src/mesa/vbo/vbo_primitive_restart.c

   1 /*
   2  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   3  * All Rights Reserved.
   4  *
   5  * Copyright © 2012 Intel Corporation
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the next
  15  * paragraph) shall be included in all copies or substantial portions of the
  16  * Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  21  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  24  * IN THE SOFTWARE.
  25  *
  26  * Authors:
  27  *    Jordan Justen <jordan.l.justen@intel.com>
  28  *
  29  */
  30
  31 #include "main/imports.h"
  32 #include "main/bufferobj.h"
  33 #include "main/macros.h"
  34
  35 #include "vbo.h"
  36 #include "vbo_context.h"
  37
  38 #define UPDATE_MIN2(a, b) (a) = MIN2((a), (b))
  39 #define UPDATE_MAX2(a, b) (a) = MAX2((a), (b))
  40
  41 /*
  42  * Notes on primitive restart:
  43  * The code below is used when the driver does not support primitive
  44  * restart itself. (ctx->Const.PrimitiveRestartInSoftware == GL_TRUE)
  45  *
  46  * We map the index buffer, find the restart indexes, unmap
  47  * the index buffer then draw the sub-primitives delineated by the restarts.
  48  *
  49  * A couple possible optimizations:
  50  * 1. Save the list of sub-primitive (start, count) values in a list attached
  51  *    to the index buffer for re-use in subsequent draws.  The list would be
  52  *    invalidated when the contents of the buffer changed.
  53  * 2. If drawing triangle strips or quad strips, create a new index buffer
  54  *    that uses duplicated vertices to render the disjoint strips as one
  55  *    long strip.  We'd have to be careful to avoid using too much memory
  56  *    for this.
  57  *
  58  * Finally, some apps might perform better if they don't use primitive restart
  59  * at all rather than this fallback path.  Set MESA_EXTENSION_OVERRIDE to
  60  * "-GL_NV_primitive_restart" to test that.
  61  */
  62
  63
  64 struct sub_primitive
  65 {
  66    GLuint start;
  67    GLuint count;
  68    GLuint min_index;
  69    GLuint max_index;
  70 };
  71
  72
  73 /**
  74  * Scan the elements array to find restart indexes.  Return an array
  75  * of struct sub_primitive to indicate how to draw the sub-primitives
  76  * are delineated by the restart index.
  77  */
  78 static struct sub_primitive *
  79 find_sub_primitives(const void *elements, unsigned element_size,
  80                     unsigned start, unsigned end, unsigned restart_index,
  81                     unsigned *num_sub_prims)
  82 {
  83    const unsigned max_prims = end - start;
  84    struct sub_primitive *sub_prims;
  85    unsigned i, cur_start, cur_count;
  86    GLuint scan_index;
  87    unsigned scan_num;
  88
  89    sub_prims =
  90       malloc(max_prims * sizeof(struct sub_primitive));
  91
  92    if (!sub_prims) {
  93       *num_sub_prims = 0;
  94       return NULL;
  95    }
  96
  97    cur_start = start;
  98    cur_count = 0;
  99    scan_num = 0;
 100
 101 #define IB_INDEX_READ(TYPE, INDEX) (((const GL##TYPE *) elements)[INDEX])
 102
 103 #define SCAN_ELEMENTS(TYPE) \
 104    sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
 105    sub_prims[scan_num].max_index = 0; \
 106    for (i = start; i < end; i++) { \
 107       scan_index = IB_INDEX_READ(TYPE, i); \
 108       if (scan_index == restart_index) { \
 109          if (cur_count > 0) { \
 110             assert(scan_num < max_prims); \
 111             sub_prims[scan_num].start = cur_start; \
 112             sub_prims[scan_num].count = cur_count; \
 113             scan_num++; \
 114             sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
 115             sub_prims[scan_num].max_index = 0; \
 116          } \
 117          cur_start = i + 1; \
 118          cur_count = 0; \
 119       } \
 120       else { \
 121          UPDATE_MIN2(sub_prims[scan_num].min_index, scan_index); \
 122          UPDATE_MAX2(sub_prims[scan_num].max_index, scan_index); \
 123          cur_count++; \
 124       } \
 125    } \
 126    if (cur_count > 0) { \
 127       assert(scan_num < max_prims); \
 128       sub_prims[scan_num].start = cur_start; \
 129       sub_prims[scan_num].count = cur_count; \
 130       scan_num++; \
 131    }
 132
 133    switch (element_size) {
 134    case 1:
 135       SCAN_ELEMENTS(ubyte);
 136       break;
 137    case 2:
 138       SCAN_ELEMENTS(ushort);
 139       break;
 140    case 4:
 141       SCAN_ELEMENTS(uint);
 142       break;
 143    default:
 144       assert(0 && "bad index_size in find_sub_primitives()");
 145    }
 146
 147 #undef SCAN_ELEMENTS
 148
 149    *num_sub_prims = scan_num;
 150
 151    return sub_prims;
 152 }
 153
 154
 155 /**
 156  * Handle primitive restart in software.
