1 /**************************************************************************
3 * Copyright 2007 VMware, Inc.
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
26 **************************************************************************/
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 * Triangles can be culled using regular face cull.
57 static void cull_tri( struct draw_stage
*stage
,
58 struct prim_header
*header
)
60 /* Do the regular face culling */
62 const unsigned pos
= draw_current_shader_position_output(stage
->draw
);
64 const float *v0
= header
->v
[0]->data
[pos
];
65 const float *v1
= header
->v
[1]->data
[pos
];
66 const float *v2
= header
->v
[2]->data
[pos
];
68 /* edge vectors: e = v0 - v2, f = v1 - v2 */
69 const float ex
= v0
[0] - v2
[0];
70 const float ey
= v0
[1] - v2
[1];
71 const float fx
= v1
[0] - v2
[0];
72 const float fy
= v1
[1] - v2
[1];
75 /* det = cross(e,f).z */
76 header
->det
= ex
* fy
- ey
* fx
;
78 if (header
->det
!= 0) {
79 /* if det < 0 then Z points toward the camera and the triangle is
80 * counter-clockwise winding.
82 unsigned ccw
= (header
->det
< 0);
83 unsigned face
= ((ccw
== cull_stage(stage
)->front_ccw
) ?
87 if ((face
& cull_stage(stage
)->cull_face
) == 0) {
88 /* triangle is not culled, pass to next stage */
89 stage
->next
->tri( stage
->next
, header
);
93 * With zero area, this is back facing (because the spec says
94 * it's front facing if sign is positive?).
95 * Some apis apparently do not allow us to cull zero area tris
96 * here, in case of fill mode line (which is rather lame).
98 if ((PIPE_FACE_BACK
& cull_stage(stage
)->cull_face
) == 0) {
99 stage
->next
->tri( stage
->next
, header
);
105 static void cull_first_tri( struct draw_stage
*stage
,
106 struct prim_header
*header
)
108 struct cull_stage
*cull
= cull_stage(stage
);
110 cull
->cull_face
= stage
->draw
->rasterizer
->cull_face
;
111 cull
->front_ccw
= stage
->draw
->rasterizer
->front_ccw
;
113 stage
->tri
= cull_tri
;
114 stage
->tri( stage
, header
);
118 static void cull_flush( struct draw_stage
*stage
, unsigned flags
)
120 stage
->tri
= cull_first_tri
;
121 stage
->next
->flush( stage
->next
, flags
);
125 static void cull_reset_stipple_counter( struct draw_stage
*stage
)
127 stage
->next
->reset_stipple_counter( stage
->next
);
131 static void cull_destroy( struct draw_stage
*stage
)
133 draw_free_temp_verts( stage
);
139 * Create a new polygon culling stage.
141 struct draw_stage
*draw_cull_stage( struct draw_context
*draw
)
143 struct cull_stage
*cull
= CALLOC_STRUCT(cull_stage
);
147 cull
->stage
.draw
= draw
;
148 cull
->stage
.name
= "cull";
149 cull
->stage
.next
= NULL
;
150 cull
->stage
.point
= draw_pipe_passthrough_point
;
151 cull
->stage
.line
= draw_pipe_passthrough_line
;
152 cull
->stage
.tri
= cull_first_tri
;
153 cull
->stage
.flush
= cull_flush
;
154 cull
->stage
.reset_stipple_counter
= cull_reset_stipple_counter
;
155 cull
->stage
.destroy
= cull_destroy
;
157 if (!draw_alloc_temp_verts( &cull
->stage
, 0 ))
164 cull
->stage
.destroy( &cull
->stage
);