The trivially parallel renderer fails on a number of levels. The color of the circle intersections are incorrect because the color rendering is done in the incorrect order--in fact, it's entirely non-deterministic, whereas to be correct it must be in reverse depth order. The artifacts are the result of nonatomic rendering--the rendering has stripes because the execution of different threads is interleaved, whereas each layer of rendering should be dependent on the previous layer.
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kkz
To further clarify, some stripes appear solid green because the thread responsible for that portion of the image has essentially "overridden" concurrent contributions (by red, blue circles) due to the non-atomicity of the the pixel-write operation.
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sss
Could someone clarify for me whether the second picture here (the square one) is the same algorithm that is trying to draw the 3 circles (and failing artistically), or another one just to demonstrate interleaving.
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bxb
@sss The square photo is an example of 10K random circles drawn "correctly" (ie. preserving ordering and atomicity).
The trivially parallel renderer fails on a number of levels. The color of the circle intersections are incorrect because the color rendering is done in the incorrect order--in fact, it's entirely non-deterministic, whereas to be correct it must be in reverse depth order. The artifacts are the result of nonatomic rendering--the rendering has stripes because the execution of different threads is interleaved, whereas each layer of rendering should be dependent on the previous layer.
This comment was marked helpful 0 times.
To further clarify, some stripes appear solid green because the thread responsible for that portion of the image has essentially "overridden" concurrent contributions (by red, blue circles) due to the non-atomicity of the the pixel-write operation.
This comment was marked helpful 0 times.
Could someone clarify for me whether the second picture here (the square one) is the same algorithm that is trying to draw the 3 circles (and failing artistically), or another one just to demonstrate interleaving.
This comment was marked helpful 0 times.
@sss The square photo is an example of 10K random circles drawn "correctly" (ie. preserving ordering and atomicity).
This comment was marked helpful 0 times.