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  • Finding intersection of two spheres

    - by Onkar Deshpande
    Hi, Consider the following problem - I am given 2 links of length L0 and L1. P0 is the point that the first link starts at and P1 is the point that I want the end of second link to be at in 3-D space. I am supposed to write a function that should take in these 3-D points (P0 and P1) as inputs and should find all configurations of the links that put the second link's end point at P1. My understanding of how to go about it is - Each link L0 and L1 will create a sphere S0 and S1 around itself. I should find out the intersection of those two spheres (which will be a circle) and print all points that are on the circumference of that circle. I saw gmatt's first reply on the http://stackoverflow.com/questions/1406375/finding-intersection-points-between-3-spheres but could not understand it properly since the images did not show up. I also saw a formula for finding out the intersection at mathworld[dot]wolfram[dot]com/Sphere-SphereIntersection[dot]html . I could find the radius of intersection by the method given on mathworld. Also I can find the center of that circle and then use the parametric equation of circle to find the points. The only doubt that I have is will this method work for the points P0 and P1 mentioned above ? Please comment and let me know your thoughts.

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  • How to use Mesa3D on Mac OS X and Windows

    - by gutsblow
    Hello all, I need to use Mesa3D for a cross platform application(windows and Mac only) which uses only offline software rendering. The reason I wanted to use Mesa3D is because it has the same Drawing calls as OpenGL and they are really easy. Now I know that Apple itself has a software implementation (which I heard is flaky), but I prefer using Mesa so that it's a lot easier for me to maintain the code on both platforms. On windows I managed to compile three DLL's from the Mesa3d source, but don't know what to do with them. On Mac OS X I am completely clueless. I would highly appreciate your help. Thank you once again very much!

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  • Intersection of line with cube and knowing the point of intersection.

    - by Raj
    Hello everyone, description 1.lines are originating from origin(0,0,0). 2.lines are at some random angle to the Normal of Top face of teh cube. 3.if the lines are intersecting cube , calculate the intersection point. 4.mainly i wan to know how much distance ,line traveled inside the cube. I dont know exactly which approach should i take , i will be pleased and thankful if someone could guied me to the right direction, to use OpenGL, DirectX or some other library, for C# . some example or sample will be appriciated.

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  • How to fix rotations in a Rubik's Cube?

    - by Eindbaas
    I'm trying to create a Rubik's Cube in Flash & Papervision and i'm really stuck here. I'm up to the point where i can rotate any plane of cubes once, but after that...it's messed up because all local coordinate systems are messy. I dont really know where to go from here, can anybody give any advice on what do do? I'm not looking for 'read about transformation matrices', i know i should (and i am doing that), but i'm not really sure what to look for. My idea is that, after each rotation, i should fix each coordinate system of each cube again, but i have no idea how. Any hints on what i want to achieve (in words), and why, are much appreciated. http://dl.dropbox.com/u/250155/rubik/main.html (you can press the K key once ;) )

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  • Creating a tiled world with OpenGL

    - by Tamir
    Hello, I'm planning to create a tiled world with OpenGL, with slightly rotated tiles and houses and building in the world will be made of models. Can anybody suggest me what projection(Orthogonal, Perspective) should I use, and how to setup the View matrix(using OpenGL)? If you can't figure what style of world I'm planning to create, look at this game: http://www.youtube.com/watch?v=i6eYtLjFu-Y&feature=PlayList&p=00E63EDCF757EADF&index=2

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  • How does the "Unlimited Detail" graphics technology work?

    - by daddz
    So I stumbled upon this "new" graphics engine/technology called Unlimited Detail. This seems to be pretty interesting granted it's real and not a fake. They have some videos explaining the technology but they only scratch the surface. What do you think about it? Is it programmatically possible? Or is it just a scam for investors?

