2 * Mesa 3-D graphics library
5 * Copyright (C) 1999-2006 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
] = EXPF(-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
= *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
= *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
= *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 (!ctx
->Fog
.Enabled
|| ctx
->VertexProgram
._Current
)
155 if (ctx
->Fog
.FogCoordinateSource
== GL_FRAGMENT_DEPTH_EXT
) {
158 /* Fog is computed from vertex or fragment Z values */
159 /* source = VB->ObjPtr or VB->EyePtr coords */
160 /* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
161 VB
->AttribPtr
[_TNL_ATTRIB_FOG
] = &store
->fogcoord
;
163 if (!ctx
->_NeedEyeCoords
) {
164 /* compute fog coords from object coords */
165 const GLfloat
*m
= ctx
->ModelviewMatrixStack
.Top
->m
;
168 /* Use this to store calculated eye z values:
170 input
= &store
->fogcoord
;
172 /* NOTE: negate plane here so we get positive fog coords! */
173 /* NOTE2: this doesn't always work (tests/fog - all frag depth fog
174 coords will be negative). */
179 /* Full eye coords weren't required, just calculate the
182 _mesa_dotprod_tab
[VB
->ObjPtr
->size
]( (GLfloat
*) input
->data
,
186 input
->count
= VB
->ObjPtr
->count
;
188 /* make sure coords are really positive
189 NOTE should avoid going through array twice */
190 coord
= input
->start
;
191 for (i
= 0; i
< input
->count
; i
++) {
192 input
->data
[i
][0] = FABSF(*coord
);
193 STRIDE_F(coord
, input
->stride
);
197 /* fog coordinates = eye Z coordinates (use ABS later) */
198 input
= &store
->fogcoord
;
200 if (VB
->EyePtr
->size
< 2)
201 _mesa_vector4f_clean_elem( VB
->EyePtr
, VB
->Count
, 2 );
203 input
->stride
= 4 * sizeof(GLfloat
);
204 input
->count
= VB
->EyePtr
->count
;
205 coord
= VB
->EyePtr
->start
;
206 for (i
= 0 ; i
< VB
->EyePtr
->count
; i
++) {
207 input
->data
[i
][0] = FABSF(coord
[2]);
208 STRIDE_F(coord
, VB
->EyePtr
->stride
);
213 /* use glFogCoord() coordinates */
214 input
= VB
->AttribPtr
[_TNL_ATTRIB_FOG
]; /* source data */
216 /* input->count may be one if glFogCoord was only called once
217 * before glBegin. But we need to compute fog for all vertices.
219 input
->count
= VB
->ObjPtr
->count
;
221 VB
->AttribPtr
[_TNL_ATTRIB_FOG
] = &store
->fogcoord
; /* dest data */
224 if (tnl
->_DoVertexFog
) {
225 /* compute blend factors from fog coordinates */
226 compute_fog_blend_factors( ctx
, VB
->AttribPtr
[_TNL_ATTRIB_FOG
], input
);
229 /* results = incoming fog coords (compute fog per-fragment later) */
230 VB
->AttribPtr
[_TNL_ATTRIB_FOG
] = input
;
233 VB
->FogCoordPtr
= VB
->AttribPtr
[_TNL_ATTRIB_FOG
];
239 /* Called the first time stage->run() is invoked.
242 alloc_fog_data(GLcontext
*ctx
, struct tnl_pipeline_stage
*stage
)
244 TNLcontext
*tnl
= TNL_CONTEXT(ctx
);
245 struct fog_stage_data
*store
;
246 stage
->privatePtr
= MALLOC(sizeof(*store
));
247 store
= FOG_STAGE_DATA(stage
);
251 _mesa_vector4f_alloc( &store
->fogcoord
, 0, tnl
->vb
.Size
, 32 );
252 _mesa_vector4f_init( &store
->input
, 0, NULL
);
262 free_fog_data(struct tnl_pipeline_stage
*stage
)
264 struct fog_stage_data
*store
= FOG_STAGE_DATA(stage
);
266 _mesa_vector4f_free( &store
->fogcoord
);
268 stage
->privatePtr
= NULL
;
273 const struct tnl_pipeline_stage _tnl_fog_coordinate_stage
=
275 "build fog coordinates", /* name */
276 NULL
, /* private_data */
277 alloc_fog_data
, /* dtr */
278 free_fog_data
, /* dtr */
280 run_fog_stage
/* run -- initially set to init. */