t_vb_fog.c revision ae0eaf93e092ac8e8b1c98f3e986de96940663fa 
1
2/*
3 * Mesa 3-D graphics library
4 * Version:  5.1
5 *
6 * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
7 *
8 * Permission is hereby granted, free of charge, to any person obtaining a
9 * copy of this software and associated documentation files (the "Software"),
10 * to deal in the Software without restriction, including without limitation
11 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
12 * and/or sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following conditions:
14 *
15 * The above copyright notice and this permission notice shall be included
16 * in all copies or substantial portions of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
21 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
22 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
23 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24 *
25 * Authors:
26 *    Keith Whitwell <keith@tungstengraphics.com>
27 */
28
29
30#include "glheader.h"
31#include "colormac.h"
32#include "context.h"
33#include "macros.h"
34#include "imports.h"
35#include "mtypes.h"
36
37#include "math/m_xform.h"
38
39#include "t_context.h"
40#include "t_pipeline.h"
41
42
43struct fog_stage_data {
44   GLvector4f fogcoord;		/* has actual storage allocated */
45   GLvector4f input;		/* points into VB->EyePtr Z values */
46};
47
48#define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
49
50#define FOG_EXP_TABLE_SIZE 256
51#define FOG_MAX (10.0)
52#define EXP_FOG_MAX .0006595
53#define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
54static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
55static GLfloat inited = 0;
56
57#if 1
58#define NEG_EXP( result, narg )						\
59do {									\
60   GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));			\
61   GLint k = (GLint) f;							\
62   if (k > FOG_EXP_TABLE_SIZE-2) 					\
63      result = (GLfloat) EXP_FOG_MAX;					\
64   else									\
65      result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);	\
66} while (0)
67#else
68#define NEG_EXP( result, narg )					\
69do {								\
70   result = exp(-narg);						\
71} while (0)
72#endif
73
74
75static void init_static_data( void )
76{
77   GLfloat f = 0.0F;
78   GLint i = 0;
79   for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
80      exp_table[i] = (GLfloat) exp(-f);
81   }
82   inited = 1;
83}
84
85
86static void make_win_fog_coords( GLcontext *ctx, GLvector4f *out,
87				 const GLvector4f *in )
88{
89   GLfloat end  = ctx->Fog.End;
90   GLfloat *v = in->start;
91   GLuint stride = in->stride;
92   GLuint n = in->count;
93   GLfloat (*data)[4] = out->data;
94   GLfloat d;
95   GLuint i;
96
97   out->count = in->count;
98
99   switch (ctx->Fog.Mode) {
100   case GL_LINEAR:
101      if (ctx->Fog.Start == ctx->Fog.End)
102         d = 1.0F;
103      else
104         d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
105      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
106         GLfloat f = (end - FABSF(*v)) * d;
107	 data[i][0] = CLAMP(f, 0.0F, 1.0F);
108      }
109      break;
110   case GL_EXP:
111      d = ctx->Fog.Density;
112      for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride))
113         NEG_EXP( data[i][0], d * FABSF(*v) );
114      break;
115   case GL_EXP2:
116      d = ctx->Fog.Density*ctx->Fog.Density;
117      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
118         GLfloat z = *v;
119         NEG_EXP( data[i][0], d * z * z );
120      }
121      break;
122   default:
123      _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
124      return;
125   }
126}
127
128
129static GLboolean run_fog_stage( GLcontext *ctx,
130				struct tnl_pipeline_stage *stage )
131{
132   struct vertex_buffer *VB = &TNL_CONTEXT(ctx)->vb;
133   struct fog_stage_data *store = FOG_STAGE_DATA(stage);
134   GLvector4f *input;
135
136   if (stage->changed_inputs == 0)
137      return GL_TRUE;
138
139   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {
140      /* fog computed from Z depth */
141      /* source = VB->ObjPtr or VB->EyePtr coords */
142      /* dest = VB->FogCoordPtr = fog stage private storage */
143      VB->FogCoordPtr = &store->fogcoord;
144
145      if (!ctx->_NeedEyeCoords) {
146	 const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
147	 GLfloat plane[4];
148
149	 /* Use this to store calculated eye z values:
150	  */
151	 input = &store->fogcoord;
152
153	 plane[0] = m[2];
154	 plane[1] = m[6];
155	 plane[2] = m[10];
156	 plane[3] = m[14];
157
158	 /* Full eye coords weren't required, just calculate the
159	  * eye Z values.
160	  */
161	 _mesa_dotprod_tab[VB->ObjPtr->size]( (GLfloat *) input->data,
162					      4 * sizeof(GLfloat),
163					      VB->ObjPtr, plane );
164
165	 input->count = VB->ObjPtr->count;
166      }
167      else {
168	 input = &store->input;
169
170	 if (VB->EyePtr->size < 2)
171	    _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
172
173	 input->data = (GLfloat (*)[4]) &(VB->EyePtr->data[0][2]);
174	 input->start = VB->EyePtr->start+2;
175	 input->stride = VB->EyePtr->stride;
176	 input->count = VB->EyePtr->count;
177      }
178   }
179   else {
180      /* use glFogCoord() coordinates */
181      /* source = VB->FogCoordPtr */
182      input = VB->FogCoordPtr;
183      /* dest = fog stage private storage */
184      VB->FogCoordPtr = &store->fogcoord;
185   }
186
187   make_win_fog_coords( ctx, VB->FogCoordPtr, input );
188   return GL_TRUE;
189}
190
191
192static void check_fog_stage( GLcontext *ctx, struct tnl_pipeline_stage *stage )
193{
194   stage->active = ctx->Fog.Enabled && !ctx->VertexProgram.Enabled;
195
196   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT)
197      stage->inputs = _TNL_BIT_POS;
198   else
199      stage->inputs = _TNL_BIT_FOG;
200}
201
202
203/* Called the first time stage->run() is invoked.
204 */
205static GLboolean alloc_fog_data( GLcontext *ctx,
206				 struct tnl_pipeline_stage *stage )
207{
208   TNLcontext *tnl = TNL_CONTEXT(ctx);
209   struct fog_stage_data *store;
210   stage->privatePtr = MALLOC(sizeof(*store));
211   store = FOG_STAGE_DATA(stage);
212   if (!store)
213      return GL_FALSE;
214
215   _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
216   _mesa_vector4f_init( &store->input, 0, 0 );
217
218   if (!inited)
219      init_static_data();
220
221   /* Now run the stage.
222    */
223   stage->run = run_fog_stage;
224   return stage->run( ctx, stage );
225}
226
227
228static void free_fog_data( struct tnl_pipeline_stage *stage )
229{
230   struct fog_stage_data *store = FOG_STAGE_DATA(stage);
231   if (store) {
232      _mesa_vector4f_free( &store->fogcoord );
233      FREE( store );
234      stage->privatePtr = NULL;
235   }
236}
237
238
239const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
240{
241   "build fog coordinates",	/* name */
242   _NEW_FOG,			/* check_state */
243   _NEW_FOG,			/* run_state */
244   GL_FALSE,			/* active? */
245   0,				/* inputs */
246   _TNL_BIT_FOG,		/* outputs */
247   0,				/* changed_inputs */
248   NULL,			/* private_data */
249   free_fog_data,		/* dtr */
250   check_fog_stage,		/* check */
251   alloc_fog_data		/* run -- initially set to init. */
252};
253