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  • Problem implementing Blinn–Phong shading model

    - by Joe Hopfgartner
    I did this very simple, perfectly working, implementation of Phong Relflection Model (There is no ambience implemented yet, but that doesn't bother me for now). The functions should be self explaining. /** * Implements the classic Phong illumination Model using a reflected light * vector. */ public class PhongIllumination implements IlluminationModel { @RGBParam(r = 0, g = 0, b = 0) public Vec3 ambient; @RGBParam(r = 1, g = 1, b = 1) public Vec3 diffuse; @RGBParam(r = 1, g = 1, b = 1) public Vec3 specular; @FloatParam(value = 20, min = 1, max = 200.0f) public float shininess; /* * Calculate the intensity of light reflected to the viewer . * * @param P = The surface position expressed in world coordinates. * * @param V = Normalized viewing vector from surface to eye in world * coordinates. * * @param N = Normalized normal vector at surface point in world * coordinates. * * @param surfaceColor = surfaceColor Color of the surface at the current * position. * * @param lights = The active light sources in the scene. * * @return Reflected light intensity I. */ public Vec3 shade(Vec3 P, Vec3 V, Vec3 N, Vec3 surfaceColor, Light lights[]) { Vec3 surfaceColordiffused = Vec3.mul(surfaceColor, diffuse); Vec3 totalintensity = new Vec3(0, 0, 0); for (int i = 0; i < lights.length; i++) { Vec3 L = lights[i].calcDirection(P); N = N.normalize(); V = V.normalize(); Vec3 R = Vec3.reflect(L, N); // reflection vector float diffuseLight = Vec3.dot(N, L); float specularLight = Vec3.dot(V, R); if (diffuseLight > 0) { totalintensity = Vec3.add(Vec3.mul(Vec3.mul( surfaceColordiffused, lights[i].calcIntensity(P)), diffuseLight), totalintensity); if (specularLight > 0) { Vec3 Il = lights[i].calcIntensity(P); Vec3 Ilincident = Vec3.mul(Il, Math.max(0.0f, Vec3 .dot(N, L))); Vec3 intensity = Vec3.mul(Vec3.mul(specular, Ilincident), (float) Math.pow(specularLight, shininess)); totalintensity = Vec3.add(totalintensity, intensity); } } } return totalintensity; } } Now i need to adapt it to become a Blinn-Phong illumination model I used the formulas from hearn and baker, followed pseudocodes and tried to implement it multiple times according to wikipedia articles in several languages but it never worked. I just get no specular reflections or they are so weak and/or are at the wrong place and/or have the wrong color. From the numerous wrong implementations I post some little code that already seems to be wrong. So I calculate my Half Way vector and my new specular light like so: Vec3 H = Vec3.mul(Vec3.add(L.normalize(), V), Vec3.add(L.normalize(), V).length()); float specularLight = Vec3.dot(H, N); With theese little changes it should already work (maby not with correct intensity but basically it should be correct). But the result is wrong. Here are two images. Left how it should render correctly and right how it renders. If i lower the shininess factor you can see a little specular light at the top right: Altough I understand the concept of Phong illumination and also the simplified more performant adaptaion of blinn phong I am trying around for days and just cant get it to work. Any help is appriciated. Edit: I was made aware of an error by this answer, that i am mutiplying by |L+V| instead of dividing by it when calculating H. I changed to deviding doing so: Vec3 H = Vec3.mul(Vec3.add(L.normalize(), V), 1/Vec3.add(L.normalize(), V).length()); Unfortunately this doesnt change much. The results look like this: and if I rise the specular constant and lower the shininess You can see the effects more clearly in a smilar wrong way: However this division just the normalisation. I think I am missing one step. Because the formulas like this just dont make sense to me. If you look at this picture: http://en.wikipedia.org/wiki/File:Blinn-Phong_vectors.svg The projection of H to N is far less than V to R. And if you imagine changing the vector V in the picture the angle is the same when the viewing vector is "on the left side". and becomes more and more different when going to the right. I pesonally would multiply the whole projection by two to become something similiar (and the hole point is to avoid the calculation of R). Altough I didnt read anythinga bout that anywehre i am gonna try this out... Result: The intension of the specular light is far too much (white areas) and the position is still wrong. I think I am messing something else up because teh reflection are just at the wrong place. But what? Edit: Now I read on wikipedia in the notes that the angle of N/H is in fact approximalty half or V/R. To compensate that i should multiply my shineness exponent by 4 rather than my projection. If i do that I end up with this: Far to intense but still one thing. The projection is at the wrong place. Where could i mess up my vectors?

