2 * Mesa 3-D graphics library
5 * Copyright (C) 1999-2004 Brian Paul All Rights Reserved.
7 * Permission is hereby granted, free of charge, to any person obtaining a
8 * copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation
10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 * and/or sell copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following conditions:
14 * The above copyright notice and this permission notice shall be included
15 * in all copies or substantial portions of the Software.
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
18 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
21 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
22 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 * Keith Whitwell <keith@tungstengraphics.com>
36 #include "math/m_xform.h"
38 #include "t_context.h"
39 #include "t_pipeline.h"
42 struct fog_stage_data
{
43 GLvector4f fogcoord
; /* has actual storage allocated */
44 GLvector4f input
; /* points into VB->EyePtr Z values */
47 #define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
49 #define FOG_EXP_TABLE_SIZE 256
50 #define FOG_MAX (10.0)
51 #define EXP_FOG_MAX .0006595
52 #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
53 static GLfloat exp_table
[FOG_EXP_TABLE_SIZE
];
54 static GLfloat inited
= 0;
57 #define NEG_EXP( result, narg ) \
59 GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR)); \
60 GLint k = (GLint) f; \
61 if (k > FOG_EXP_TABLE_SIZE-2) \
62 result = (GLfloat) EXP_FOG_MAX; \
64 result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]); \
67 #define NEG_EXP( result, narg ) \
69 result = exp(-narg); \
75 * Initialize the exp_table[] lookup table for approximating exp().
78 init_static_data( void )
82 for ( ; i
< FOG_EXP_TABLE_SIZE
; i
++, f
+= FOG_INCR
) {
83 exp_table
[i
] = (GLfloat
) exp(-f
);
90 * Compute per-vertex fog blend factors from fog coordinates by
91 * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
92 * Fog coordinates are distances from the eye (typically between the
93 * near and far clip plane distances).
94 * Note the fog (eye Z) coords may be negative so we use ABS(z) below.
95 * Fog blend factors are in the range [0,1].
98 compute_fog_blend_factors(GLcontext
*ctx
, GLvector4f
*out
, const GLvector4f
*in
)
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
;
108 out
->count
= in
->count
;
110 switch (ctx
->Fog
.Mode
) {
112 if (ctx
->Fog
.Start
== ctx
->Fog
.End
)
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
= FABSF(*v
);
118 GLfloat f
= (end
- z
) * d
;
119 data
[i
][0] = CLAMP(f
, 0.0F
, 1.0F
);
123 d
= ctx
->Fog
.Density
;
124 for ( i
= 0 ; i
< n
; i
++, STRIDE_F(v
,stride
)) {
125 const GLfloat z
= FABSF(*v
);
126 NEG_EXP( data
[i
][0], d
* z
);
130 d
= ctx
->Fog
.Density
*ctx
->Fog
.Density
;
131 for ( i
= 0 ; i
< n
; i
++, STRIDE_F(v
, stride
)) {
132 const GLfloat z
= FABSF(*v
);
133 NEG_EXP( data
[i
][0], d
* z
* z
);
137 _mesa_problem(ctx
, "Bad fog mode in make_fog_coord");
144 run_fog_stage(GLcontext
*ctx
, struct tnl_pipeline_stage
*stage
)
146 TNLcontext
*tnl
= TNL_CONTEXT(ctx
);
147 struct vertex_buffer
*VB
= &tnl
->vb
;
148 struct fog_stage_data
*store
= FOG_STAGE_DATA(stage
);
151 if (stage
->changed_inputs
== 0)
154 if (ctx
->Fog
.FogCoordinateSource
== GL_FRAGMENT_DEPTH_EXT
) {
155 /* Fog is computed from vertex or fragment Z values */
156 /* source = VB->ObjPtr or VB->EyePtr coords */
157 /* dest = VB->FogCoordPtr = fog stage private storage */
158 VB
->FogCoordPtr
= &store
->fogcoord
;
160 if (!ctx
->_NeedEyeCoords
) {
161 /* compute fog coords from object coords */
162 const GLfloat
*m
= ctx
->ModelviewMatrixStack
.Top
->m
;
165 /* Use this to store calculated eye z values:
167 input
= &store
->fogcoord
;
169 /* NOTE: negate plane here so we get positive fog coords! */
174 /* Full eye coords weren't required, just calculate the
177 _mesa_dotprod_tab
[VB
->ObjPtr
->size
]( (GLfloat
*) input
->data
,
181 input
->count
= VB
->ObjPtr
->count
;
184 /* fog coordinates = eye Z coordinates (use ABS later) */
185 input
= &store
->input
;
187 if (VB
->EyePtr
->size
< 2)
188 _mesa_vector4f_clean_elem( VB
->EyePtr
, VB
->Count
, 2 );
190 input
->data
= (GLfloat (*)[4]) &(VB
->EyePtr
->data
[0][2]);
191 input
->start
= VB
->EyePtr
->start
+2;
192 input
->stride
= VB
->EyePtr
->stride
;
193 input
->count
= VB
->EyePtr
->count
;
197 /* use glFogCoord() coordinates */
198 input
= VB
->FogCoordPtr
; /* source data */
199 VB
->FogCoordPtr
= &store
->fogcoord
; /* dest data */
202 if (tnl
->_DoVertexFog
) {
203 /* compute blend factors from fog coordinates */
204 compute_fog_blend_factors( ctx
, VB
->FogCoordPtr
, input
);
207 /* results = incoming fog coords (compute fog per-fragment later) */
208 VB
->FogCoordPtr
= input
;
211 VB
->AttribPtr
[_TNL_ATTRIB_FOG
] = VB
->FogCoordPtr
;
217 check_fog_stage(GLcontext
*ctx
, struct tnl_pipeline_stage
*stage
)
219 stage
->active
= ctx
->Fog
.Enabled
&& !ctx
->VertexProgram
._Enabled
;
221 if (ctx
->Fog
.FogCoordinateSource
== GL_FRAGMENT_DEPTH_EXT
)
222 stage
->inputs
= _TNL_BIT_POS
;
224 stage
->inputs
= _TNL_BIT_FOG
;
228 /* Called the first time stage->run() is invoked.
231 alloc_fog_data(GLcontext
*ctx
, struct tnl_pipeline_stage
*stage
)
233 TNLcontext
*tnl
= TNL_CONTEXT(ctx
);
234 struct fog_stage_data
*store
;
235 stage
->privatePtr
= MALLOC(sizeof(*store
));
236 store
= FOG_STAGE_DATA(stage
);
240 _mesa_vector4f_alloc( &store
->fogcoord
, 0, tnl
->vb
.Size
, 32 );
241 _mesa_vector4f_init( &store
->input
, 0, 0 );
246 /* Now run the stage.
248 stage
->run
= run_fog_stage
;
249 return stage
->run( ctx
, stage
);
254 free_fog_data(struct tnl_pipeline_stage
*stage
)
256 struct fog_stage_data
*store
= FOG_STAGE_DATA(stage
);
258 _mesa_vector4f_free( &store
->fogcoord
);
260 stage
->privatePtr
= NULL
;
265 const struct tnl_pipeline_stage _tnl_fog_coordinate_stage
=
267 "build fog coordinates", /* name */
268 _NEW_FOG
|_NEW_PROGRAM
, /* check_state */
269 _NEW_FOG
, /* run_state */
270 GL_FALSE
, /* active? */
272 _TNL_BIT_FOG
, /* outputs */
273 0, /* changed_inputs */
274 NULL
, /* private_data */
275 free_fog_data
, /* dtr */
276 check_fog_stage
, /* check */
277 alloc_fog_data
/* run -- initially set to init. */