On Nov 9, 3:20 pm, Alex Holkner <[EMAIL PROTECTED]> wrote:
> LaundroMat wrote:
> > Hi,
>
> > When running the following code from within Gutsy, the results are
> > unpredictable: one time I see a gradient-filled triangle, other times
> > what seems to me is just random gfx memory is being displayed.
>
> > glColorPointer (3, GL_FLOAT, 6 * sizeof(GLfloat), (GLfloat *
> > len(intertwined))(*intertwined))
> > glVertexPointer (3, GL_FLOAT, 6 * sizeof(GLfloat), (GLfloat *
> > len(intertwined[3:]))(*intertwined[3:]))
>
> > glBegin(GL_TRIANGLES)
> > glArrayElement (2)
> > glArrayElement (3)
> > glArrayElement (5)
> > glEnd()
>
> The arrays of vertex and color data are being garbage collected as soon
> as the glColorPointer and glVertexPointer functions return. Differences
> in the implementation of malloc on Windows and Linux are causing the
> data to be overwritten before glArrayElement is being called.
>
> The solution is to hold the arrays in free variables so that they are
> not released until the function is left. e.g.:
>
> color_data = (GLfloat * len(intertwined))(*intertwined)
> glColorPointer(3, GL_FLOAT, 6 * sizeof(GLfloat), color_data)
>
> [Side note: the data will not actually be intertwined in your example,
> as the slice [3:] creates a copy of the list. You can achieve the
> effect I believe you are after with some ctypes trickery to mangle a
> pointer into the color array (but it's almost certainly easier to use
> glInterleavedArrays with GL_C3F_V3F). Apologies if you knew this
> already and were just trying something different :-) ]
>
> Alex.
I'll check this out later, but many thanks already for the speedy and
informative reply! (And thanks for the side note: I was indeed
planning on using interleaved arrays, but I was indeed trying to
explore all the different ways of doing things).
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