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  • OpenGL ES canvas size

    - by Chaoz
    Ahoy, I'm working on an OpenGL ES based game for Android using the NDK. My application is targeted towards SDK 1.6 and above. I seem to be having a problem creating a canvas of the phones native size. My rendering is done through a native gameloop that uses OpenGL 1.0. I'm using the emulator and that gives me a 480x320 canvas -- this is totally fine. Then, when I run the same application on my HTC Desire which has a native resolution of 800x480 I'm getting a canvas of 533x320. Anyone have any information on how to deal with/solve this? Any other information about this is also appreciated. Thanks in advance!

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  • Shape object in Processing, translate individual shapes.

    - by Zain
    I am relatively new to Processing but have been working in Java for about 2 years now. I am facing difficulty though with the translate() function for objects as well as objects in general in processing. I went through the examples and tried to replicate the manners by which they instantiated the objects but cannot seem to even get the shapes to appear on the screen no less move them. I instantiate the objects into an array using a nested for loop and expect a grid of the objects to be rendered. However, nothing at all is rendered. My nested for loop structure to instantiate the tiles: for(int i=0; i<102; i++){ for(int j=0; j<102; j++){ tiles[i][j]=new tile(i,0,j); tiles[i][j].display(); } } And the constructors for the tile class: tile(int x, int y, int z){ this.x=x; this.y=y; this.z=z; beginShape(); vertex(x,y,z); vertex(x+1,y,z); vertex(x+1,y,z-1); vertex(x,y,z-1); endShape(); } Nothing is rendered at all when this runs. Furthermore, if this is of any concern, my translations(movements) are done in a method I wrote for the tile class called move which simply calls translate. Is this the correct way? How should one approach this? I can't seem to understand at all how to render/create/translate individual objects/shapes. Thanks for any help any of you are able to provide!

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  • Java3d resetting to a new scene

    - by Dan Howard
    Hi all, I'm working on a game in Java3D. I read all my level info from a file and it works fine. But now I want to re-initialize the scene from reading data from a different file. How do I reset the scene? Should I just destroy the whole canvas3D and universe objects?

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  • Need guidelines for optimizing WebGL performance by minimizing shader changes

    - by brainjam
    I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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  • Most efficient algorithm for mesh-level, optimal occlusion culling?

    - by Fredriku73
    I am new to culling. On a first glance, it seems that most occlusion culling algorithms are object-level, not examining single meshes, which would be practical for game rendering. What I am looking for is an algorithm that culls all meshes within a single object that are occluded for a given viewpoint, with high accuracy. It needs to be at least O(n log n), a naive mesh-by-mesh comparison (O(n^2)) is too slow. I notice that the Blender GUI identifies the occluded meshes for you in real-time, even if you work with large objects of 10,000+ meshes. What algorithm is used there, pray tell?

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  • Bilinear interpolation - DirectX vs. GDI+

    - by holtavolt
    I have a C# app for which I've written GDI+ code that uses Bitmap/TextureBrush rendering to present 2D images, which can have various image processing functions applied. This code is a new path in an application that mimics existing DX9 code, and they share a common library to perform all vector and matrix (e.g. ViewToWorld/WorldToView) operations. My test bed consists of DX9 output images that I compare against the output of the new GDI+ code. A simple test case that renders to a viewport that matches the Bitmap dimensions (i.e. no zoom or pan) does match pixel-perfect (no binary diff) - but as soon as the image is zoomed up (magnified), I get very minor differences in 5-10% of the pixels. The magnitude of the difference is 1 (occasionally 2)/256. I suspect this is due to interpolation differences. Question: For a DX9 ortho projection (and identity world space), with a camera perpendicular and centered on a textured quad, is it reasonable to expect DirectX.Direct3D.TextureFilter.Linear to generate identical output to a GDI+ TextureBrush filled rectangle/polygon when using the System.Drawing.Drawing2D.InterpolationMode.Bilinear setting? For this (magnification) case, the DX9 code is using this (MinFilter,MipFilter set similarly): Device.SetSamplerState(0, SamplerStageStates.MagFilter, (int)TextureFilter.Linear); and the GDI+ path is using: g.InterpolationMode = InterpolationMode.Bilinear; I thought that "Bilinear Interpolation" was a fairly specific filter definition, but then I noticed that there is another option in GDI+ for "HighQualityBilinear" (which I've tried, with no difference - which makes sense given the description of "added prefiltering for shrinking") Followup Question: Is it reasonable to expect pixel-perfect output matching between DirectX and GDI+ (assuming all external coordinates passed in are equal)? If not, why not? Finally, there are a number of other APIs I could be using (Direct2D, WPF, GDI, etc.) - and this question generally applies to comparing the output of "equivalent" bilinear interpolated output images across any two of these. Thanks!

