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[566/906] effects: avoid using tanh in sin_fragment

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It produces weird results on nouveau.
Provide an alternative implementation with (1-sinh)*cosh
This commit is contained in:
Matthew Waters 2012-08-20 13:27:50 +10:00
parent 96163f1589
commit beff5a3710
1 changed files with 4 additions and 4 deletions
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8
gst/gl/effects/gstgleffectssources.c
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@ -458,7 +458,7 @@ const gchar *sin_fragment_source =
/* sqrt(3)/2 = 0.866 */ /* sqrt(3)/2 = 0.866 */
" float sinh = 0.866*(color.g - color.b);" " float sinh = 0.866*(color.g - color.b);"
/* hue = atan2 h */ /* hue = atan2 h */
" float tanh = sinh/cosh;" " float sch = (1.0-sinh)*cosh;"
/* ok this is a little trick I came up because I didn't find any /* ok this is a little trick I came up because I didn't find any
* detailed proof of the Preucil formula. The issue is that tan(h) is * detailed proof of the Preucil formula. The issue is that tan(h) is
* pi-periodic so the smoothstep thing gives both reds (h = 0) and * pi-periodic so the smoothstep thing gives both reds (h = 0) and
@ -467,9 +467,9 @@ const gchar *sin_fragment_source =
* the circle where cosine is positive */ * the circle where cosine is positive */
/* take a slightly purple color trying to get rid of human skin reds */ /* take a slightly purple color trying to get rid of human skin reds */
/* tanh = +-1.0 for h = +-45, where yellow=60, magenta=-60 */ /* tanh = +-1.0 for h = +-45, where yellow=60, magenta=-60 */
" float a = smoothstep (-1.0, -0.5, tanh);" " float a = smoothstep (0.3, 1.0, sch);"
" float b = smoothstep (-0.1, 0.4, tanh);" " float b = smoothstep (-0.4, -0.1, sinh);"
" float mix = (a - b) * step (0.0, cosh);" " float mix = a * b;"
" gl_FragColor = color * mix + luma * (1.0 - mix);" " gl_FragColor = color * mix + luma * (1.0 - mix);"
"}"; "}";