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
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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 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_format.h"
  36 #include "util/u_math.h"
  37 #include "util/u_memory.h"
  38 #include "draw_pipe.h"
  39
  40
  41
  42 struct offset_stage {
  43    struct draw_stage stage;
  44
  45    float scale;
  46    float units;
  47    float clamp;
  48 };
  49
  50
  51
  52 static 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  */
  65 static 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, maxz, bias, mult;
  94
  95    mult = MAX2(dzdx, dzdy) * offset->scale;
  96
  97    if (stage->draw->floating_point_depth) {
  98       maxz = MAX3(v0[2], v1[2], v2[2]);
  99
 100       /**
 101        * XXX: TODO optimize this to quickly resolve a pow2 number through
 102        *      an exponent only operation.
 103        */
 104       bias = offset->units * util_fast_exp2(util_get_float32_exponent(maxz) - 23);
 105       zoffset = bias + mult;
 106    } else {
 107       zoffset = offset->units + mult;
 108    }
 109
 110    if (offset->clamp)
 111       zoffset = (offset->clamp < 0.0f) ? MAX2(zoffset, offset->clamp) :
 112                                          MIN2(zoffset, offset->clamp);
 113
 114    /*
 115     * Note: we're applying the offset and clamping per-vertex.
 116     * Ideally, the offset is applied per-fragment prior to fragment shading.
 117     */
 118    v0[2] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);
 119    v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);
 120    v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);
 121
 122    stage->next->tri( stage->next, header );
 123 }
 124
 125
 126 static void offset_tri( struct draw_stage *stage,
 127                         struct prim_header *header )
 128 {
 129    struct prim_header tmp;
 130
 131    tmp.det = header->det;
 132    tmp.flags = header->flags;
 133    tmp.pad = header->pad;
 134    tmp.v[0] = dup_vert(stage, header->v[0], 0);
 135    tmp.v[1] = dup_vert(stage, header->v[1], 1);
 136    tmp.v[2] = dup_vert(stage, header->v[2], 2);
 137
 138    do_offset_tri( stage, &tmp );
 139 }
 140
 141
 142 static void offset_first_tri( struct draw_stage *stage,
 143                               struct prim_header *header )
 144 {
 145    struct offset_stage *offset = offset_stage(stage);
 146    const struct pipe_rasterizer_state *rast = stage->draw->rasterizer;
 147    unsigned fill_mode = rast->fill_front;
 148    boolean do_offset;
 149
 150    if (rast->fill_back != rast->fill_front) {
 151       /* Need to check for back-facing triangle */
 152       boolean ccw = header->det < 0.0f;
 153       if (ccw != rast->front_ccw)
 154          fill_mode = rast->fill_back;
 155    }
 156
 157    /* Now determine if we need to do offsetting for the point/line/fill mode */
 158    switch (fill_mode) {
 159    case PIPE_POLYGON_MODE_FILL:
 160       do_offset = rast->offset_tri;
 161       break;
 162    case PIPE_POLYGON_MODE_LINE:
 163       do_offset = rast->offset_line;
 164       break;
 165    case PIPE_POLYGON_MODE_POINT:
 166       do_offset = rast->offset_point;
 167       break;
 168    default:
 169       assert(!"invalid fill_mode in offset_first_tri()");
 170       do_offset = rast->offset_tri;
 171    }
 172
 173    if (do_offset) {
 174       offset->scale = rast->offset_scale;
 175       offset->clamp = rast->offset_clamp;
 176
 177       /*
 178        * If depth is floating point, depth bias is calculated with respect
 179        * to the primitive's maximum Z value. Retain the original depth bias
 180        * value until that stage.
 181        */
 182       if (stage->draw->floating_point_depth) {
 183          offset->units = (float) rast->offset_units;
 184       } else {
 185          offset->units = (float) (rast->offset_units * stage->draw->mrd);
 186       }
 187    }
 188    else {
 189       offset->scale = 0.0f;
 190       offset->clamp = 0.0f;
 191       offset->units = 0.0f;
 192    }
 193
 194
 195    stage->tri = offset_tri;
 196    stage->tri( stage, header );
 197 }
 198
 199
 200
 201
 202 static void offset_flush( struct draw_stage *stage,
 203                           unsigned flags )
 204 {
 205    stage->tri = offset_first_tri;
 206    stage->next->flush( stage->next, flags );
 207 }
 208
 209
 210 static void offset_reset_stipple_counter( struct draw_stage *stage )
 211 {
 212    stage->next->reset_stipple_counter( stage->next );
 213 }
 214
 215
 216 static void offset_destroy( struct draw_stage *stage )
 217 {
 218    draw_free_temp_verts( stage );
 219    FREE( stage );
 220 }
 221
 222
 223 /**
 224  * Create polygon offset drawing stage.
 225  */
 226 struct draw_stage *draw_offset_stage( struct draw_context *draw )
 227 {
 228    struct offset_stage *offset = CALLOC_STRUCT(offset_stage);
 229    if (offset == NULL)
 230       goto fail;
 231
 232    offset->stage.draw = draw;
 233    offset->stage.name = "offset";
 234    offset->stage.next = NULL;
 235    offset->stage.point = draw_pipe_passthrough_point;
 236    offset->stage.line = draw_pipe_passthrough_line;
 237    offset->stage.tri = offset_first_tri;
 238    offset->stage.flush = offset_flush;
 239    offset->stage.reset_stipple_counter = offset_reset_stipple_counter;
 240    offset->stage.destroy = offset_destroy;
 241
 242    if (!draw_alloc_temp_verts( &offset->stage, 3 ))
 243       goto fail;
 244
 245    return &offset->stage;
 246
 247 fail:
 248    if (offset)
 249       offset->stage.destroy( &offset->stage );
 250
 251    return NULL;
 252 }