[HOpenGL] draw Elements segmentation fault.

[Ben Christy]

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 <bkomuves at gmail.com> 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 <ben.christy at gmail.com>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 <ben.christy at gmail.com>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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