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