src/gallium/auxiliary/draw/draw_pipe_offset.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   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 TUNGSTEN GRAPHICS 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 <keith@tungstengraphics.com>
  32  * \author  Brian Paul
  33  */
  34
  35 #include "pipe/p_util.h"
  36 #include "draw_pipe.h"
  37
  38
  39
  40 struct offset_stage {
  41    struct draw_stage stage;
  42
  43    float scale;
  44    float units;
  45 };
  46
  47
  48
  49 static INLINE struct offset_stage *offset_stage( struct draw_stage *stage )
  50 {
  51    return (struct offset_stage *) stage;
  52 }
  53
  54
  55
  56
  57
  58 /**
  59  * Offset tri Z.  Some hardware can handle this, but not usually when
  60  * doing unfilled rendering.
  61  */
  62 static void do_offset_tri( struct draw_stage *stage,
  63                            struct prim_header *header )
  64 {
  65    struct offset_stage *offset = offset_stage(stage);
  66    float inv_det = 1.0f / header->det;
  67
  68    /* Window coords:
  69     */
  70    float *v0 = header->v[0]->data[0];
  71    float *v1 = header->v[1]->data[0];
  72    float *v2 = header->v[2]->data[0];
  73
  74    /* edge vectors e = v0 - v2, f = v1 - v2 */
  75    float ex = v0[0] - v2[0];
  76    float ey = v0[1] - v2[1];
  77    float ez = v0[2] - v2[2];
  78    float fx = v1[0] - v2[0];
  79    float fy = v1[1] - v2[1];
  80    float fz = v1[2] - v2[2];
  81
  82    /* (a,b) = cross(e,f).xy */
  83    float a = ey*fz - ez*fy;
  84    float b = ez*fx - ex*fz;
  85
  86    float dzdx = FABSF(a * inv_det);
  87    float dzdy = FABSF(b * inv_det);
  88
  89    float zoffset = offset->units + MAX2(dzdx, dzdy) * offset->scale;
  90
  91    /*
  92     * Note: we're applying the offset and clamping per-vertex.
  93     * Ideally, the offset is applied per-fragment prior to fragment shading.
  94     */
  95    v0[2] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);
  96    v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);
  97    v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);
  98
  99    stage->next->tri( stage->next, header );
 100 }
 101
 102
 103 static void offset_tri( struct draw_stage *stage,
 104                         struct prim_header *header )
 105 {
 106    struct prim_header tmp;
 107
 108    tmp.det = header->det;
 109    tmp.flags = header->flags;
 110    tmp.pad = header->pad;
 111    tmp.v[0] = dup_vert(stage, header->v[0], 0);
 112    tmp.v[1] = dup_vert(stage, header->v[1], 1);
 113    tmp.v[2] = dup_vert(stage, header->v[2], 2);
 114
 115    do_offset_tri( stage, &tmp );
 116 }
 117
 118
 119 static void offset_first_tri( struct draw_stage *stage,
 120                               struct prim_header *header )
 121 {
 122    struct offset_stage *offset = offset_stage(stage);
 123    float mrd = 1.0f / 65535.0f; /* XXX this depends on depthbuffer bits! */
 124
 125    offset->units = stage->draw->rasterizer->offset_units * mrd;
 126    offset->scale = stage->draw->rasterizer->offset_scale;
 127
 128    stage->tri = offset_tri;
 129    stage->tri( stage, header );
 130 }
 131
 132
 133
 134
 135 static void offset_flush( struct draw_stage *stage,
 136                           unsigned flags )
 137 {
 138    stage->tri = offset_first_tri;
 139    stage->next->flush( stage->next, flags );
 140 }
 141
 142
 143 static void offset_reset_stipple_counter( struct draw_stage *stage )
 144 {
 145    stage->next->reset_stipple_counter( stage->next );
 146 }
 147
 148
 149 static void offset_destroy( struct draw_stage *stage )
 150 {
 151    draw_free_temp_verts( stage );
 152    FREE( stage );
 153 }
 154
 155
 156 /**
 157  * Create polygon offset drawing stage.
 158  */
 159 struct draw_stage *draw_offset_stage( struct draw_context *draw )
 160 {
 161    struct offset_stage *offset = CALLOC_STRUCT(offset_stage);
 162    if (offset == NULL)
 163       goto fail;
 164
 165    draw_alloc_temp_verts( &offset->stage, 3 );
 166
 167    offset->stage.draw = draw;
 168    offset->stage.next = NULL;
 169    offset->stage.point = draw_pipe_passthrough_point;
 170    offset->stage.line = draw_pipe_passthrough_line;
 171    offset->stage.tri = offset_first_tri;
 172    offset->stage.flush = offset_flush;
 173    offset->stage.reset_stipple_counter = offset_reset_stipple_counter;
 174    offset->stage.destroy = offset_destroy;
 175
 176    return &offset->stage;
 177
 178  fail:
 179    if (offset)
 180       offset->stage.destroy( &offset->stage );
 181
 182    return NULL;
 183 }