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Re: [Public WebGL] Ambiguity and Non-deterministicness in the WebGL Spec
On 13/12/2010 07:20, Gregg Tavares (wrk) wrote:
The spec has changed to effectively require a clear
each time the WebGL draw buffer is composited
Please remind me why this clearing is necessary. If it is for
"security" then surely this extra clearing is only necessary if the
drawingBuffer is given to a different webgl context that original
drew the contents.
As I pointed out in a previous e-mail not all applications use
glClear() because their other rendering will fill the entire buffer.
In those cases following the above is overhead that cannot be
optimized away. When I was at SGI, we used to go to enormous lengths
to make sure the clear operation was fast because it has an enormous
effect on the overall frame-rate. It feels really painful to be
introducing extra clears.
readPixels is defined to read pixels from the current write buffer
(i.e. the drawing buffer). Other than for that, it's a fair
I also don't quite understand this part
preserveDrawingBuffer attribute of
the WebGLContextAttributes object
to true, the contents of the drawing buffer can be
preserved until the author either clears or overwrites
them. If this
flag is false attempting to perform operations using
this context as a source image after the rendering
function has returned can lead to undefined behavior.
or using this context as the source image of another
That seems counter intuitive. The browser has the pixels. It
has to be able to display them. Why do these functions have to
have undefined behavior?
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