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