1 /* $Id: s_alpha.c,v 1.3 2001/03/03 20:33:30 brianp Exp $ */
4 * Mesa 3-D graphics library
7 * Copyright (C) 1999-2000 Brian Paul All Rights Reserved.
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10 * copy of this software and associated documentation files (the "Software"),
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14 * Software is furnished to do so, subject to the following conditions:
16 * The above copyright notice and this permission notice shall be included
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19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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41 * Apply the alpha test to a span of pixels.
42 * In: rgba - array of pixels
43 * In/Out: mask - current pixel mask. Pixels which fail the alpha test
44 * will set the corresponding mask flag to 0.
45 * Return: 0 = all pixels in the span failed the alpha test.
46 * 1 = one or more pixels passed the alpha test.
49 _mesa_alpha_test( const GLcontext
*ctx
,
50 GLuint n
, CONST GLchan rgba
[][4], GLubyte mask
[] )
53 GLchan ref
= ctx
->Color
.AlphaRef
;
55 /* switch cases ordered from most frequent to less frequent */
56 switch (ctx
->Color
.AlphaFunc
) {
59 mask
[i
] &= (rgba
[i
][ACOMP
] < ref
);
64 mask
[i
] &= (rgba
[i
][ACOMP
] <= ref
);
68 mask
[i
] &= (rgba
[i
][ACOMP
] >= ref
);
73 mask
[i
] &= (rgba
[i
][ACOMP
] > ref
);
78 mask
[i
] &= (rgba
[i
][ACOMP
] != ref
);
83 mask
[i
] &= (rgba
[i
][ACOMP
] == ref
);
90 /* caller should check for zero! */
93 _mesa_problem( ctx
, "Invalid alpha test in gl_alpha_test" );