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29 * \brief Drawing stage for polygon culling
32 /* Authors: Keith Whitwell <keithw@vmware.com>
36 #include "util/u_math.h"
37 #include "util/u_memory.h"
38 #include "pipe/p_defines.h"
39 #include "draw_pipe.h"
43 struct draw_stage stage
;
44 unsigned cull_face
; /**< which face(s) to cull (one of PIPE_FACE_x) */
49 static inline struct cull_stage
*cull_stage( struct draw_stage
*stage
)
51 return (struct cull_stage
*)stage
;
55 cull_distance_is_out(float dist
)
57 return (dist
< 0.0f
) || util_is_inf_or_nan(dist
);
61 * If the shader writes the culldistance then we can
62 * perform distance based culling. Distance based
63 * culling doesn't require a face and can be performed
64 * on primitives without faces (e.g. points and lines)
66 static void cull_point( struct draw_stage
*stage
,
67 struct prim_header
*header
)
69 const unsigned num_written_culldistances
=
70 draw_current_shader_num_written_culldistances(stage
->draw
);
73 debug_assert(num_written_culldistances
);
75 for (i
= 0; i
< num_written_culldistances
; ++i
) {
76 unsigned cull_idx
= i
/ 4;
78 draw_current_shader_culldistance_output(stage
->draw
, cull_idx
);
80 float cull1
= header
->v
[0]->data
[out_idx
][idx
];
81 boolean vert1_out
= cull_distance_is_out(cull1
);
85 stage
->next
->point( stage
->next
, header
);
89 * If the shader writes the culldistance then we can
90 * perform distance based culling. Distance based
91 * culling doesn't require a face and can be performed
92 * on primitives without faces (e.g. points and lines)
94 static void cull_line( struct draw_stage
*stage
,
95 struct prim_header
*header
)
97 const unsigned num_written_culldistances
=
98 draw_current_shader_num_written_culldistances(stage
->draw
);
101 debug_assert(num_written_culldistances
);
103 for (i
= 0; i
< num_written_culldistances
; ++i
) {
104 unsigned cull_idx
= i
/ 4;
106 draw_current_shader_culldistance_output(stage
->draw
, cull_idx
);
107 unsigned idx
= i
% 4;
108 float cull1
= header
->v
[0]->data
[out_idx
][idx
];
109 float cull2
= header
->v
[1]->data
[out_idx
][idx
];
110 boolean vert1_out
= cull_distance_is_out(cull1
);
111 boolean vert2_out
= cull_distance_is_out(cull2
);
112 if (vert1_out
&& vert2_out
)
115 stage
->next
->line( stage
->next
, header
);
119 * Triangles can be culled either using the cull distance
120 * shader outputs or the regular face culling. If required
121 * this function performs both, starting with distance culling.
123 static void cull_tri( struct draw_stage
*stage
,
124 struct prim_header
*header
)
126 const unsigned num_written_culldistances
=
127 draw_current_shader_num_written_culldistances(stage
->draw
);
129 /* Do the distance culling */
130 if (num_written_culldistances
) {
132 for (i
= 0; i
< num_written_culldistances
; ++i
) {
133 unsigned cull_idx
= i
/ 4;
135 draw_current_shader_culldistance_output(stage
->draw
, cull_idx
);
136 unsigned idx
= i
% 4;
137 float cull1
= header
->v
[0]->data
[out_idx
][idx
];
138 float cull2
= header
->v
[1]->data
[out_idx
][idx
];
139 float cull3
= header
->v
[2]->data
[out_idx
][idx
];
140 boolean vert1_out
= cull_distance_is_out(cull1
);
141 boolean vert2_out
= cull_distance_is_out(cull2
);
142 boolean vert3_out
= cull_distance_is_out(cull3
);
143 if (vert1_out
&& vert2_out
&& vert3_out
)
148 /* Do the regular face culling */
150 const unsigned pos
= draw_current_shader_position_output(stage
->draw
);
152 const float *v0
= header
->v
[0]->data
[pos
];
153 const float *v1
= header
->v
[1]->data
[pos
];
154 const float *v2
= header
->v
[2]->data
[pos
];
156 /* edge vectors: e = v0 - v2, f = v1 - v2 */
157 const float ex
= v0
[0] - v2
[0];
158 const float ey
= v0
[1] - v2
[1];
159 const float fx
= v1
[0] - v2
[0];
160 const float fy
= v1
[1] - v2
[1];
163 /* det = cross(e,f).z */
164 header
->det
= ex
* fy
- ey
* fx
;
166 if (header
->det
!= 0) {
167 /* if det < 0 then Z points toward the camera and the triangle is
168 * counter-clockwise winding.
170 unsigned ccw
= (header
->det
< 0);
171 unsigned face
= ((ccw
== cull_stage(stage
)->front_ccw
) ?
175 if ((face
& cull_stage(stage
)->cull_face
) == 0) {
176 /* triangle is not culled, pass to next stage */
177 stage
->next
->tri( stage
->next
, header
);
183 static void cull_first_point( struct draw_stage
*stage
,
184 struct prim_header
*header
)
186 const unsigned num_written_culldistances
=
187 draw_current_shader_num_written_culldistances(stage
->draw
);
189 if (num_written_culldistances
) {
190 stage
->point
= cull_point
;
191 stage
->point( stage
, header
);
193 stage
->point
= draw_pipe_passthrough_point
;
194 stage
->point( stage
, header
);
198 static void cull_first_line( struct draw_stage
*stage
,
199 struct prim_header
*header
)
201 const unsigned num_written_culldistances
=
202 draw_current_shader_num_written_culldistances(stage
->draw
);
204 if (num_written_culldistances
) {
205 stage
->line
= cull_line
;
206 stage
->line( stage
, header
);
208 stage
->line
= draw_pipe_passthrough_line
;
209 stage
->line( stage
, header
);
213 static void cull_first_tri( struct draw_stage
*stage
,
214 struct prim_header
*header
)
216 struct cull_stage
*cull
= cull_stage(stage
);
218 cull
->cull_face
= stage
->draw
->rasterizer
->cull_face
;
219 cull
->front_ccw
= stage
->draw
->rasterizer
->front_ccw
;
221 stage
->tri
= cull_tri
;
222 stage
->tri( stage
, header
);
226 static void cull_flush( struct draw_stage
*stage
, unsigned flags
)
228 stage
->point
= cull_first_point
;
229 stage
->line
= cull_first_line
;
230 stage
->tri
= cull_first_tri
;
231 stage
->next
->flush( stage
->next
, flags
);
235 static void cull_reset_stipple_counter( struct draw_stage
*stage
)
237 stage
->next
->reset_stipple_counter( stage
->next
);
241 static void cull_destroy( struct draw_stage
*stage
)
243 draw_free_temp_verts( stage
);
249 * Create a new polygon culling stage.
251 struct draw_stage
*draw_cull_stage( struct draw_context
*draw
)
253 struct cull_stage
*cull
= CALLOC_STRUCT(cull_stage
);
257 cull
->stage
.draw
= draw
;
258 cull
->stage
.name
= "cull";
259 cull
->stage
.next
= NULL
;
260 cull
->stage
.point
= cull_first_point
;
261 cull
->stage
.line
= cull_first_line
;
262 cull
->stage
.tri
= cull_first_tri
;
263 cull
->stage
.flush
= cull_flush
;
264 cull
->stage
.reset_stipple_counter
= cull_reset_stipple_counter
;
265 cull
->stage
.destroy
= cull_destroy
;
267 if (!draw_alloc_temp_verts( &cull
->stage
, 0 ))
274 cull
->stage
.destroy( &cull
->stage
);