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  • Flipping issue when interpolating Rotations using Quaternions

    - by uhuu
    I use slerp to interpolate between two quaternions representing rotations. The resulting rotation is then extracted as Euler angles to be fed into a graphics lib. This kind of works, but I have the following problem; when rotating around two (one works just fine) axes in the direction of the green arrow as shown in the left frame here the rotation soon jumps around to rotate from the opposite site to the opposite visual direction, as indicated by the red arrow in the right frame. This may be logical from a mathematical perspective (although not to me), but it is undesired. How could I achieve an interpolation with no visual flipping and changing of directions when rotating around more than one axis, following the green arrow at all times until the interpolation is complete? Thanks in advance.

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  • Converting OpenGL co-ordinates to lower UIView (and UIImagePickerController)

    - by John Qualis
    Hi, I am new to OpenGL over iPhone. I am developing an iPhone app similar to a barcode reader but with an extra OpenGL layer. The bottommost layer is UIImagePickerController, then I use UIView on top and draw a rectangle at certain co-ordinates on the iphone screen. So far everything is OK. Then I am trying to draw an OpenGL 3-D model in that rectangle. I am able to load a 3-D model in the iPhone based on this code here - http://iphonedevelopment.blogspot.com/2008/12/start-of-wavefront-obj-file-loader.html I am not able to transform the co-ordinates of the rectangle into OpenGL co-ordinates. Appreciate any help. Do I need to use a matrix to translate the currentPosition of the 3-D model so it is drawn within myRect? The code is given below.. Appreciate any help/pointers in this regards. John -(void)setupView:(GLView*)view { const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0; GLfloat size; glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); CGRect rect = view.bounds; glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar); glViewport(0, 0, rect.size.width, rect.size.height); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glClearColor(0.0f, 0.0f, 0.0f, 0.0f); NSString *path = [[NSBundle mainBundle] pathForResource:@"plane" ofType:@"obj"]; OpenGLWaveFrontObject *theObject = [[OpenGLWaveFrontObject alloc] initWithPath:path]; Vertex3D position; position.z = -8.0; position.y = 3.0; position.x = 2.0; theObject.currentPosition = position; self.plane = theObject; [theObject release]; } (void)drawView:(GLView*)view; { static GLfloat rotation = 0.0; glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glColor4f(0.0, 0.5, 1.0, 1.0); // the coordinates of the rectangle are // myRect.x, myRect.y, myRect.width, myRect.height // Do I need to use a matrix to translate the currentPosition of the // 3-D model so it is drawn within myRect? //glOrthof(-160.0f, 160.0f, -240.0f, 240.0f, -1.0f, 1.0f); [plane drawSelf]; }

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  • How to setup/calculate texturebuffer in glTexCoordPointer when importing from OBJ-file

    - by JohnMurdoch
    Hi all, I'm parsing an OBJ-file in Android and my goal is to render & display the object. Everything works fine except the correct texture mapping (importing the resource/image into opengl etc works fine). I don't know how to populate the texture related data from the obj-file into an texturebuffer-object. In the OBJ-file I've vt-lines: vt 0.495011 0.389417 vt 0.500686 0.561346 and face-lines: f 127/73/62 98/72/62 125/75/62 My draw-routine looks like (only relevant parts): gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_NORMAL_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glNormalPointer(GL10.GL_FLOAT, 0, normalsBuffer); gl.glTexCoordPointer(2, GL10.GL_SHORT, 0, t.getvtBuffer()); gl.glDrawElements(GL10.GL_TRIANGLES, t.getFacesCount(), GL10.GL_UNSIGNED_SHORT, t.getFaceBuffer()); Output of the counts of the OBJ-file: Vertex-count: 1023 Vns-count: 1752 Vts-count: 524 ///////////////////////// Part 0 Material name:default Number of faces:2037 Number of vnPointers:2037 Number of vtPointers:2037 Any advise is welcome.

