Re: [HOpenGL] draw Elements segmentation fault.

Issue resolved. The problem was that I thought glVertexAttribPointer 1 3 GLRaw.gl_FLOAT 0 0 (plusPtr nullPtr (0)) was one based when in fact it is 0 based so changing the call to glVertexAttribPointer 0 3 GLRaw.gl_FLOAT 0 0 (plusPtr nullPtr (0)) resolves the issue. Thank you for pointing out where the problem was. On Fri, Nov 19, 2010 at 7:26 AM, Balazs Komuves wrote:

Hi,

Still guessing (I can't try your code at the moment), but it seems that you want to use vertex arrays, however you set up the vertex *attribute* array pointer, which are two different things. Vertex attributes are arbitrary parameters associated with vertices, to be used by vertex shaders.

Balazs

On Fri, Nov 19, 2010 at 3:38 AM, Ben Christy wrote:

...

Ok I stripped this down to the barest form and I still get segmentation faults here is the code. I am at a loss as this seems to be identical to C code posted in examples all over the web. Any thoughts?

main = do (progname, _) ← getArgsAndInitialize createWindow "Ben Christy Assignment 2" windowSize $= Size 800 600 matrixMode $= Projection loadIdentity depthFunc $= Just Less viewport $= (Position 0 0, Size 800 600) perspective 60 1.333 1 120 changesRef ← newIORef Map.empty --sceneRef ← newIORef buildSSG sceneRef ← newIORef (SimpleRootNode "HomeWork3" [ TransformNode "camera" (Rotate 0 90 0) (Translate 0 0 (-1)) [ TransformNode "ground" (Rotate 0 0 0) (Translate (-4) (-1.5) (-4)) [ ModelNode "groundModel" (Just (buildModel ModernGL (heightMapToVerts(genHeightMap 2 1 1.6 1.2 1.7) 0.1 0 3) (0,0,0) (buildShader defaultVertexShader defaultFragmentShader))) ] ] ]) --pollsRot ← newIORef 0 --evenState ← newIORef BackAgain --evenPos ← newIORef 0.25 --oddState ← newIORef There --oddPos ← newIORef 0.15 --balloonNumSteps ← newIORef 100 reshapeCallback $= Just reshape displayCallback $= (displayScene sceneRef changesRef ) --addTimerCallback 10 (animate sceneRef pollsRot changesRef evenState evenPos oddState oddPos) --keyboardMouseCallback $= Just (handleInput sceneRef changesRef) mainLoop

displayScene sceneRef changesRef= do --changes ← readIORef changesRef --oldSceneGraph ← readIORef sceneRef --sceneGraph ← return $ updateSceneGraph changes oldSceneGraph --render identityMatrix sceneGraph --writeIORef changesRef Map.empty --writeIORef sceneRef sceneGraph clear [ColorBuffer, DepthBuffer] lighting $= Enabled light (Light 0) $= Enabled matrixMode $= Modelview 0 loadIdentity [vbo] ← genObjectNames 1 :: IO [BufferObject] bindBuffer ArrayBuffer $= Just vbo tempArray ← newListArray (0, 8) [0,0,0,0,0.5,0,0.5,0.5,0.5] :: IO(StorableArray Int GLfloat) withStorableArray tempArray (λptr -> bufferData ArrayBuffer $= ((fromIntegral (9*4), ptr, StaticDraw))) print " Setting attrib pointer" vertexAttribArray (AttribLocation 1) $= Enabled GLRaw.glVertexAttribPointer 1 3 GLRaw.gl_FLOAT 0 0 (plusPtr nullPtr (0)) clientState VertexArray $= Enabled print "before draw" drawArrays Triangles 0 3 print "after draw" --resetAttribPtr program bindBuffer ArrayBuffer $= Nothing clientState VertexArray $= Disabled return ()

reshape (Size w h) = do print "resize" matrixMode $= Projection loadIdentity depthFunc $= Just Less viewport $= (Position 0 0, Size w h) perspective 60 1.333 0.01 120 matrixMode $= Modelview 0 loadIdentity postRedisplay Nothing

On Thu, Nov 18, 2010 at 10:37 AM, Ben Christy wrote:

...

I have tried drawElements Triangles (fromIntegral 1) UnsignedInt nullPtr--(fromIntegral count)

Test.withArray [ (i) | i<-[0..count-1] ] $ \p -> drawElements Points10 UnsignedInt p

drawArrays Points 1 10

All three of which cause a segmentation thought. I am kind of at a loss, is it possible that the buffers are empty? If so what is the best way to check?