1 /**************************************************************************
2 *
3 * Copyright 2007 VMware, Inc.
4 * All Rights Reserved.
5 *
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:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
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
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23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 **************************************************************************/
27
28 /**
29 * \brief Drawing stage for polygon culling
30 */
31
32 /* Authors: Keith Whitwell <keithw@vmware.com>
33 */
34
35
36 #include "util/u_math.h"
37 #include "util/u_memory.h"
38 #include "pipe/p_defines.h"
39 #include "draw_pipe.h"
40
41
42 struct cull_stage {
43 struct draw_stage stage;
44 unsigned cull_face; /**< which face(s) to cull (one of PIPE_FACE_x) */
45 unsigned front_ccw;
46 };
47
48
cull_stage(struct draw_stage * stage)49 static inline struct cull_stage *cull_stage( struct draw_stage *stage )
50 {
51 return (struct cull_stage *)stage;
52 }
53
54 static inline boolean
cull_distance_is_out(float dist)55 cull_distance_is_out(float dist)
56 {
57 return (dist < 0.0f) || util_is_inf_or_nan(dist);
58 }
59
60 /*
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)
65 */
cull_point(struct draw_stage * stage,struct prim_header * header)66 static void cull_point( struct draw_stage *stage,
67 struct prim_header *header )
68 {
69 const unsigned num_written_culldistances =
70 draw_current_shader_num_written_culldistances(stage->draw);
71 const unsigned num_written_clipdistances =
72 draw_current_shader_num_written_clipdistances(stage->draw);
73 unsigned i;
74
75 debug_assert(num_written_culldistances);
76
77 for (i = 0; i < num_written_culldistances; ++i) {
78 unsigned cull_idx = (num_written_clipdistances + i) / 4;
79 unsigned out_idx =
80 draw_current_shader_ccdistance_output(stage->draw, cull_idx);
81 unsigned idx = (num_written_clipdistances + i) % 4;
82 float cull1 = header->v[0]->data[out_idx][idx];
83 boolean vert1_out = cull_distance_is_out(cull1);
84 if (vert1_out)
85 return;
86 }
87 stage->next->point( stage->next, header );
88 }
89
90 /*
91 * If the shader writes the culldistance then we can
92 * perform distance based culling. Distance based
93 * culling doesn't require a face and can be performed
94 * on primitives without faces (e.g. points and lines)
95 */
cull_line(struct draw_stage * stage,struct prim_header * header)96 static void cull_line( struct draw_stage *stage,
97 struct prim_header *header )
98 {
99 const unsigned num_written_culldistances =
100 draw_current_shader_num_written_culldistances(stage->draw);
101 const unsigned num_written_clipdistances =
102 draw_current_shader_num_written_clipdistances(stage->draw);
103 unsigned i;
104
105 debug_assert(num_written_culldistances);
106
107 for (i = 0; i < num_written_culldistances; ++i) {
108 unsigned cull_idx = (num_written_clipdistances + i) / 4;
109 unsigned out_idx =
110 draw_current_shader_ccdistance_output(stage->draw, cull_idx);
111 unsigned idx = (num_written_clipdistances + i) % 4;
112 float cull1 = header->v[0]->data[out_idx][idx];
113 float cull2 = header->v[1]->data[out_idx][idx];
114 boolean vert1_out = cull_distance_is_out(cull1);
115 boolean vert2_out = cull_distance_is_out(cull2);
116 if (vert1_out && vert2_out)
117 return;
118 }
119 stage->next->line( stage->next, header );
120 }
121
122 /*
123 * Triangles can be culled either using the cull distance
124 * shader outputs or the regular face culling. If required
125 * this function performs both, starting with distance culling.
126 */
cull_tri(struct draw_stage * stage,struct prim_header * header)127 static void cull_tri( struct draw_stage *stage,
128 struct prim_header *header )
129 {
130 const unsigned num_written_culldistances =
131 draw_current_shader_num_written_culldistances(stage->draw);
132 const unsigned num_written_clipdistances =
133 draw_current_shader_num_written_clipdistances(stage->draw);
134 /* Do the distance culling */
135 if (num_written_culldistances) {
136 unsigned i;
137 for (i = 0; i < num_written_culldistances; ++i) {
138 unsigned cull_idx = (num_written_clipdistances + i) / 4;
139 unsigned out_idx =
140 draw_current_shader_ccdistance_output(stage->draw, cull_idx);
141 unsigned idx = (num_written_clipdistances + i) % 4;
142 float cull1 = header->v[0]->data[out_idx][idx];
143 float cull2 = header->v[1]->data[out_idx][idx];
144 float cull3 = header->v[2]->data[out_idx][idx];
145 boolean vert1_out = cull_distance_is_out(cull1);
146 boolean vert2_out = cull_distance_is_out(cull2);
147 boolean vert3_out = cull_distance_is_out(cull3);
148 if (vert1_out && vert2_out && vert3_out)
149 return;
150 }
151 }
152
153 /* Do the regular face culling */
154 {
155 const unsigned pos = draw_current_shader_position_output(stage->draw);
156 /* Window coords: */
157 const float *v0 = header->v[0]->data[pos];
158 const float *v1 = header->v[1]->data[pos];
159 const float *v2 = header->v[2]->data[pos];
160
161 /* edge vectors: e = v0 - v2, f = v1 - v2 */
162 const float ex = v0[0] - v2[0];
163 const float ey = v0[1] - v2[1];
164 const float fx = v1[0] - v2[0];
165 const float fy = v1[1] - v2[1];
166
167
168 /* det = cross(e,f).z */
169 header->det = ex * fy - ey * fx;
170
171 if (header->det != 0) {
172 /* if det < 0 then Z points toward the camera and the triangle is
173 * counter-clockwise winding.