 157  *
 158  * This function breaks up calls into the driver so primitive restart
 159  * support is not required in the driver.
 160  */
 161 void
 162 vbo_sw_primitive_restart(struct gl_context *ctx,
 163                          const struct _mesa_prim *prims,
 164                          GLuint nr_prims,
 165                          const struct _mesa_index_buffer *ib)
 166 {
 167    GLuint prim_num;
 168    struct sub_primitive *sub_prims;
 169    struct sub_primitive *sub_prim;
 170    GLuint num_sub_prims;
 171    GLuint sub_prim_num;
 172    GLuint end_index;
 173    GLuint sub_end_index;
 174    GLuint restart_index = ctx->Array._RestartIndex;
 175    struct _mesa_prim temp_prim;
 176    struct vbo_context *vbo = vbo_context(ctx);
 177    vbo_draw_func draw_prims_func = vbo->draw_prims;
 178    GLboolean map_ib = ib->obj->Name && !ib->obj->Pointer;
 179    void *ptr;
 180
 181    /* Find the sub-primitives. These are regions in the index buffer which
 182     * are split based on the primitive restart index value.
 183     */
 184    if (map_ib) {
 185       ctx->Driver.MapBufferRange(ctx, 0, ib->obj->Size, GL_MAP_READ_BIT,
 186                                  ib->obj);
 187    }
 188
 189    ptr = ADD_POINTERS(ib->obj->Pointer, ib->ptr);
 190
 191    sub_prims = find_sub_primitives(ptr, vbo_sizeof_ib_type(ib->type),
 192                                    0, ib->count, restart_index,
 193                                    &num_sub_prims);
 194
 195    if (map_ib) {
 196       ctx->Driver.UnmapBuffer(ctx, ib->obj);
 197    }
 198
 199    /* Loop over the primitives, and use the located sub-primitives to draw
 200     * each primitive with a break to implement each primitive restart.
 201     */
 202    for (prim_num = 0; prim_num < nr_prims; prim_num++) {
 203       end_index = prims[prim_num].start + prims[prim_num].count;
 204       memcpy(&temp_prim, &prims[prim_num], sizeof (temp_prim));
 205       /* Loop over the sub-primitives drawing sub-ranges of the primitive. */
 206       for (sub_prim_num = 0; sub_prim_num < num_sub_prims; sub_prim_num++) {
 207          sub_prim = &sub_prims[sub_prim_num];
 208          sub_end_index = sub_prim->start + sub_prim->count;
 209          if (prims[prim_num].start <= sub_prim->start) {
 210             temp_prim.start = MAX2(prims[prim_num].start, sub_prim->start);
 211             temp_prim.count = MIN2(sub_end_index, end_index) - temp_prim.start;
 212             if ((temp_prim.start == sub_prim->start) &&
 213                 (temp_prim.count == sub_prim->count)) {
 214                draw_prims_func(ctx, &temp_prim, 1, ib,
 215                                GL_TRUE, sub_prim->min_index, sub_prim->max_index,
 216                                NULL);
 217             } else {
 218                draw_prims_func(ctx, &temp_prim, 1, ib,
 219                                GL_FALSE, -1, -1,
 220                                NULL);
 221             }
 222          }
 223          if (sub_end_index >= end_index) {
 224             break;
 225          }
 226       }
 227    }
 228
 229    free(sub_prims);
 230 }
 231