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glReadPixels & alpha channel problem

Graphics and GPU Programming Programming

Started by TM September 05, 2001 10:47 AM

3 comments, last by TM 22 years, 7 months ago

122

Author

September 05, 2001 10:47 AM

I''m trying to read RGBA colors from the frame buffer using glReadPixels, but all my alpha''s are 255. Anyone encountered this problem before?

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zedzeek

529

September 05, 2001 04:24 PM

does your card support destination alpha?
is your window created with destination alpha?
are u sure the alpha values of the pixels u read aint 255?

Captain Courgette, eat more veg

122

Author

September 06, 2001 02:08 AM

yes
yes
yes

122

Author

September 06, 2001 02:57 AM

Shit, got it!

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_ALPHA | GLUT_DEPTH | GLUT_STENCIL);

instead of

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);

Damn!

zedzeek

529

September 06, 2001 04:53 PM

so it was
yes
no
yes

watch out not all cards support destination alpha, though i believe only the very old/bad ones dont

Captain Courgette, eat more veg

This topic is closed to new replies.

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