src/gallium/auxiliary/draw/draw_pipe_offset.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 VMware, Inc.
   4  * All Rights Reserved.
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  11  * permit persons to whom the Software is furnished to do so, subject to
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  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
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  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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  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
  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, 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(v0[2], v1[2], 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] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);
 124    v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);
 125    v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);
 126
 127    stage->next->tri( stage->next, header );
 128 }
 129
 130
 131 static 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
 147 static 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);
 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
 207 static 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
 215 static void offset_reset_stipple_counter( struct draw_stage *stage )
 216 {
 217    stage->next->reset_stipple_counter( stage->next );
 218 }
 219
 220
 221 static 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  */
 231 struct 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
 252 fail:
 253    if (offset)
 254       offset->stage.destroy( &offset->stage );
 255
 256    return NULL;
 257 }