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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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  • Learning OpenGL ES 1.x

    - by Kristopher Johnson
    What is the quickest way to come up to speed on OpenGL ES 1.x? Let's assume I know nothing about OpenGL (which is not entirely true, but it's been a while since I last used OpenGL). I am most interested in learning this for iPhone-related development, but I'm interested in learning how it works on other platforms as well. I've found the book OpenGL ES 2.0 Programming Guide, but I am concerned that it might not be the best approach because it focuses on 2.0 rather than 1.x. My understanding is that 2.0 is not backwards-compatible with 1.x, so I may miss out on some important concepts. Note: For answers about learning general OpenGL, see http://stackoverflow.com/questions/62540/learning-opengl Some resources I've found: http://khronos.org/opengles/1_X/ http://www.imgtec.com/powervr/insider/sdk/KhronosOpenGLES1xMBX.asp OpenGL Distilled by Paul Martz (a good refresher on OpenGL basics)

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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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  • What is the most mature library to render equirectangular images in Flash?

    - by Dave Viner
    I have a series of equirectangular images. I'd like to display them in a custom Flash player so that the user could see the spherical nature of the images, and "look up", "look down", "look left/right" (or pan, zoom, etc). (Note that I have a long series of images, so the library must allow for dynamic loading of the images themselves, rather than having the images "baked" into the SWF player.) What is the best library to manage the display of the equirectangular images in Flash? By "best", I mean the most mature, most reliable, most robust, and fastest performing. For reference, an example of an equirectangular image can be found at http://archive.bigben.id.au/tutorials/360/background/projections.html.

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  • Interpolating height for a point inside a grid based on a discrete height function.

    - by fastrack20
    Hi, I have been wracking my brain to come up with a solution to this problem. I have a lookup table that returns height values for various points (x,z) on the grid. For instance I can calculate the height at A, B, C and D in Figure 1. However, I am looking for a way to interpolate the height at P (which has a known (x,z)). The lookup table only has values at the grid intervals, and P lies between these intervals. I am trying to calculate values s and t such that: A'(s) = A + s(C-A) B'(t) = B + t(P-B) I would then use the these two equations to find the intersection point of B'(t) with A'(s) to find a point X on the line A-C. With this I can calculate the height at this point X and with that the height at point P. My issue lies in calculating the values for s and t. Any help would be greatly appreciated.

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  • OpenGL - lighting of vertices outside clip range

    - by hmp
    I have a problem with lighting in my OpenGL application. When one of the vertices of a drawn polygon goes outside the front clip plane (or has z<0, I'm not sure which), the polygon stops being lighted properly. This however happens on only one machine I tested, with Intel GMA950 card. On nVidia and ATI cards everything looks fine. I guess I am breaking some OpenGL rule here? How should I deal with it? I'd try dividing the scene into smaller polygons, but I'm not sure if it guarantees the case is eliminated (all polygons stepping outside the clipping range are offscreen).

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  • Optimum ordering for packed vertex arrays on iPhone

    - by Pestilence
    Is there an optimum packing format for vertex arrays on the iPhone hardware? My textured (triangle) arrays are ordered: Vertex (x, y, z) Vertex Normal (x, y, z) Texture Coordinates (u, v) This is the way I've always done it. Should the UVs come before the normals? I'm not sure if it matters. I'd assume that the texturing & lighting units would have a preference, but I can't find anything about it. I certainly can't detect a difference.

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  • How to interpolate rotations?

    - by uhuu
    I have two vectors describing rotations; a start rotation A and a target rotation B. How would I best go about interpolating A by a factor F to approach B? Using a simple lerp on the vectors fails to work when more than one dimension needs to be interpolated (i.e. produces undesirable rotations). Maybe building quaternions from the rotation vectors and using slerp is the way to go. But how, then, could I extract a vector describing the new rotation from the resulting quaternion? Thanks in advance.

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  • How should I think about perspectives and rotation in OpenGL ES?

    - by Omega
    As I start to write rendering code, how do I want to consider my drawing operations? Will they always be relative to a fixed coordinate system on the screen, or does this change based on the camera perspective? The best example I can try to come up with is say I'm at (0,0,0) and I draw a line to (3,3,3). If I change the perspective +1 on the X axis and conduct the same operation, does it happen at (4,3,3), or am I just getting a new view of the line still being made at (3,3,3)? When doing rotation, am I moving the point from which a frustum emanates, or am I moving the rendering underneath?

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  • How can you deflect a direction/magnitude vector based on a direction/magnitude vector and a collided triangle?

    - by JeanOTF
    So, I have a Triangle-AABB collision algorithm and I have it returning the triangle that the AABB collided with. I was hoping with the 3 vectors of the triangle and the direction/magnitude of the movement would let me determine a deflected vector so that when you run against the wall at an angle you move slower, depending on the angle of collision, but along side the wall. This would remove the sticky collision problem with only moving when there is not a collision. Any suggestions or references would be greatly appreciated! Thanks.

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  • Getting object coordinates from camera

    - by user566757
    I've implemented a camera in Java using a position vector and three direction vectors so I can use gluLookAt(); moving around in `ghost mode' works fine enough, but I want to add collision detection. I can't seem to figure out how to transform my position vector to coordinates in which OpenGL draws my objects. A rough sketch of my drawing loop is this: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); camera.setView(); drawer.drawTheScene(); I'm at a loss of how to proceed; looking at the ModelView matrix between calls and my position vector, I haven't found any kind of correlation.

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  • How can I make 3ds files' size smaller??

    - by Shaza
    Hey all, Is there any way I can use to make the size of a 3ds file smaller?? I tried to change their length and width using 3dmax but the file size still the same?? I'm using the 3ds files in creating an OpenGl scene so I need to shrink their size as small as I can, any suggestions??

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  • Cloning ID3DXMesh with declration that has 12 floats breaks?

    - by meds
    I have the following vertex declration: struct MESHVERTInstanced { float x, y, z; // Position float nx, ny, nz; // Normal float tu, tv; // Texcoord float idx; // index of the vertex! float tanx, tany, tanz; // The tangent const static D3DVERTEXELEMENT9 Decl[6]; static IDirect3DVertexDeclaration9* meshvertinstdecl; }; And I declare it as such: const D3DVERTEXELEMENT9 MESHVERTInstanced::Decl[] = { { 0, 0, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_POSITION, 0 }, { 0, 12, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_NORMAL, 0 }, { 0, 24, D3DDECLTYPE_FLOAT2, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 0 }, { 0, 32, D3DDECLTYPE_FLOAT1, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TEXCOORD, 1 }, { 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 }, D3DDECL_END() }; What I try to do next is copy an ID3DXMesh into another one with the new vertex declaration as such: model->CloneMesh( model->GetOptions(), MESHVERTInstanced::Decl, gd3dDevice, &pTempMesh ); When I try to get the FVF size of pTempMesh (D3DXGetFVFVertexSize(pTempMesh-GetFVF())) I get '0' though the size should be 48. The whole thing is fine if I don't have the last declaration, '{ 0, 36, D3DDECLTYPE_FLOAT3, D3DDECLMETHOD_DEFAULT, D3DDECLUSAGE_TANGENT, 0 },' in it and the CloneMesh function does not return a FAIL. I've also tried using different declarations such as D3DDECLUSAGE_TEXCOORD and that has worked fine, returning a size of 48. Is there something specific about D3DDECLUSAGE_TANGENT I don't know? I'm at a complete loss as to why this isn't working...

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  • Move an object in the direction of a bezier curve?

    - by Sent1nel
    I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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