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 #include "c99_math.h"
27 #include "main/glheader.h"
28 #include "main/macros.h"
29
30 #include "s_context.h"
31 #include "s_fog.h"
32
33
34 /**
35 * Used to convert current raster distance to a fog factor in [0,1].
36 */
37 GLfloat
_swrast_z_to_fogfactor(struct gl_context * ctx,GLfloat z)38 _swrast_z_to_fogfactor(struct gl_context *ctx, GLfloat z)
39 {
40 GLfloat d, f;
41
42 switch (ctx->Fog.Mode) {
43 case GL_LINEAR:
44 if (ctx->Fog.Start == ctx->Fog.End)
45 d = 1.0F;
46 else
47 d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
48 f = (ctx->Fog.End - z) * d;
49 return CLAMP(f, 0.0F, 1.0F);
50 case GL_EXP:
51 d = ctx->Fog.Density;
52 f = expf(-d * z);
53 f = CLAMP(f, 0.0F, 1.0F);
54 return f;
55 case GL_EXP2:
56 d = ctx->Fog.Density;
57 f = expf(-(d * d * z * z));
58 f = CLAMP(f, 0.0F, 1.0F);
59 return f;
60 default:
61 _mesa_problem(ctx, "Bad fog mode in _swrast_z_to_fogfactor");
62 return 0.0;
63 }
64 }
65
66
67 #define LINEAR_FOG(f, coord) f = (fogEnd - coord) * fogScale
68
69 #define EXP_FOG(f, coord) f = expf(density * coord)
70
71 #define EXP2_FOG(f, coord) \
72 do { \
73 GLfloat tmp = negDensitySquared * coord * coord; \
74 if (tmp < FLT_MIN_10_EXP) \
75 tmp = FLT_MIN_10_EXP; \
76 f = expf(tmp); \
77 } while(0)
78
79
80 #define BLEND_FOG(f, coord) f = coord
81
82
83
84 /**
85 * Template code for computing fog blend factor and applying it to colors.
86 * \param TYPE either GLubyte, GLushort or GLfloat.
87 * \param COMPUTE_F code to compute the fog blend factor, f.
88 */
89 #define FOG_LOOP(TYPE, FOG_FUNC) \
90 if (span->arrayAttribs & VARYING_BIT_FOGC) { \
91 GLuint i; \
92 for (i = 0; i < span->end; i++) { \
93 const GLfloat fogCoord = span->array->attribs[VARYING_SLOT_FOGC][i][0]; \
94 const GLfloat c = fabsf(fogCoord); \
95 GLfloat f, oneMinusF; \
96 FOG_FUNC(f, c); \
97 f = CLAMP(f, 0.0F, 1.0F); \
98 oneMinusF = 1.0F - f; \
99 rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog); \
100 rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog); \
101 rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog); \
102 } \
103 } \
104 else { \
105 const GLfloat fogStep = span->attrStepX[VARYING_SLOT_FOGC][0]; \
106 GLfloat fogCoord = span->attrStart[VARYING_SLOT_FOGC][0]; \
107 const GLfloat wStep = span->attrStepX[VARYING_SLOT_POS][3]; \
108 GLfloat w = span->attrStart[VARYING_SLOT_POS][3]; \
109 GLuint i; \
110 for (i = 0; i < span->end; i++) { \
111 const GLfloat c = fabsf(fogCoord) / w; \
112 GLfloat f, oneMinusF; \
113 FOG_FUNC(f, c); \
114 f = CLAMP(f, 0.0F, 1.0F); \
115 oneMinusF = 1.0F - f; \
116 rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog); \
117 rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog); \
118 rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog); \
119 fogCoord += fogStep; \
120 w += wStep; \
121 } \
122 }
123
124 /**
125 * Apply fog to a span of RGBA pixels.
126 * The fog value are either in the span->array->fog array or interpolated from
127 * the fog/fogStep values.
128 * They fog values are either fog coordinates (Z) or fog blend factors.
129 * _PreferPixelFog should be in sync with that state!
