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,
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  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    float clamp;
  47 };
  48
  49
  50
  51 static INLINE struct offset_stage *offset_stage( struct draw_stage *stage )
  52 {
  53    return (struct offset_stage *) stage;
  54 }
  55
  56
  57
  58
  59
  60 /**
  61  * Offset tri Z.  Some hardware can handle this, but not usually when
  62  * doing unfilled rendering.
  63  */
  64 static void do_offset_tri( struct draw_stage *stage,
  65                            struct prim_header *header )
  66 {
  67    const unsigned pos = draw_current_shader_position_output(stage->draw);
  68    struct offset_stage *offset = offset_stage(stage);
  69    float inv_det = 1.0f / header->det;
  70
  71    /* Window coords:
  72     */
  73    float *v0 = header->v[0]->data[pos];
  74    float *v1 = header->v[1]->data[pos];
  75    float *v2 = header->v[2]->data[pos];
  76
  77    /* edge vectors e = v0 - v2, f = v1 - v2 */
  78    float ex = v0[0] - v2[0];
  79    float ey = v0[1] - v2[1];
  80    float ez = v0[2] - v2[2];
  81    float fx = v1[0] - v2[0];
  82    float fy = v1[1] - v2[1];
  83    float fz = v1[2] - v2[2];
  84
  85    /* (a,b) = cross(e,f).xy */
  86    float a = ey*fz - ez*fy;
  87    float b = ez*fx - ex*fz;
  88
  89    float dzdx = fabsf(a * inv_det);
  90    float dzdy = fabsf(b * inv_det);
  91
  92    float zoffset = offset->units + MAX2(dzdx, dzdy) * offset->scale;
  93
  94    if (offset->clamp)
  95       zoffset = (offset->clamp < 0.0f) ? MAX2(zoffset, offset->clamp) :
  96                                          MIN2(zoffset, offset->clamp);
  97
  98    /*
  99     * Note: we're applying the offset and clamping per-vertex.
 100     * Ideally, the offset is applied per-fragment prior to fragment shading.
 101     */
 102    v0[2] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);
 103    v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);
 104    v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);
 105
 106    stage->next->tri( stage->next, header );
 107 }
 108
 109
 110 static void offset_tri( struct draw_stage *stage,
 111                         struct prim_header *header )
 112 {
 113    struct prim_header tmp;
 114
 115    tmp.det = header->det;
 116    tmp.flags = header->flags;
 117    tmp.pad = header->pad;
 118    tmp.v[0] = dup_vert(stage, header->v[0], 0);
 119    tmp.v[1] = dup_vert(stage, header->v[1], 1);
 120    tmp.v[2] = dup_vert(stage, header->v[2], 2);
 121
 122    do_offset_tri( stage, &tmp );
 123 }
 124
 125
 126 static void offset_first_tri( struct draw_stage *stage,
 127                               struct prim_header *header )
 128 {
 129    struct offset_stage *offset = offset_stage(stage);
 130    const struct pipe_rasterizer_state *rast = stage->draw->rasterizer;
 131    unsigned fill_mode = rast->fill_front;
 132    boolean do_offset;
 133
 134    if (rast->fill_back != rast->fill_front) {
 135       /* Need to check for back-facing triangle */
 136       boolean ccw = header->det < 0.0f;
 137       if (ccw != rast->front_ccw)
 138          fill_mode = rast->fill_back;
 139    }
 140
 141    /* Now determine if we need to do offsetting for the point/line/fill mode */
 142    switch (fill_mode) {
 143    case PIPE_POLYGON_MODE_FILL:
 144       do_offset = rast->offset_tri;
 145       break;
 146    case PIPE_POLYGON_MODE_LINE:
 147       do_offset = rast->offset_line;
 148       break;
 149    case PIPE_POLYGON_MODE_POINT:
 150       do_offset = rast->offset_point;
 151       break;
 152    default:
 153       assert(!"invalid fill_mode in offset_first_tri()");
 154       do_offset = rast->offset_tri;
 155    }
 156
 157    if (do_offset) {
 158       offset->scale = rast->offset_scale;
 159       offset->clamp = rast->offset_clamp;
 160       offset->units = (float) (rast->offset_units * stage->draw->mrd);
 161    }
 162    else {
 163       offset->scale = 0.0f;
 164       offset->clamp = 0.0f;
 165       offset->units = 0.0f;
 166    }
 167
 168
 169    stage->tri = offset_tri;
 170    stage->tri( stage, header );
 171 }
 172
 173
 174
 175
 176 static void offset_flush( struct draw_stage *stage,
 177                           unsigned flags )
 178 {
 179    stage->tri = offset_first_tri;
 180    stage->next->flush( stage->next, flags );
 181 }
 182
 183
 184 static void offset_reset_stipple_counter( struct draw_stage *stage )
 185 {
 186    stage->next->reset_stipple_counter( stage->next );
 187 }
 188
 189
 190 static void offset_destroy( struct draw_stage *stage )
 191 {
 192    draw_free_temp_verts( stage );
 193    FREE( stage );
 194 }
 195
 196
 197 /**
 198  * Create polygon offset drawing stage.
 199  */
 200 struct draw_stage *draw_offset_stage( struct draw_context *draw )
 201 {
 202    struct offset_stage *offset = CALLOC_STRUCT(offset_stage);
 203    if (offset == NULL)
 204       goto fail;
 205
 206    offset->stage.draw = draw;
 207    offset->stage.name = "offset";
 208    offset->stage.next = NULL;
 209    offset->stage.point = draw_pipe_passthrough_point;
 210    offset->stage.line = draw_pipe_passthrough_line;
 211    offset->stage.tri = offset_first_tri;
 212    offset->stage.flush = offset_flush;
 213    offset->stage.reset_stipple_counter = offset_reset_stipple_counter;
 214    offset->stage.destroy = offset_destroy;
 215
 216    if (!draw_alloc_temp_verts( &offset->stage, 3 ))
 217       goto fail;
 218
 219    return &offset->stage;
 220
 221 fail:
 222    if (offset)
 223       offset->stage.destroy( &offset->stage );
 224
 225    return NULL;
 226 }