Hi, I'm just guessing here, but I believe the problem is with the line drawElements Triangles (fromIntegral count) UnsignedInt nullPtr
Look up 'drawElements' in the OpenGL specification (page 29 in http://www.opengl.org/documentation/specs/version2.0/glspec20.pdf): The command
void DrawElements( enum mode, sizei count, enum type, void *indices );
constructs a sequence of geometric primitives using the count elements whose indices are stored in indices. type must be one of UNSIGNED BYTE, UNSIGNED SHORT, or UNSIGNED INT, indicating that the values in indices are indices of GL type ubyte, ushort, or uint respectively. Mode specifies what kind of primitives are constructed; it accepts the same token values as the mode parameter of the Begin command. The effect of DrawElements (mode, count, type, indices); is the same as the effect of the command sequence
if (mode, count, or type is invalid )
generate appropriate error else { Begin(mode); for (int i = 0; i < count ; i++) ArrayElement(indices[i]); End(); }
So, I think you actually want to use 'drawArrays' instead. But without seeing the full source, I'm again just guessing. I believe 'drawElements' should be used like this (I'm writing this from the top of head, so take it with a grain of salt): withArray [ (3*i :: GLuint) | i<-[0..count-1] ] $ \p -> drawElements
Triangles count UnsignedInt p
Balazs
On Thu, Nov 18, 2010 at 2:53 AM, Ben Christy
I am having a issue getting a seg fault with drawElements. Honestly I can not tell where the problem is. It seems as far as all I have read that it should work and being its written in haskell I am asking here first before asking in an opengl chat room. I init my VBOs with
initModelIBO :: Int → IO BufferObject initModelIBO listLen = do print "list length" print listLen print "gen ibo bytes" print sizeOfList [ibo] ← genObjectNames 1 :: IO [BufferObject] bindBuffer ElementArrayBuffer $= Just ibo tempArray2 ← newListArray (0, listLen - 1) indexList :: IO(StorableArray Int GLuint) withStorableArray tempArray2 (λptr -> bufferData ElementArrayBuffer $= ((fromIntegral sizeOfList), ptr, StaticDraw)) bindBuffer ElementArrayBuffer $= Nothing return ibo where elementSize = 4 sizeOfList = listLen * elementSize indexList = [i | i ← [0..(fromIntegral listLen)]] :: [GLuint]
initModelVBO :: [Vert] → IO BufferObject initModelVBO vertexList = do print "list length" print listLen print "gen vbo bytes" print sizeOfList [vbo] ← genObjectNames 1 :: IO [BufferObject] bindBuffer ArrayBuffer $= Just vbo tempArray ← newListArray (0, listLen - 1) vertList :: IO(StorableArray Int GLfloat) withStorableArray tempArray (λptr -> bufferData ArrayBuffer $= ((fromIntegral sizeOfList), ptr, StaticDraw)) bindBuffer ArrayBuffer $= Nothing return vbo where elementsPerVert = 10 vertList = vertsToList vertexList listLen = length vertList elementSize = 4 sizeOfList = listLen * elementSize
My Vert type is data Vert = Vert { vertX ::GLfloat, vertY ::GLfloat, vertZ ::GLfloat, --normalX ::GLfloat, --normalY ::GLfloat, --normalZ ::GLfloat, colorR ::GLfloat, colorG ::GLfloat, colorB ::GLfloat, specR ::GLfloat, specG ::GLfloat, specB ::GLfloat, shiny ::GLfloat} deriving (Show)
I set vertex attributes with setAttribPtr (Just program) = do print " Setting attrib pointer"
--vertexAttribPointer (AttribLocation 1) $= (KeepIntegral, (VertexArrayDescriptor 3 Float ((4) *10) (plusPtr nullPtr (0*4)))) GLRaw.glVertexAttribPointer 1 3 GLRaw.gl_FLOAT 0 stride (plusPtr nullPtr (0)) vertexAttribArray (AttribLocation 1) $= Enabled --vertexAttribPointer (AttribLocation 2) $= (KeepIntegral, (VertexArrayDescriptor 3 Float ((4) *10) (plusPtr nullPtr (3*4)))) GLRaw.glVertexAttribPointer 2 3 GLRaw.gl_FLOAT 0 stride (plusPtr nullPtr (12)) vertexAttribArray (AttribLocation 2) $= Enabled --vertexAttribPointer (AttribLocation 3) $= (KeepIntegral, (VertexArrayDescriptor 3 Float ((4) *10) (plusPtr nullPtr (6*4)))) GLRaw.glVertexAttribPointer 3 3 GLRaw.gl_FLOAT 0 stride (plusPtr nullPtr (24)) vertexAttribArray (AttribLocation 3) $= Enabled
--vertexAttribPointer (AttribLocation 4) $= (KeepIntegral, (VertexArrayDescriptor 1 Float ((4) *10) (plusPtr nullPtr (9*4)))) GLRaw.glVertexAttribPointer 4 1 GLRaw.gl_FLOAT 0 stride (plusPtr nullPtr (36)) vertexAttribArray (AttribLocation 4) $= Enabled return () where stride = 40
I build a shader program with buildShader vertexShader fragmentShader = do [vertObj] ← genObjectNames 1 ::IO [VertexShader] shaderSource vertObj $= [vertexShader] compileShader vertObj vsLog ← get (shaderInfoLog vertObj) print "vertex shader status" print vsLog [fragObj] ← genObjectNames 1 ::IO [FragmentShader] shaderSource fragObj $= [fragmentShader] compileShader fragObj fsLog ← get (shaderInfoLog fragObj) print "fragment shader status" print fsLog [programObj] ← genObjectNames 1 ::IO [Program] attachedShaders programObj $= ([vertObj], [fragObj]) attribLocation programObj "position" $= AttribLocation 1 attribLocation programObj "color" $= AttribLocation 2 attribLocation programObj "spec" $= AttribLocation 3 attribLocation programObj "shiny" $= AttribLocation 4 linkProgram programObj progLog ← get(programInfoLog programObj) print "Shader Program status" print progLog return (Just programObj)
Finally my render function
instance RenderSimpleSceneGraph Model where render matrix (ModernModel vbo ibo shader count) = do clientState VertexArray $= Enabled version ← get (majorMinor glVersion) tempVBO ← vbo tempIBO ← ibo print "Render Modern Model" program ← shader currentProgram $= program bindBuffer ArrayBuffer $= Just tempVBO setAttribPtr program bindBuffer ElementArrayBuffer $= Just tempIBO print "here" drawElements Triangles (fromIntegral count) UnsignedInt nullPtr print "here1" resetAttribPtr program bindBuffer ArrayBuffer $= Nothing clientState VertexArray $= Disabled
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