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 "util/u_math.h"
  36 #include "util/u_memory.h"
  37 #include "draw_pipe.h"
  38
  39
  40
  41 struct offset_stage {
  42    struct draw_stage stage;
  43
  44    float scale;
  45    float units;
  46 };
  47
  48
  49
  50 static INLINE struct offset_stage *offset_stage( struct draw_stage *stage )
  51 {
  52    return (struct offset_stage *) stage;
  53 }
  54
  55
  56
  57
  58
  59 /**
  60  * Offset tri Z.  Some hardware can handle this, but not usually when
  61  * doing unfilled rendering.
  62  */
  63 static void do_offset_tri( struct draw_stage *stage,
  64                            struct prim_header *header )
  65 {
  66    const unsigned pos = draw_current_shader_position_output(stage->draw);
  67    struct offset_stage *offset = offset_stage(stage);
  68    float inv_det = 1.0f / header->det;
  69
  70    /* Window coords:
  71     */
  72    float *v0 = header->v[0]->data[pos];
  73    float *v1 = header->v[1]->data[pos];
  74    float *v2 = header->v[2]->data[pos];
  75
  76    /* edge vectors e = v0 - v2, f = v1 - v2 */
  77    float ex = v0[0] - v2[0];
  78    float ey = v0[1] - v2[1];
  79    float ez = v0[2] - v2[2];
  80    float fx = v1[0] - v2[0];
  81    float fy = v1[1] - v2[1];
  82    float fz = v1[2] - v2[2];
  83
  84    /* (a,b) = cross(e,f).xy */
  85    float a = ey*fz - ez*fy;
  86    float b = ez*fx - ex*fz;
  87
  88    float dzdx = fabsf(a * inv_det);
  89    float dzdy = fabsf(b * inv_det);
  90
  91    float zoffset = offset->units + MAX2(dzdx, dzdy) * offset->scale;
  92
  93    /*
  94     * Note: we're applying the offset and clamping per-vertex.
  95     * Ideally, the offset is applied per-fragment prior to fragment shading.
  96     */
  97    v0[2] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);
  98    v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);
  99    v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);
 100
 101    stage->next->tri( stage->next, header );
 102 }
 103
 104
 105 static void offset_tri( struct draw_stage *stage,
 106                         struct prim_header *header )
 107 {
 108    struct prim_header tmp;
 109
 110    tmp.det = header->det;
 111    tmp.flags = header->flags;
 112    tmp.pad = header->pad;
 113    tmp.v[0] = dup_vert(stage, header->v[0], 0);
 114    tmp.v[1] = dup_vert(stage, header->v[1], 1);
 115    tmp.v[2] = dup_vert(stage, header->v[2], 2);
 116
 117    do_offset_tri( stage, &tmp );
 118 }
 119
 120
 121 static void offset_first_tri( struct draw_stage *stage,
 122                               struct prim_header *header )
 123 {
 124    struct offset_stage *offset = offset_stage(stage);
 125
 126    offset->units = (float) (stage->draw->rasterizer->offset_units * stage->draw->mrd);
 127    offset->scale = stage->draw->rasterizer->offset_scale;
 128
 129    stage->tri = offset_tri;
 130    stage->tri( stage, header );
 131 }
 132
 133
 134
 135
 136 static void offset_flush( struct draw_stage *stage,
 137                           unsigned flags )
 138 {
 139    stage->tri = offset_first_tri;
 140    stage->next->flush( stage->next, flags );
 141 }
 142
 143
 144 static void offset_reset_stipple_counter( struct draw_stage *stage )
 145 {
 146    stage->next->reset_stipple_counter( stage->next );
 147 }
 148
 149
 150 static void offset_destroy( struct draw_stage *stage )
 151 {
 152    draw_free_temp_verts( stage );
 153    FREE( stage );
 154 }
 155
 156
 157 /**
 158  * Create polygon offset drawing stage.
 159  */
 160 struct draw_stage *draw_offset_stage( struct draw_context *draw )
 161 {
 162    struct offset_stage *offset = CALLOC_STRUCT(offset_stage);
 163    if (offset == NULL)
 164       goto fail;
 165
 166    draw_alloc_temp_verts( &offset->stage, 3 );
 167
 168    offset->stage.draw = draw;
 169    offset->stage.name = "offset";
 170    offset->stage.next = NULL;
 171    offset->stage.point = draw_pipe_passthrough_point;
 172    offset->stage.line = draw_pipe_passthrough_line;
 173    offset->stage.tri = offset_first_tri;
 174    offset->stage.flush = offset_flush;
 175    offset->stage.reset_stipple_counter = offset_reset_stipple_counter;
 176    offset->stage.destroy = offset_destroy;
 177
 178    return &offset->stage;
 179
 180  fail:
 181    if (offset)
 182       offset->stage.destroy( &offset->stage );
 183
 184    return NULL;
 185 }