t_vb_fog.c revision 27558a160a9fe91745728d7626995cd88f8fe339 
1/* $Id: t_vb_fog.c,v 1.20 2003/03/01 01:50:27 brianp Exp $ */
2
3/*
4 * Mesa 3-D graphics library
5 * Version:  5.1
6 *
7 * Copyright (C) 1999-2003  Brian Paul   All Rights Reserved.
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
15 *
16 * The above copyright notice and this permission notice shall be included
17 * in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
20 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
22 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
23 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
24 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 * Authors:
27 *    Keith Whitwell <keith@tungstengraphics.com>
28 */
29
30
31#include "glheader.h"
32#include "colormac.h"
33#include "context.h"
34#include "macros.h"
35#include "imports.h"
36#include "mtypes.h"
37
38#include "math/m_xform.h"
39
40#include "t_context.h"
41#include "t_pipeline.h"
42
43
44struct fog_stage_data {
45   GLvector4f fogcoord;		/* has actual storage allocated */
46   GLvector4f input;		/* points into VB->EyePtr Z values */
47};
48
49#define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
50
51#define FOG_EXP_TABLE_SIZE 256
52#define FOG_MAX (10.0)
53#define EXP_FOG_MAX .0006595
54#define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
55static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
56static GLfloat inited = 0;
57
58#if 1
59#define NEG_EXP( result, narg )						\
60do {									\
61   GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));			\
62   GLint k = (GLint) f;							\
63   if (k > FOG_EXP_TABLE_SIZE-2) 					\
64      result = (GLfloat) EXP_FOG_MAX;					\
65   else									\
66      result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);	\
67} while (0)
68#else
69#define NEG_EXP( result, narg )					\
70do {								\
71   result = exp(-narg);						\
72} while (0)
73#endif
74
75
76static void 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] = (GLfloat) exp(-f);
82   }
83   inited = 1;
84}
85
86
87static void make_win_fog_coords( GLcontext *ctx, GLvector4f *out,
88				 const GLvector4f *in )
89{
90   GLfloat end  = ctx->Fog.End;
91   GLfloat *v = in->start;
92   GLuint stride = in->stride;
93   GLuint n = in->count;
94   GLfloat (*data)[4] = out->data;
95   GLfloat d;
96   GLuint i;
97
98   out->count = in->count;
99
100   switch (ctx->Fog.Mode) {
101   case GL_LINEAR:
102      if (ctx->Fog.Start == ctx->Fog.End)
103         d = 1.0F;
104      else
105         d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
106      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
107         GLfloat f = (end - FABSF(*v)) * d;
108	 data[i][0] = CLAMP(f, 0.0F, 1.0F);
109      }
110      break;
111   case GL_EXP:
112      d = ctx->Fog.Density;
113      for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride))
114         NEG_EXP( data[i][0], d * FABSF(*v) );
115      break;
116   case GL_EXP2:
117      d = ctx->Fog.Density*ctx->Fog.Density;
118      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
119         GLfloat z = *v;
120         NEG_EXP( data[i][0], d * z * z );
121      }
122      break;
123   default:
124      _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
125      return;
126   }
127}
128
129
130static GLboolean run_fog_stage( GLcontext *ctx,
131				struct gl_pipeline_stage *stage )
132{
133   struct vertex_buffer *VB = &TNL_CONTEXT(ctx)->vb;
134   struct fog_stage_data *store = FOG_STAGE_DATA(stage);
135   GLvector4f *input;
136
137   if (stage->changed_inputs == 0)
138      return GL_TRUE;
139
140   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {
141      /* fog computed from Z depth */
142      /* source = VB->ObjPtr or VB->EyePtr coords */
143      /* dest = VB->FogCoordPtr = fog stage private storage */
144      VB->FogCoordPtr = &store->fogcoord;
145
146      if (!ctx->_NeedEyeCoords) {
147	 const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
148	 GLfloat plane[4];
149
150	 /* Use this to store calculated eye z values:
151	  */
152	 input = &store->fogcoord;
153
154	 plane[0] = m[2];
155	 plane[1] = m[6];
156	 plane[2] = m[10];
157	 plane[3] = m[14];
158
159	 /* Full eye coords weren't required, just calculate the
160	  * eye Z values.
161	  */
162	 _mesa_dotprod_tab[VB->ObjPtr->size]( (GLfloat *) input->data,
163					      4 * sizeof(GLfloat),
164					      VB->ObjPtr, plane );
165
166	 input->count = VB->ObjPtr->count;
167      }
168      else {
169	 input = &store->input;
170
171	 if (VB->EyePtr->size < 2)
172	    _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
173
174	 input->data = (GLfloat (*)[4]) &(VB->EyePtr->data[0][2]);
175	 input->start = VB->EyePtr->start+2;
176	 input->stride = VB->EyePtr->stride;
177	 input->count = VB->EyePtr->count;
178      }
179   }
180   else {
181      /* use glFogCoord() coordinates */
182      /* source = VB->FogCoordPtr */
183      input = VB->FogCoordPtr;
184      /* dest = fog stage private storage */
185      VB->FogCoordPtr = &store->fogcoord;
186   }
187
188   make_win_fog_coords( ctx, VB->FogCoordPtr, input );
189   return GL_TRUE;
190}
191
192
193static void check_fog_stage( GLcontext *ctx, struct gl_pipeline_stage *stage )
194{
195   stage->active = ctx->Fog.Enabled && !ctx->VertexProgram.Enabled;
196
197   if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT)
198      stage->inputs = VERT_BIT_EYE;
199   else
200      stage->inputs = VERT_BIT_FOG;
201}
202
203
204/* Called the first time stage->run() is invoked.
205 */
206static GLboolean alloc_fog_data( GLcontext *ctx,
207				 struct gl_pipeline_stage *stage )
208{
209   TNLcontext *tnl = TNL_CONTEXT(ctx);
210   struct fog_stage_data *store;
211   stage->privatePtr = MALLOC(sizeof(*store));
212   store = FOG_STAGE_DATA(stage);
213   if (!store)
214      return GL_FALSE;
215
216   _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
217   _mesa_vector4f_init( &store->input, 0, 0 );
218
219   if (!inited)
220      init_static_data();
221
222   /* Now run the stage.
223    */
224   stage->run = run_fog_stage;
225   return stage->run( ctx, stage );
226}
227
228
229static void free_fog_data( struct gl_pipeline_stage *stage )
230{
231   struct fog_stage_data *store = FOG_STAGE_DATA(stage);
232   if (store) {
233      _mesa_vector4f_free( &store->fogcoord );
234      FREE( store );
235      stage->privatePtr = NULL;
236   }
237}
238
239
240const struct gl_pipeline_stage _tnl_fog_coordinate_stage =
241{
242   "build fog coordinates",	/* name */
243   _NEW_FOG,			/* check_state */
244   _NEW_FOG,			/* run_state */
245   GL_FALSE,			/* active? */
246   0,				/* inputs */
247   VERT_BIT_FOG,		/* outputs */
248   0,				/* changed_inputs */
249   NULL,			/* private_data */
250   free_fog_data,		/* dtr */
251   check_fog_stage,		/* check */
252   alloc_fog_data		/* run -- initially set to init. */
253};
254