No, no, no! You’ve been repeatedly missing the fact that these 100 polygons may all be overlapping, and semi-transparent! It’s impossible to lump them together, the only way to render them is one at a time, in the original order!! The clip area is irrelevant![/quote]
It’s not an issue, is it ?
Concidering overlapping and semi transparent polygon, you’ll do that operation with only 2 textures (texture width = Sum of polygon width / texture height = Max polygon height):
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Draw polygon #1’s mask (that’s 100 px wide) on the topleft of a texture
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Draw polygon #2 mask start from 100px on the left, to the same texture
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Draw the image / stuff to the second texture the same way.
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In the final step, copy texture parts applying the blend/masking operations either through a shader, either with the obsolete GL API CopyTexture, in the same order as you’ve draw the polygon initially.
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Finally use the texture wherever you want to.