Re: draw Elements segmentation fault.

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 <[email protected]> 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 <[email protected]>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?
>>
>>
>>

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