1 /*
2 * Mesa 3-D graphics library
3 *
4 * Copyright (C) 1999-2006 Brian Paul All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included
14 * in all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
17 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
20 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22 * 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/macros.h"
33
34 #include "s_alpha.h"
35 #include "s_context.h"
36
37
38 #define ALPHA_TEST(ALPHA, LOOP_CODE) \
39 do { \
40 switch (ctx->Color.AlphaFunc) { \
41 case GL_LESS: \
42 for (i = 0; i < n; i++) { \
43 mask[i] &= (ALPHA < ref); \
44 LOOP_CODE; \
45 } \
46 break; \
47 case GL_LEQUAL: \
48 for (i = 0; i < n; i++) { \
49 mask[i] &= (ALPHA <= ref); \
50 LOOP_CODE; \
51 } \
52 break; \
53 case GL_GEQUAL: \
54 for (i = 0; i < n; i++) { \
55 mask[i] &= (ALPHA >= ref); \
56 LOOP_CODE; \
57 } \
58 break; \
59 case GL_GREATER: \
60 for (i = 0; i < n; i++) { \
61 mask[i] &= (ALPHA > ref); \
62 LOOP_CODE; \
63 } \
64 break; \
65 case GL_NOTEQUAL: \
66 for (i = 0; i < n; i++) { \
67 mask[i] &= (ALPHA != ref); \
68 LOOP_CODE; \
69 } \
70 break; \
71 case GL_EQUAL: \
72 for (i = 0; i < n; i++) { \
73 mask[i] &= (ALPHA == ref); \
74 LOOP_CODE; \
75 } \
76 break; \
77 default: \
78 _mesa_problem(ctx, "Invalid alpha test in _swrast_alpha_test" ); \
79 return 0; \
80 } \
81 } while (0)
82
83
84
85 /**
86 * Perform the alpha test for an array of pixels.
87 * For pixels that fail the test, mask[i] will be set to 0.
88 * \return 0 if all pixels in the span failed the alpha test,
89 * 1 if one or more pixels passed the alpha test.
90 */
91 GLint
_swrast_alpha_test(const struct gl_context * ctx,SWspan * span)92 _swrast_alpha_test(const struct gl_context *ctx, SWspan *span)
93 {
94 const GLuint n = span->end;
95 GLubyte *mask = span->array->mask;
96 GLuint i;
97
98 if (ctx->Color.AlphaFunc == GL_ALWAYS) {
99 /* do nothing */
100 return 1;
101 }
102 else if (ctx->Color.AlphaFunc == GL_NEVER) {
103 /* All pixels failed - caller should check for this return value and
104 * act accordingly.
105 */
106 span->writeAll = GL_FALSE;
107 return 0;
108 }
109
110 if (span->arrayMask & SPAN_RGBA) {
111 /* Use array's alpha values */
112 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
113 GLubyte (*rgba)[4] = span->array->rgba8;
114 GLubyte ref;
115 CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
116 ALPHA_TEST(rgba[i][ACOMP], ;);
117 }
118 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
119 GLushort (*rgba)[4] = span->array->rgba16;
120 GLushort ref;
121 CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
122 ALPHA_TEST(rgba[i][ACOMP], ;);
123 }
124 else {
125 GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
126 const GLfloat ref = ctx->Color.AlphaRef;
127 ALPHA_TEST(rgba[i][ACOMP], ;);
128 }
129 }
130 else {
131 /* Interpolate alpha values */
132 assert(span->interpMask & SPAN_RGBA);
133 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
134 const GLfixed alphaStep = span->alphaStep;
135 GLfixed alpha = span->alpha;
136 GLubyte ref;
137 CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
138 ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
139 }
140 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
141 const GLfixed alphaStep = span->alphaStep;
142 GLfixed alpha = span->alpha;
143 GLushort ref;
144 CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
145 ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
146 }
147 else {
148 const GLfloat alphaStep = FixedToFloat(span->alphaStep);
149 GLfloat alpha = FixedToFloat(span->alpha);
150 const GLfloat ref = ctx->Color.AlphaRef;
151 ALPHA_TEST(alpha, alpha += alphaStep);
152 }
153 }
154
155 span->writeAll = GL_FALSE;
156
157 /* XXX examine mask[] values? */
158 return 1;
159 }
160