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
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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
42struct 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
49static inline struct cull_stage *cull_stage( struct draw_stage *stage )
50{
51   return (struct cull_stage *)stage;
52}
53
54static inline boolean
55cull_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 */
66static 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 */
96static 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 */
127static 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      } else {
185         /*
186          * With zero area, this is back facing (because the spec says
187          * it's front facing if sign is positive?).
188          * Some apis apparently do not allow us to cull zero area tris
189          * here, in case of fill mode line (which is rather lame).
190          */
191         if ((PIPE_FACE_BACK & cull_stage(stage)->cull_face) == 0) {
192            stage->next->tri( stage->next, header );
193         }
194      }
195   }
196}
197
198static void cull_first_point( struct draw_stage *stage,
199                              struct prim_header *header )
200{
201   const unsigned num_written_culldistances =
202      draw_current_shader_num_written_culldistances(stage->draw);
203
204   if (num_written_culldistances) {
205      stage->point = cull_point;
206      stage->point( stage, header );
207   } else {
208      stage->point = draw_pipe_passthrough_point;
209      stage->point( stage, header );
210   }
211}
212
213static void cull_first_line( struct draw_stage *stage,
214			    struct prim_header *header )
215{
216   const unsigned num_written_culldistances =
217      draw_current_shader_num_written_culldistances(stage->draw);
218
219   if (num_written_culldistances) {
220      stage->line = cull_line;
221      stage->line( stage, header );
222   } else {
223      stage->line = draw_pipe_passthrough_line;
224      stage->line( stage, header );
225   }
226}
227
228static void cull_first_tri( struct draw_stage *stage,
229			    struct prim_header *header )
230{
231   struct cull_stage *cull = cull_stage(stage);
232
233   cull->cull_face = stage->draw->rasterizer->cull_face;
234   cull->front_ccw = stage->draw->rasterizer->front_ccw;
235
236   stage->tri = cull_tri;
237   stage->tri( stage, header );
238}
239
240
241static void cull_flush( struct draw_stage *stage, unsigned flags )
242{
243   stage->point = cull_first_point;
244   stage->line = cull_first_line;
245   stage->tri = cull_first_tri;
246   stage->next->flush( stage->next, flags );
247}
248
249
250static void cull_reset_stipple_counter( struct draw_stage *stage )
251{
252   stage->next->reset_stipple_counter( stage->next );
253}
254
255
256static void cull_destroy( struct draw_stage *stage )
257{
258   draw_free_temp_verts( stage );
259   FREE( stage );
260}
261
262
263/**
264 * Create a new polygon culling stage.
265 */
266struct draw_stage *draw_cull_stage( struct draw_context *draw )
267{
268   struct cull_stage *cull = CALLOC_STRUCT(cull_stage);
269   if (!cull)
270      goto fail;
271
272   cull->stage.draw = draw;
273   cull->stage.name = "cull";
274   cull->stage.next = NULL;
275   cull->stage.point = cull_first_point;
276   cull->stage.line = cull_first_line;
277   cull->stage.tri = cull_first_tri;
278   cull->stage.flush = cull_flush;
279   cull->stage.reset_stipple_counter = cull_reset_stipple_counter;
280   cull->stage.destroy = cull_destroy;
281
282   if (!draw_alloc_temp_verts( &cull->stage, 0 ))
283      goto fail;
284
285   return &cull->stage;
286
287fail:
288   if (cull)
289      cull->stage.destroy( &cull->stage );
290
291   return NULL;
292}
293