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 * Authors:
25 * Keith Whitwell <keithw@vmware.com>
26 */
27
28
29 #include "c99_math.h"
30 #include "main/errors.h"
31 #include "main/glheader.h"
32 #include "main/macros.h"
33
34 #include "main/mtypes.h"
35
36 #include "math/m_xform.h"
37
38 #include "t_context.h"
39 #include "t_pipeline.h"
40
41
42 struct fog_stage_data {
43 GLvector4f fogcoord; /* has actual storage allocated */
44 };
45
46 #define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
47
48 #define FOG_EXP_TABLE_SIZE 256
49 #define FOG_MAX (10.0F)
50 #define EXP_FOG_MAX .0006595F
51 #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
52 static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
53 static GLfloat inited = 0;
54
55 #if 1
56 #define NEG_EXP( result, narg ) \
57 do { \
58 GLfloat f = (GLfloat) (narg * (1.0F / FOG_INCR)); \
59 GLint k = (GLint) f; \
60 if (k > FOG_EXP_TABLE_SIZE-2) \
61 result = (GLfloat) EXP_FOG_MAX; \
62 else \
63 result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]); \
64 } while (0)
65 #else
66 #define NEG_EXP( result, narg ) \
67 do { \
68 result = exp(-narg); \
69 } while (0)
70 #endif
71
72
73 /**
74 * Initialize the exp_table[] lookup table for approximating exp().
75 */
76 static void
init_static_data(void)77 init_static_data( void )
78 {
79 GLfloat f = 0.0F;
80 GLint i = 0;
81 for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
82 exp_table[i] = expf(-f);
83 }
84 inited = 1;
85 }
86
87
88 /**
89 * Compute per-vertex fog blend factors from fog coordinates by
90 * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
91 * Fog coordinates are distances from the eye (typically between the
92 * near and far clip plane distances).
93 * Note that fogcoords may be negative, if eye z is source absolute
94 * value must be taken earlier.
95 * Fog blend factors are in the range [0,1].
96 */
97 static void
compute_fog_blend_factors(struct gl_context * ctx,GLvector4f * out,const GLvector4f * in)98 compute_fog_blend_factors(struct gl_context *ctx, GLvector4f *out, const GLvector4f *in)
99 {
100 GLfloat end = ctx->Fog.End;
101 GLfloat *v = in->start;
102 GLuint stride = in->stride;
103 GLuint n = in->count;
104 GLfloat (*data)[4] = out->data;
105 GLfloat d;
106 GLuint i;
107
108 out->count = in->count;
109
110 switch (ctx->Fog.Mode) {
111 case GL_LINEAR:
112 if (ctx->Fog.Start == ctx->Fog.End)
113 d = 1.0F;
114 else
115 d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
116 for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
117 const GLfloat z = *v;
118 GLfloat f = (end - z) * d;
119 data[i][0] = CLAMP(f, 0.0F, 1.0F);
120 }
121 break;
122 case GL_EXP:
123 d = ctx->Fog.Density;
124 for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
125 const GLfloat z = *v;
126 NEG_EXP( data[i][0], d * z );
127 }
128 break;
129 case GL_EXP2:
130 d = ctx->Fog.Density*ctx->Fog.Density;
131 for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
132 const GLfloat z = *v;
133 NEG_EXP( data[i][0], d * z * z );
134 }
135 break;
136 default:
137 _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
138 return;
139 }
140 }
141
142
143 static GLboolean
run_fog_stage(struct gl_context * ctx,struct tnl_pipeline_stage * stage)144 run_fog_stage(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
145 {
146 TNLcontext *tnl = TNL_CONTEXT(ctx);
147 struct vertex_buffer *VB = &tnl->vb;
148 struct fog_stage_data *store = FOG_STAGE_DATA(stage);
149 GLvector4f *input;
150
151
152 if (!ctx->Fog.Enabled)
153 return GL_TRUE;
154
155 if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT && !ctx->VertexProgram._Current) {
156 GLuint i;
157 GLfloat *coord;
158 /* Fog is computed from vertex or fragment Z values */
159 /* source = VB->AttribPtr[_TNL_ATTRIB_POS] or VB->EyePtr coords */
160 /* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
161 VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;
162
163 if (!ctx->_NeedEyeCoords) {
164 /* compute fog coords from object coords */
165 const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
166 GLfloat plane[4];
167
168 /* Use this to store calculated eye z values:
169 */
170 input = &store->fogcoord;
171
172 plane[0] = m[2];
173 plane[1] = m[6];
174 plane[2] = m[10];
175 plane[3] = m[14];
176 /* Full eye coords weren't required, just calculate the
177 * eye Z values.