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  • How do I map a texture onto a Octahedron?

    - by Justin808
    I'm about to go mad. I cant for the life of me figure out texture coords. I have a Octahedron defined by the 8 triangles below. I want to map a texture of the earth on it. See the texture here: http://img37.imageshack.us/f/earthmap1k.jpg/ I would like the north pole at the top point and the south pole at the oposite point with the equator wrapped around the center points. Can someone show me the UVs for each point to map the texture please? 0, 0, 1 1, -1, 0 1, 1, 0 -1, 1, 0 0, 0, 1 1, 1, 0 0, 0, 1 -1, 1, 0 -1, -1, 0 1, -1, 0 0, 0, 1 -1, -1, 0 1, -1, 0 0, 0, -1 1, 1, 0 0, 0, -1 -1, 1, 0 1, 1, 0 0, 0, -1 -1, -1, 0 -1, 1, 0 0, 0, -1 1, -1, 0 -1, -1, 0

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  • How to implement an ItemsControl3D which can use templates of Visual3D?

    - by Christo
    I'm looking for something like a ContainerUIElement3D which supports the ItemsSource property and an ItemTemplate property which I can use within a Viewport3D. My aim is to be able to write something like: <ItemsControl3D ItemsSource="{Binding Path=MyItems}"> <ItemsControl3D.ItemTemplate> <DataTemplate3D> <!-- My template which defines the binding to each item. --> <DataTemplate3D> </ItemsControl3D.ItemTemplate> </ItemsControl3D> I'm looking for tips on how to implement this. The first tricky part is to create a DataTemplate3D which can construct the Visual3D needed to add to the ItemsControl3D. I've been using .NET reflector to browse through the implementation of ItemsControl and DataTemplate, but I soon realised that I don't have a deep enough understanding and enough time to come up with a solution on my own.

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  • How do you determine when an object is drawn on-screen in OpenGL?

    - by Harry
    I'm extremely new to OpenGL. I'm writing a program that displays flying text on screen. I need to know when certain text string appears (drawn) onto the screen and are visible to the user. The program needs to identify which text strings are displayed. At first, I started to think that I could use OpenGL's picking mechanism, but so far I've only seen examples where the selection area is focused on some sort of user interaction. I want to know what objects are displayed on the entire window area. This leads me to think I'm on the wrong track... Am I missing something? Any suggestions are welcome.

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  • From a Maya scene to a WebGL animation, where to start?

    - by Tower
    Hi, I've got some time, and I really would like to learn to get my Maya animated scenes into WebGL. I'm not sure where to start really. It would be amazing if I could make a Canvas element and place a Maya scene into it so that it's animating. Does anyone got a tutorial or some hints? PS. Answers about 3ds Max are also welcome!

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  • In MAYA 2009, is it possible to capture the cube rotate event?

    - by Rahul2047
    I need to call a function ( Maya-Python ) based on cube rotationX. For that I have to capture the event, programmatically. I tried using while loop but It stucks in the loop, Nothing can be done in that time. I tried theading (python), still same. Can it be done this or other way? If yes, How? Maya 2009 in Windows XP Some failed code references: import maya.cmds as cmds while (count < 90): lock = cmds.getAttr('pCube1.rotateX',lock=False) print lock count = count + 1 Here Python wise: #!/usr/bin/python import thread import time # Define a function for the thread def cubeRotateX( threadName, delay): count = 0 while count < 5: time.sleep(delay) count += 1 try: thread.start_new_thread( cubeRotateX, ("Thread-1", 2, ) ) except: print "Error: unable to start thread" while 1: pass

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  • Using CreateOrthographicOffCenter in XNA

    - by Jeffrey Kern
    I'm trying to figure out how to draw graphics in XNA, and someone else suggested this. But before I attempt to use this... If I create and use this camera, and set LEFT,TOP to 0 and WIDTH=256 and HEIGHT=240, anything I render to the screen will use these coordinates? So a box with a width and height of 1, if set to 0,0 will take up space from 0,0 to 1,1?

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