src/gallium/auxiliary/draw/draw_pipe_wide_line.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 VMware, Inc.
   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 VMWARE 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 /* Authors:  Keith Whitwell <keithw@vmware.com>
  29  */
  30
  31 #include "pipe/p_context.h"
  32 #include "pipe/p_defines.h"
  33 #include "pipe/p_shader_tokens.h"
  34 #include "util/u_math.h"
  35 #include "util/u_memory.h"
  36 #include "draw_private.h"
  37 #include "draw_pipe.h"
  38
  39
  40 struct wideline_stage {
  41    struct draw_stage stage;
  42 };
  43
  44
  45 /**
  46  * Draw a wide line by drawing a quad (two triangles).
  47  */
  48 static void wideline_line( struct draw_stage *stage,
  49                            struct prim_header *header )
  50 {
  51    const unsigned pos = draw_current_shader_position_output(stage->draw);
  52    const float half_width = 0.5f * stage->draw->rasterizer->line_width;
  53
  54    struct prim_header tri;
  55
  56    struct vertex_header *v0 = dup_vert(stage, header->v[0], 0);
  57    struct vertex_header *v1 = dup_vert(stage, header->v[0], 1);
  58    struct vertex_header *v2 = dup_vert(stage, header->v[1], 2);
  59    struct vertex_header *v3 = dup_vert(stage, header->v[1], 3);
  60
  61    float *pos0 = v0->data[pos];
  62    float *pos1 = v1->data[pos];
  63    float *pos2 = v2->data[pos];
  64    float *pos3 = v3->data[pos];
  65
  66    const float dx = fabsf(pos0[0] - pos2[0]);
  67    const float dy = fabsf(pos0[1] - pos2[1]);
  68
  69    const boolean half_pixel_center =
  70       stage->draw->rasterizer->half_pixel_center;
  71
  72    /* small tweak to meet GL specification */
  73    const float bias = half_pixel_center ? 0.125f : 0.0f;
  74
  75    /*
  76     * Draw wide line as a quad (two tris) by "stretching" the line along
  77     * X or Y.
  78     * We need to tweak coords in several ways to be conformant here.
  79     */
  80
  81    if (dx > dy) {
  82       /* x-major line */
  83       pos0[1] = pos0[1] - half_width - bias;
  84       pos1[1] = pos1[1] + half_width - bias;
  85       pos2[1] = pos2[1] - half_width - bias;
  86       pos3[1] = pos3[1] + half_width - bias;
  87       if (half_pixel_center) {
  88          if (pos0[0] < pos2[0]) {
  89             /* left to right line */
  90             pos0[0] -= 0.5f;
  91             pos1[0] -= 0.5f;
  92             pos2[0] -= 0.5f;
  93             pos3[0] -= 0.5f;
  94          }
  95          else {
  96             /* right to left line */
  97             pos0[0] += 0.5f;
  98             pos1[0] += 0.5f;
  99             pos2[0] += 0.5f;
 100             pos3[0] += 0.5f;
 101          }
 102       }
 103    }
 104    else {
 105       /* y-major line */
 106       pos0[0] = pos0[0] - half_width + bias;
 107       pos1[0] = pos1[0] + half_width + bias;
 108       pos2[0] = pos2[0] - half_width + bias;
 109       pos3[0] = pos3[0] + half_width + bias;
 110       if (half_pixel_center) {
 111          if (pos0[1] < pos2[1]) {
 112             /* top to bottom line */
 113             pos0[1] -= 0.5f;
 114             pos1[1] -= 0.5f;
 115             pos2[1] -= 0.5f;
 116             pos3[1] -= 0.5f;
 117          }
 118          else {
 119             /* bottom to top line */
 120             pos0[1] += 0.5f;
 121             pos1[1] += 0.5f;
 122             pos2[1] += 0.5f;
 123             pos3[1] += 0.5f;
 124          }
 125       }
 126    }
 127
 128    tri.det = header->det;  /* only the sign matters */
 129    tri.v[0] = v0;
 130    tri.v[1] = v2;
 131    tri.v[2] = v3;
 132    stage->next->tri( stage->next, &tri );
 133
 134    tri.v[0] = v0;
 135    tri.v[1] = v3;
 136    tri.v[2] = v1;
 137    stage->next->tri( stage->next, &tri );
 138 }
 139
 140
 141 static void wideline_first_line( struct draw_stage *stage,
 142                                  struct prim_header *header )
 143 {
 144    struct draw_context *draw = stage->draw;
 145    struct pipe_context *pipe = draw->pipe;
 146    const struct pipe_rasterizer_state *rast = draw->rasterizer;
 147    void *r;
 148
 149    /* Disable triangle culling, stippling, unfilled mode etc. */
 150    r = draw_get_rasterizer_no_cull(draw, rast->scissor, rast->flatshade);
 151    draw->suspend_flushing = TRUE;
 152    pipe->bind_rasterizer_state(pipe, r);
 153    draw->suspend_flushing = FALSE;
 154
 155    stage->line = wideline_line;
 156
 157    wideline_line(stage, header);
 158 }
 159
 160
 161 static void wideline_flush( struct draw_stage *stage, unsigned flags )
 162 {
 163    struct draw_context *draw = stage->draw;
 164    struct pipe_context *pipe = draw->pipe;
 165
 166    stage->line = wideline_first_line;
 167    stage->next->flush( stage->next, flags );
 168
 169    /* restore original rasterizer state */
 170    if (draw->rast_handle) {
 171       draw->suspend_flushing = TRUE;
 172       pipe->bind_rasterizer_state(pipe, draw->rast_handle);
 173       draw->suspend_flushing = FALSE;
 174    }
 175 }
 176
 177
 178 static void wideline_reset_stipple_counter( struct draw_stage *stage )
 179 {
 180    stage->next->reset_stipple_counter( stage->next );
 181 }
 182
 183
 184 static void wideline_destroy( struct draw_stage *stage )
 185 {
 186    draw_free_temp_verts( stage );
 187    FREE( stage );
 188 }
 189
 190
 191 struct draw_stage *draw_wide_line_stage( struct draw_context *draw )
 192 {
 193    struct wideline_stage *wide = CALLOC_STRUCT(wideline_stage);
 194    if (!wide)
 195       goto fail;
 196
 197    wide->stage.draw = draw;
 198    wide->stage.name = "wide-line";
 199    wide->stage.next = NULL;
 200    wide->stage.point = draw_pipe_passthrough_point;
 201    wide->stage.line = wideline_first_line;
 202    wide->stage.tri = draw_pipe_passthrough_tri;
 203    wide->stage.flush = wideline_flush;
 204    wide->stage.reset_stipple_counter = wideline_reset_stipple_counter;
 205    wide->stage.destroy = wideline_destroy;
 206
 207    if (!draw_alloc_temp_verts( &wide->stage, 4 ))
 208       goto fail;
 209
 210    return &wide->stage;
 211
 212 fail:
 213    if (wide)
 214       wide->stage.destroy( &wide->stage );
 215
 216    return NULL;
 217 }