178 */
179 _mesa_dotprod_tab[VB->AttribPtr[_TNL_ATTRIB_POS]->size]
180 ( (GLfloat *) input->data,
181 4 * sizeof(GLfloat),
182 VB->AttribPtr[_TNL_ATTRIB_POS], plane );
183
184 input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
185
186 /* make sure coords are really positive
187 NOTE should avoid going through array twice */
188 coord = input->start;
189 for (i = 0; i < input->count; i++) {
190 *coord = fabsf(*coord);
191 STRIDE_F(coord, input->stride);
192 }
193 }
194 else {
195 /* fog coordinates = eye Z coordinates - need to copy for ABS */
196 input = &store->fogcoord;
197
198 if (VB->EyePtr->size < 2)
199 _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
200
201 input->stride = 4 * sizeof(GLfloat);
202 input->count = VB->EyePtr->count;
203 coord = VB->EyePtr->start;
204 for (i = 0 ; i < VB->EyePtr->count; i++) {
205 input->data[i][0] = fabsf(coord[2]);
206 STRIDE_F(coord, VB->EyePtr->stride);
207 }
208 }
209 }
210 else {
211 /* use glFogCoord() coordinates */
212 input = VB->AttribPtr[_TNL_ATTRIB_FOG]; /* source data */
213
214 /* input->count may be one if glFogCoord was only called once
215 * before glBegin. But we need to compute fog for all vertices.
216 */
217 input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
218
219 VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord; /* dest data */
220 }
221
222 if (tnl->_DoVertexFog) {
223 /* compute blend factors from fog coordinates */
224 compute_fog_blend_factors( ctx, VB->AttribPtr[_TNL_ATTRIB_FOG], input );
225 }
226 else {
227 /* results = incoming fog coords (compute fog per-fragment later) */
228 VB->AttribPtr[_TNL_ATTRIB_FOG] = input;
229 }
230
231 return GL_TRUE;
232 }
233
234
235
236 /* Called the first time stage->run() is invoked.
237 */
238 static GLboolean
alloc_fog_data(struct gl_context * ctx,struct tnl_pipeline_stage * stage)239 alloc_fog_data(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
240 {
241 TNLcontext *tnl = TNL_CONTEXT(ctx);
242 struct fog_stage_data *store;
243 stage->privatePtr = malloc(sizeof(*store));
244 store = FOG_STAGE_DATA(stage);
245 if (!store)
246 return GL_FALSE;
247
248 _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
249
250 if (!inited)
251 init_static_data();
252
253 return GL_TRUE;
254 }
255
256
257 static void
free_fog_data(struct tnl_pipeline_stage * stage)258 free_fog_data(struct tnl_pipeline_stage *stage)
259 {
260 struct fog_stage_data *store = FOG_STAGE_DATA(stage);
261 if (store) {
262 _mesa_vector4f_free( &store->fogcoord );
263 free( store );
264 stage->privatePtr = NULL;
265 }
266 }
267
268
269 const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
270 {
271 "build fog coordinates", /* name */
272 NULL, /* private_data */
273 alloc_fog_data, /* dtr */
274 free_fog_data, /* dtr */
275 NULL, /* check */
276 run_fog_stage /* run -- initially set to init. */
277 };
278