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
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.
25 *
26 **************************************************************************/
27
28/**
29 * \brief  polygon offset state
30 *
31 * \author  Keith Whitwell <keithw@vmware.com>
32 * \author  Brian Paul
33 */
34
35#include "util/format/u_format.h"
36#include "util/u_math.h"
37#include "util/u_memory.h"
38#include "draw_pipe.h"
39
40
41
42struct offset_stage {
43   struct draw_stage stage;
44
45   float scale;
46   float units;
47   float clamp;
48};
49
50
51
52static inline struct offset_stage *offset_stage( struct draw_stage *stage )
53{
54   return (struct offset_stage *) stage;
55}
56
57
58
59
60
61/**
62 * Offset tri Z.  Some hardware can handle this, but not usually when
63 * doing unfilled rendering.
64 */
65static void do_offset_tri( struct draw_stage *stage,
66			   struct prim_header *header )
67{
68   const unsigned pos = draw_current_shader_position_output(stage->draw);
69   struct offset_stage *offset = offset_stage(stage);
70   float inv_det = 1.0f / header->det;
71
72   /* Window coords:
73    */
74   float *v0 = header->v[0]->data[pos];
75   float *v1 = header->v[1]->data[pos];
76   float *v2 = header->v[2]->data[pos];
77
78   /* edge vectors e = v0 - v2, f = v1 - v2 */
79   float ex = v0[0] - v2[0];
80   float ey = v0[1] - v2[1];
81   float ez = v0[2] - v2[2];
82   float fx = v1[0] - v2[0];
83   float fy = v1[1] - v2[1];
84   float fz = v1[2] - v2[2];
85
86   /* (a,b) = cross(e,f).xy */
87   float a = ey*fz - ez*fy;
88   float b = ez*fx - ex*fz;
89
90   float dzdx = fabsf(a * inv_det);
91   float dzdy = fabsf(b * inv_det);
92
93   float zoffset, mult;
94
95   mult = MAX2(dzdx, dzdy) * offset->scale;
96
97   if (stage->draw->floating_point_depth) {
98      float bias;
99      union fi maxz;
100      maxz.f = MAX3(fabs(v0[2]), fabs(v1[2]), fabs(v2[2]));
101      /* just do the math directly on shifted number */
102      maxz.ui &= 0xff << 23;
103      maxz.i -= 23 << 23;
104      /* Clamping to zero means mrd will be zero for very small numbers,
105       * but specs do not indicate this should be prevented by clamping
106       * mrd to smallest normal number instead. */
107      maxz.i = MAX2(maxz.i, 0);
108
109      bias = offset->units * maxz.f;
110      zoffset = bias + mult;
111   } else {
112      zoffset = offset->units + mult;
113   }
114
115   if (offset->clamp)
116      zoffset = (offset->clamp < 0.0f) ? MAX2(zoffset, offset->clamp) :
117                                         MIN2(zoffset, offset->clamp);
118
119   /*
120    * Note: we're applying the offset and clamping per-vertex.
121    * Ideally, the offset is applied per-fragment prior to fragment shading.
122    */
123   v0[2] = SATURATE(v0[2] + zoffset);
124   v1[2] = SATURATE(v1[2] + zoffset);
125   v2[2] = SATURATE(v2[2] + zoffset);
126
127   stage->next->tri( stage->next, header );
128}
129
130
131static void offset_tri( struct draw_stage *stage,
132			struct prim_header *header )
133{
134   struct prim_header tmp;
135
136   tmp.det = header->det;
137   tmp.flags = header->flags;
138   tmp.pad = header->pad;
139   tmp.v[0] = dup_vert(stage, header->v[0], 0);
140   tmp.v[1] = dup_vert(stage, header->v[1], 1);
141   tmp.v[2] = dup_vert(stage, header->v[2], 2);
142
143   do_offset_tri( stage, &tmp );
144}
145
146
147static void offset_first_tri( struct draw_stage *stage,
148			      struct prim_header *header )
149{
150   struct offset_stage *offset = offset_stage(stage);
151   const struct pipe_rasterizer_state *rast = stage->draw->rasterizer;
152   unsigned fill_mode = rast->fill_front;
153   boolean do_offset;
154
155   if (rast->fill_back != rast->fill_front) {
156      /* Need to check for back-facing triangle */
157      boolean ccw = header->det < 0.0f;
158      if (ccw != rast->front_ccw)
159         fill_mode = rast->fill_back;
160   }
161
162   /* Now determine if we need to do offsetting for the point/line/fill mode */
163   switch (fill_mode) {
164   case PIPE_POLYGON_MODE_FILL:
165      do_offset = rast->offset_tri;
166      break;
167   case PIPE_POLYGON_MODE_LINE:
168      do_offset = rast->offset_line;
169      break;
170   case PIPE_POLYGON_MODE_POINT:
171      do_offset = rast->offset_point;
172      break;
173   default:
174      assert(!"invalid fill_mode in offset_first_tri()");
175      do_offset = rast->offset_tri;
176   }
177
178   if (do_offset) {
179      offset->scale = rast->offset_scale;
180      offset->clamp = rast->offset_clamp;
181
182      /*
183       * If depth is floating point, depth bias is calculated with respect
184       * to the primitive's maximum Z value. Retain the original depth bias
185       * value until that stage.
186       */
187      if (stage->draw->floating_point_depth) {
188         offset->units = (float) rast->offset_units;
189      } else {
190         offset->units = (float) (rast->offset_units * stage->draw->mrd * 2);
191      }
192   }
193   else {
194      offset->scale = 0.0f;
195      offset->clamp = 0.0f;
196      offset->units = 0.0f;
197   }
198
199
200   stage->tri = offset_tri;
201   stage->tri( stage, header );
202}
203
204
205
206
207static void offset_flush( struct draw_stage *stage,
208			  unsigned flags )
209{
210   stage->tri = offset_first_tri;
211   stage->next->flush( stage->next, flags );
212}
213
214
215static void offset_reset_stipple_counter( struct draw_stage *stage )
216{
217   stage->next->reset_stipple_counter( stage->next );
218}
219
220
221static void offset_destroy( struct draw_stage *stage )
222{
223   draw_free_temp_verts( stage );
224   FREE( stage );
225}
226
227
228/**
229 * Create polygon offset drawing stage.
230 */
231struct draw_stage *draw_offset_stage( struct draw_context *draw )
232{
233   struct offset_stage *offset = CALLOC_STRUCT(offset_stage);
234   if (!offset)
235      goto fail;
236
237   offset->stage.draw = draw;
238   offset->stage.name = "offset";
239   offset->stage.next = NULL;
240   offset->stage.point = draw_pipe_passthrough_point;
241   offset->stage.line = draw_pipe_passthrough_line;
242   offset->stage.tri = offset_first_tri;
243   offset->stage.flush = offset_flush;
244   offset->stage.reset_stipple_counter = offset_reset_stipple_counter;
245   offset->stage.destroy = offset_destroy;
246
247   if (!draw_alloc_temp_verts( &offset->stage, 3 ))
248      goto fail;
249
250   return &offset->stage;
251
252fail:
253   if (offset)
254      offset->stage.destroy( &offset->stage );
255
256   return NULL;
257}
258