174 */
175 unsigned ccw = (header->det < 0);
176 unsigned face = ((ccw == cull_stage(stage)->front_ccw) ?
177 PIPE_FACE_FRONT :
178 PIPE_FACE_BACK);
179
180 if ((face & cull_stage(stage)->cull_face) == 0) {
181 /* triangle is not culled, pass to next stage */
182 stage->next->tri( stage->next, header );
183 }
184 }
185 }
186 }
187
cull_first_point(struct draw_stage * stage,struct prim_header * header)188 static void cull_first_point( struct draw_stage *stage,
189 struct prim_header *header )
190 {
191 const unsigned num_written_culldistances =
192 draw_current_shader_num_written_culldistances(stage->draw);
193
194 if (num_written_culldistances) {
195 stage->point = cull_point;
196 stage->point( stage, header );
197 } else {
198 stage->point = draw_pipe_passthrough_point;
199 stage->point( stage, header );
200 }
201 }
202
cull_first_line(struct draw_stage * stage,struct prim_header * header)203 static void cull_first_line( struct draw_stage *stage,
204 struct prim_header *header )
205 {
206 const unsigned num_written_culldistances =
207 draw_current_shader_num_written_culldistances(stage->draw);
208
209 if (num_written_culldistances) {
210 stage->line = cull_line;
211 stage->line( stage, header );
212 } else {
213 stage->line = draw_pipe_passthrough_line;
214 stage->line( stage, header );
215 }
216 }
217
cull_first_tri(struct draw_stage * stage,struct prim_header * header)218 static void cull_first_tri( struct draw_stage *stage,
219 struct prim_header *header )
220 {
221 struct cull_stage *cull = cull_stage(stage);
222
223 cull->cull_face = stage->draw->rasterizer->cull_face;
224 cull->front_ccw = stage->draw->rasterizer->front_ccw;
225
226 stage->tri = cull_tri;
227 stage->tri( stage, header );
228 }
229
230
cull_flush(struct draw_stage * stage,unsigned flags)231 static void cull_flush( struct draw_stage *stage, unsigned flags )
232 {
233 stage->point = cull_first_point;
234 stage->line = cull_first_line;
235 stage->tri = cull_first_tri;
236 stage->next->flush( stage->next, flags );
237 }
238
239
cull_reset_stipple_counter(struct draw_stage * stage)240 static void cull_reset_stipple_counter( struct draw_stage *stage )
241 {
242 stage->next->reset_stipple_counter( stage->next );
243 }
244
245
cull_destroy(struct draw_stage * stage)246 static void cull_destroy( struct draw_stage *stage )
247 {
248 draw_free_temp_verts( stage );
249 FREE( stage );
250 }
251
252
253 /**
254 * Create a new polygon culling stage.
255 */
draw_cull_stage(struct draw_context * draw)256 struct draw_stage *draw_cull_stage( struct draw_context *draw )
257 {
258 struct cull_stage *cull = CALLOC_STRUCT(cull_stage);
259 if (!cull)
260 goto fail;
261
262 cull->stage.draw = draw;
263 cull->stage.name = "cull";
264 cull->stage.next = NULL;
265 cull->stage.point = cull_first_point;
266 cull->stage.line = cull_first_line;
267 cull->stage.tri = cull_first_tri;
268 cull->stage.flush = cull_flush;
269 cull->stage.reset_stipple_counter = cull_reset_stipple_counter;
270 cull->stage.destroy = cull_destroy;
271
272 if (!draw_alloc_temp_verts( &cull->stage, 0 ))
273 goto fail;
274
275 return &cull->stage;
276
277 fail:
278 if (cull)
279 cull->stage.destroy( &cull->stage );
280
281 return NULL;
282 }
283