130 */
131 void
_swrast_fog_rgba_span(const struct gl_context * ctx,SWspan * span)132 _swrast_fog_rgba_span( const struct gl_context *ctx, SWspan *span )
133 {
134 const SWcontext *swrast = CONST_SWRAST_CONTEXT(ctx);
135 GLfloat rFog, gFog, bFog;
136
137 assert(swrast->_FogEnabled);
138 assert(span->arrayMask & SPAN_RGBA);
139
140 /* compute (scaled) fog color */
141 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
142 rFog = ctx->Fog.Color[RCOMP] * 255.0F;
143 gFog = ctx->Fog.Color[GCOMP] * 255.0F;
144 bFog = ctx->Fog.Color[BCOMP] * 255.0F;
145 }
146 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
147 rFog = ctx->Fog.Color[RCOMP] * 65535.0F;
148 gFog = ctx->Fog.Color[GCOMP] * 65535.0F;
149 bFog = ctx->Fog.Color[BCOMP] * 65535.0F;
150 }
151 else {
152 rFog = ctx->Fog.Color[RCOMP];
153 gFog = ctx->Fog.Color[GCOMP];
154 bFog = ctx->Fog.Color[BCOMP];
155 }
156
157 if (swrast->_PreferPixelFog) {
158 /* The span's fog values are fog coordinates, now compute blend factors
159 * and blend the fragment colors with the fog color.
160 */
161 switch (ctx->Fog.Mode) {
162 case GL_LINEAR:
163 {
164 const GLfloat fogEnd = ctx->Fog.End;
165 const GLfloat fogScale = (ctx->Fog.Start == ctx->Fog.End)
166 ? 1.0F : 1.0F / (ctx->Fog.End - ctx->Fog.Start);
167 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
168 GLubyte (*rgba)[4] = span->array->rgba8;
169 FOG_LOOP(GLubyte, LINEAR_FOG);
170 }
171 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
172 GLushort (*rgba)[4] = span->array->rgba16;
173 FOG_LOOP(GLushort, LINEAR_FOG);
174 }
175 else {
176 GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
177 assert(span->array->ChanType == GL_FLOAT);
178 FOG_LOOP(GLfloat, LINEAR_FOG);
179 }
180 }
181 break;
182
183 case GL_EXP:
184 {
185 const GLfloat density = -ctx->Fog.Density;
186 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
187 GLubyte (*rgba)[4] = span->array->rgba8;
188 FOG_LOOP(GLubyte, EXP_FOG);
189 }
190 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
191 GLushort (*rgba)[4] = span->array->rgba16;
192 FOG_LOOP(GLushort, EXP_FOG);
193 }
194 else {
195 GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
196 assert(span->array->ChanType == GL_FLOAT);
197 FOG_LOOP(GLfloat, EXP_FOG);
198 }
199 }
200 break;
201
202 case GL_EXP2:
203 {
204 const GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
205 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
206 GLubyte (*rgba)[4] = span->array->rgba8;
207 FOG_LOOP(GLubyte, EXP2_FOG);
208 }
209 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
210 GLushort (*rgba)[4] = span->array->rgba16;
211 FOG_LOOP(GLushort, EXP2_FOG);
212 }
213 else {
214 GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
215 assert(span->array->ChanType == GL_FLOAT);
216 FOG_LOOP(GLfloat, EXP2_FOG);
217 }
218 }
219 break;
220
221 default:
222 _mesa_problem(ctx, "Bad fog mode in _swrast_fog_rgba_span");
223 return;
224 }
225 }
226 else {
227 /* The span's fog start/step/array values are blend factors in [0,1].
228 * They were previously computed per-vertex.
229 */
230 if (span->array->ChanType == GL_UNSIGNED_BYTE) {
231 GLubyte (*rgba)[4] = span->array->rgba8;
232 FOG_LOOP(GLubyte, BLEND_FOG);
233 }
234 else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
235 GLushort (*rgba)[4] = span->array->rgba16;
236 FOG_LOOP(GLushort, BLEND_FOG);
237 }
238 else {
239 GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
240 assert(span->array->ChanType == GL_FLOAT);
241 FOG_LOOP(GLfloat, BLEND_FOG);
242 }
243 }
244 }
245