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  */
  58 static void wideline_line( struct draw_stage *stage,
  59                            struct prim_header *header )
  60 {
  61    /*const struct wideline_stage *wide = wideline_stage(stage);*/
  62    const unsigned pos = draw_current_shader_position_output(stage->draw);
  63    const float half_width = 0.5f * stage->draw->rasterizer->line_width;
  64
  65    struct prim_header tri;
  66
  67    struct vertex_header *v0 = dup_vert(stage, header->v[0], 0);
  68    struct vertex_header *v1 = dup_vert(stage, header->v[0], 1);
  69    struct vertex_header *v2 = dup_vert(stage, header->v[1], 2);
  70    struct vertex_header *v3 = dup_vert(stage, header->v[1], 3);
  71
  72    float *pos0 = v0->data[pos];
  73    float *pos1 = v1->data[pos];
  74    float *pos2 = v2->data[pos];
  75    float *pos3 = v3->data[pos];
  76
  77    const float dx = fabsf(pos0[0] - pos2[0]);
  78    const float dy = fabsf(pos0[1] - pos2[1]);
  79
  80    const boolean gl_rasterization_rules =
  81       stage->draw->rasterizer->gl_rasterization_rules;
  82
  83    /* small tweak to meet GL specification */
  84    const float bias = gl_rasterization_rules ? 0.125f : 0.0f;
  85
  86    /*
  87     * Draw wide line as a quad (two tris) by "stretching" the line along
  88     * X or Y.
  89     * We need to tweak coords in several ways to be conformant here.
  90     */
  91
  92    if (dx > dy) {
  93       /* x-major line */
  94       pos0[1] = pos0[1] - half_width - bias;
  95       pos1[1] = pos1[1] + half_width - bias;
  96       pos2[1] = pos2[1] - half_width - bias;
  97       pos3[1] = pos3[1] + half_width - bias;
  98       if (gl_rasterization_rules) {
  99          if (pos0[0] < pos2[0]) {
 100             /* left to right line */
 101             pos0[0] -= 0.5f;
 102             pos1[0] -= 0.5f;
 103             pos2[0] -= 0.5f;
 104             pos3[0] -= 0.5f;
 105          }
 106          else {
 107             /* right to left line */
 108             pos0[0] += 0.5f;
 109             pos1[0] += 0.5f;
 110             pos2[0] += 0.5f;
 111             pos3[0] += 0.5f;
 112          }
 113       }
 114    }
 115    else {
 116       /* y-major line */
 117       pos0[0] = pos0[0] - half_width + bias;
 118       pos1[0] = pos1[0] + half_width + bias;
 119       pos2[0] = pos2[0] - half_width + bias;
 120       pos3[0] = pos3[0] + half_width + bias;
 121       if (gl_rasterization_rules) {
 122          if (pos0[1] < pos2[1]) {
 123             /* top to bottom line */
 124             pos0[1] -= 0.5f;
 125             pos1[1] -= 0.5f;
 126             pos2[1] -= 0.5f;
 127             pos3[1] -= 0.5f;
 128          }
 129          else {
 130             /* bottom to top line */
 131             pos0[1] += 0.5f;
 132             pos1[1] += 0.5f;
 133             pos2[1] += 0.5f;
 134             pos3[1] += 0.5f;
 135          }
 136       }
 137    }
 138
 139    tri.det = header->det;  /* only the sign matters */
 140    tri.v[0] = v0;
 141    tri.v[1] = v2;
 142    tri.v[2] = v3;
 143    stage->next->tri( stage->next, &tri );
 144
 145    tri.v[0] = v0;
 146    tri.v[1] = v3;
 147    tri.v[2] = v1;
 148    stage->next->tri( stage->next, &tri );
 149 }
 150
 151
 152 static void wideline_first_line( struct draw_stage *stage,
 153                                  struct prim_header *header )
 154 {
 155    struct draw_context *draw = stage->draw;
 156    struct pipe_context *pipe = draw->pipe;
 157    const struct pipe_rasterizer_state *rast = draw->rasterizer;
 158    void *r;
 159
 160    /* Disable triangle culling, stippling, unfilled mode etc. */
 161    r = draw_get_rasterizer_no_cull(draw, rast->scissor, rast->flatshade);
 162    draw->suspend_flushing = TRUE;
 163    pipe->bind_rasterizer_state(pipe, r);
 164    draw->suspend_flushing = FALSE;
 165
 166    stage->line = wideline_line;
 167
 168    wideline_line(stage, header);
 169 }
 170
 171
 172 static void wideline_flush( struct draw_stage *stage, unsigned flags )
 173 {
 174    struct draw_context *draw = stage->draw;
 175    struct pipe_context *pipe = draw->pipe;
 176
 177    stage->line = wideline_first_line;
 178    stage->next->flush( stage->next, flags );
 179
 180    /* restore original rasterizer state */
 181    if (draw->rast_handle) {
 182       draw->suspend_flushing = TRUE;
 183       pipe->bind_rasterizer_state(pipe, draw->rast_handle);
 184       draw->suspend_flushing = FALSE;
 185    }
 186 }
 187
 188
 189 static void wideline_reset_stipple_counter( struct draw_stage *stage )
 190 {
 191    stage->next->reset_stipple_counter( stage->next );
 192 }
 193
 194
 195 static void wideline_destroy( struct draw_stage *stage )
 196 {
 197    draw_free_temp_verts( stage );
 198    FREE( stage );
 199 }
 200
 201
 202 struct draw_stage *draw_wide_line_stage( struct draw_context *draw )
 203 {
 204    struct wideline_stage *wide = CALLOC_STRUCT(wideline_stage);
 205    if (wide == NULL)
 206       goto fail;
 207
 208    wide->stage.draw = draw;
 209    wide->stage.name = "wide-line";
 210    wide->stage.next = NULL;
 211    wide->stage.point = draw_pipe_passthrough_point;
 212    wide->stage.line = wideline_first_line;
 213    wide->stage.tri = draw_pipe_passthrough_tri;
 214    wide->stage.flush = wideline_flush;
 215    wide->stage.reset_stipple_counter = wideline_reset_stipple_counter;
 216    wide->stage.destroy = wideline_destroy;
 217
 218    if (!draw_alloc_temp_verts( &wide->stage, 4 ))
 219       goto fail;
 220
 221    return &wide->stage;
 222
 223 fail:
 224    if (wide)
 225       wide->stage.destroy( &wide->stage );
 226
 227    return NULL;
 228 }