ref Vertices[2].Position, ref Vertices[0].Position, out e2); Vector3 directionCrossEdge2; Vector3.Cross(ref ray.Direction, ref e2, out directionCrossEdge2); float determinant; Vector3.Dot(ref e1, ref directionCrossEdge2, out determinant); if (determinant > -float.Epsilon && determinant < float.Epsilon) return null; float inverseDeterminant = 1.0f/determinant; Vector3 distanceVector; Vector3.Subtract(ref ray.Position, ref Vertices[0].Position, out distanceVector); float triangleU; Vector3.Dot(ref distanceVector, ref directionCrossEdge2, out triangleU); triangleU *= inverseDeterminant; if (triangleU < 0 || triangleU > 1) return null; Vector3 distanceCrossEdge1; Vector3.Cross(ref distanceVector, ref e1, out distanceCrossEdge1); float triangleV; Vector3.Dot(ref ray.Direction, ref distanceCrossEdge1, out triangleV); triangleV *= inverseDeterminant; if (triangleV < 0 || triangleU + triangleV > 1) return null; float rayDistance; Vector3.Dot(ref e2, ref distanceCrossEdge1, out rayDistance); rayDistance *= inverseDeterminant; if (rayDistance < 0) return null; return rayDistance; } return closestHit; } I'll admit I don't fully understand all of the math behind the intersection and that is something I'm working on, but my understanding was that if rayDistance was less than 0 the face was facing away from the camera, and shouldn't be counted as a hit. So my question is, is there an issue with my intersection or ray creation code, or is there another check I need to perform to tell if the face is facing away from the camera, and if so any hints on what that check might contain would be appreciated.

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  • openGL Camera setup for Zoom in/out centered at point under cursor

    - by user3228921
    I am trying to implement a zoom in/out navigation mode in a openGL 3dViewer. I was able to implement zoom functionality centered at screen center just by moving eye towards the center in perspective mode. Now i am trying to do the zoom centered at arbitrary position under the cursor. I am unable to figure out how should i move my camera forward and backward such that point under cursor remains at the same screen coordinates after zoom in/out. Any help would be appreciated. Below are the images which show the desired effect. Just to mention, I am working in a perspective mode with eye target and up vectors to control camera. Same effect i found in google sketchup and 'zoom to mouse position' setting in blender.

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  • A Star Path finding endless loop

    - by PoeHaH
    I have implemented A* algorithm. Sometimes it works, sometimes it doesn't, and it goes through an endless loop. After days of debugging and googling, I hope you can come to the rescue. This is my code: The algorythm: public ArrayList<Coordinate> findClosestPathTo(Coordinate start, Coordinate goal) { ArrayList<Coordinate> closed = new ArrayList<Coordinate>(); ArrayList<Coordinate> open = new ArrayList<Coordinate>(); ArrayList<Coordinate> travelpath = new ArrayList<Coordinate>(); open.add(start); while(open.size()>0) { Coordinate current = searchCoordinateWithLowestF(open); if(current.equals(goal)) { return travelpath; } travelpath.add(current); open.remove(current); closed.add(current); ArrayList<Coordinate> neighbors = current.calculateCoordAdjacencies(true, rowbound, colbound); for(Coordinate n:neighbors) { if(closed.contains(n) || map.isWalkeable(n)) { continue; } int gScore = current.getGvalue() + 1; boolean gScoreIsBest = false; if(!open.contains(n)) { gScoreIsBest = true; n.setHvalue(manhattanHeuristic(n,goal)); open.add(n); } else { if(gScore<n.getGvalue()) { gScoreIsBest = true; } } if(gScoreIsBest) { n.setGvalue(gScore); n.setFvalue(n.getGvalue()+n.getHvalue()); } } } return null; } What I have found out is that it always fails whenever there's an obstacle in the path. If I'm running it on 'open terrain', it seems to work. It seems to be affected by this part: || map.isWalkeable(n) Though, the isWalkeable function seems to work fine. If additional code is needed, I will provide it. Your help is greatly appreciated, Thanks :)

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