1 /*
2 * Mesa 3-D graphics library
3 * Version: 6.5.2
4 *
5 * Copyright (C) 1999-2006 Brian Paul All Rights Reserved.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a
8 * copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation
10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 * and/or sell copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included
15 * in all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
18 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
21 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
22 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23 */
24
25 /**
26 * \file swrast/s_alpha.c
27 * \brief Functions to apply alpha test.
28 */
29
30 #include "main/glheader.h"
31 #include "main/context.h"
32 #include "main/colormac.h"
33 #include "main/macros.h"
34
35 #include "s_alpha.h"
36 #include "s_context.h"
37
38
39 #define ALPHA_TEST(ALPHA, LOOP_CODE) \
40 do { \
41 switch (ctx->Color.AlphaFunc) { \
42 case GL_LESS: \
43 for (i = 0; i < n; i++) { \
44 mask[i] &= (ALPHA < ref); \
45 LOOP_CODE; \
46 } \
47 break; \
48 case GL_LEQUAL: \
49 for (i = 0; i < n; i++) { \
50 mask[i] &= (ALPHA <= ref); \
51 LOOP_CODE; \
52 } \
53 break; \
54 case GL_GEQUAL: \
55 for (i = 0; i < n; i++) { \
56 mask[i] &= (ALPHA >= ref); \
57 LOOP_CODE; \
58 } \
59 break; \
60 case GL_GREATER: \
61 for (i = 0; i < n; i++) { \
62 mask[i] &= (ALPHA > ref); \
63 LOOP_CODE; \
64 } \
65 break; \
66 case GL_NOTEQUAL: \
67 for (i = 0; i < n; i++) { \
68 mask[i] &= (ALPHA != ref); \
69 LOOP_CODE; \
70 } \
71 break; \
72 case GL_EQUAL: \
73 for (i = 0; i < n; i++) { \
74 mask[i] &= (ALPHA == ref); \
75 LOOP_CODE; \
76 } \
77 break; \
78 default: \
79 _mesa_problem(ctx, "Invalid alpha test in _swrast_alpha_test" ); \
80 return 0; \
81 } \
82 } while (0)
83
84
85
86 /**
87 * Perform the alpha test for an array of pixels.
88 * For pixels that fail the test, mask[i] will be set to 0.
89 * \return 0 if all pixels in the span failed the alpha test,
90 * 1 if one or more pixels passed the alpha test.
91 */
92 GLint
_swrast_alpha_test(const struct gl_context * ctx,SWspan * span)93 _swrast_alpha_test(const struct gl_context *ctx, SWspan *span)
94 {
95 const GLuint n = span->end;
96 GLubyte *mask = span->array->mask;
97 GLuint i;
98
99 if (ctx->Color.AlphaFunc == GL_ALWAYS) {
100 /* do nothing */
101 return 1;
102 }
103 else if (ctx->Color.AlphaFunc == GL_NEVER) {
104 /* All pixels failed - caller should check for this return value and
105 * act accordingly.
106 */
107 span->writeAll = GL_FALSE;
108 return 0;
109 }
110
111 if (span->arrayMask & SPAN_RGBA) {
112 /* Use array's alpha values */
113 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
114 GLubyte (*rgba)[4] = span->array->rgba8;
115 GLubyte ref;
116 CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
117 ALPHA_TEST(rgba[i][ACOMP], ;);
118 }
119 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
120 GLushort (*rgba)[4] = span->array->rgba16;
121 GLushort ref;
122 CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
123 ALPHA_TEST(rgba[i][ACOMP], ;);
124 }
125 else {
126 GLfloat (*rgba)[4] = span->array->attribs[FRAG_ATTRIB_COL0];
127 const GLfloat ref = ctx->Color.AlphaRef;
128 ALPHA_TEST(rgba[i][ACOMP], ;);
129 }
130 }
131 else {
132 /* Interpolate alpha values */
133 ASSERT(span->interpMask & SPAN_RGBA);
134 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
135 const GLfixed alphaStep = span->alphaStep;
136 GLfixed alpha = span->alpha;
137 GLubyte ref;
138 CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
139 ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
140 }
141 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
142 const GLfixed alphaStep = span->alphaStep;
143 GLfixed alpha = span->alpha;
144 GLushort ref;
145 CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
146 ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
147 }
148 else {
149 const GLfloat alphaStep = FixedToFloat(span->alphaStep);
150 GLfloat alpha = FixedToFloat(span->alpha);
151 const GLfloat ref = ctx->Color.AlphaRef;
152 ALPHA_TEST(alpha, alpha += alphaStep);
153 }
154 }
155
156 span->writeAll = GL_FALSE;
157
158 /* XXX examine mask[] values? */
159 return 1;
160 }
161