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 #include "main/varray.h"
  35
  36 #include "vbo.h"
  37 #include "vbo_context.h"
  38
  39 #define UPDATE_MIN2(a, b) (a) = MIN2((a), (b))
  40 #define UPDATE_MAX2(a, b) (a) = MAX2((a), (b))
  41
  42 /*
  43  * Notes on primitive restart:
  44  * The code below is used when the driver does not support primitive
  45  * restart itself. (ctx->Const.PrimitiveRestartInSoftware == GL_TRUE)
  46  *
  47  * We map the index buffer, find the restart indexes, unmap
  48  * the index buffer then draw the sub-primitives delineated by the restarts.
  49  *
  50  * A couple possible optimizations:
  51  * 1. Save the list of sub-primitive (start, count) values in a list attached
  52  *    to the index buffer for re-use in subsequent draws.  The list would be
  53  *    invalidated when the contents of the buffer changed.
  54  * 2. If drawing triangle strips or quad strips, create a new index buffer
  55  *    that uses duplicated vertices to render the disjoint strips as one
  56  *    long strip.  We'd have to be careful to avoid using too much memory
  57  *    for this.
  58  *
  59  * Finally, some apps might perform better if they don't use primitive restart
  60  * at all rather than this fallback path.  Set MESA_EXTENSION_OVERRIDE to
  61  * "-GL_NV_primitive_restart" to test that.
  62  */
  63
  64
  65 struct sub_primitive
  66 {
  67    GLuint start;
  68    GLuint count;
  69    GLuint min_index;
  70    GLuint max_index;
  71 };
  72
  73
  74 /**
  75  * Scan the elements array to find restart indexes.  Return an array
  76  * of struct sub_primitive to indicate how to draw the sub-primitives
  77  * are delineated by the restart index.
  78  */
  79 static struct sub_primitive *
  80 find_sub_primitives(const void *elements, unsigned element_size,
  81                     unsigned start, unsigned end, unsigned restart_index,
  82                     unsigned *num_sub_prims)
  83 {
  84    const unsigned max_prims = end - start;
  85    struct sub_primitive *sub_prims;
  86    unsigned i, cur_start, cur_count;
  87    GLuint scan_index;
  88    unsigned scan_num;
  89
  90    sub_prims =
  91       malloc(max_prims * sizeof(struct sub_primitive));
  92
  93    if (!sub_prims) {
  94       *num_sub_prims = 0;
  95       return NULL;
  96    }
  97
  98    cur_start = start;
  99    cur_count = 0;
 100    scan_num = 0;
 101
 102 #define IB_INDEX_READ(TYPE, INDEX) (((const GL##TYPE *) elements)[INDEX])
 103
 104 #define SCAN_ELEMENTS(TYPE) \
 105    sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
 106    sub_prims[scan_num].max_index = 0; \
 107    for (i = start; i < end; i++) { \
 108       scan_index = IB_INDEX_READ(TYPE, i); \
 109       if (scan_index == restart_index) { \
 110          if (cur_count > 0) { \
 111             assert(scan_num < max_prims); \
 112             sub_prims[scan_num].start = cur_start; \
 113             sub_prims[scan_num].count = cur_count; \
 114             scan_num++; \
 115             sub_prims[scan_num].min_index = (GL##TYPE) 0xffffffff; \
 116             sub_prims[scan_num].max_index = 0; \
 117          } \
 118          cur_start = i + 1; \
 119          cur_count = 0; \
 120       } \
 121       else { \
 122          UPDATE_MIN2(sub_prims[scan_num].min_index, scan_index); \
 123          UPDATE_MAX2(sub_prims[scan_num].max_index, scan_index); \
 124          cur_count++; \
 125       } \
 126    } \
 127    if (cur_count > 0) { \
 128       assert(scan_num < max_prims); \
 129       sub_prims[scan_num].start = cur_start; \
 130       sub_prims[scan_num].count = cur_count; \
 131       scan_num++; \
 132    }
 133
 134    switch (element_size) {
 135    case 1:
 136       SCAN_ELEMENTS(ubyte);
 137       break;
 138    case 2:
 139       SCAN_ELEMENTS(ushort);
 140       break;
 141    case 4:
 142       SCAN_ELEMENTS(uint);
 143       break;
 144    default:
 145       assert(0 && "bad index_size in find_sub_primitives()");
 146    }
 147
 148 #undef SCAN_ELEMENTS
 149
 150    *num_sub_prims = scan_num;
 151
 152    return sub_prims;
 153 }
 154
 155
 156 /**
 157  * Handle primitive restart in software.
 158  *
 159  * This function breaks up calls into the driver so primitive restart
 160  * support is not required in the driver.
 161  */
 162 void
 163 vbo_sw_primitive_restart(struct gl_context *ctx,
 164                          const struct _mesa_prim *prims,
 165                          GLuint nr_prims,
 166                          const struct _mesa_index_buffer *ib)
 167 {
 168    GLuint prim_num;
 169    struct sub_primitive *sub_prims;
 170    struct sub_primitive *sub_prim;
 171    GLuint num_sub_prims;
 172    GLuint sub_prim_num;
 173    GLuint end_index;
 174    GLuint sub_end_index;
 175    GLuint restart_index = _mesa_primitive_restart_index(ctx, ib->type);
 176    struct _mesa_prim temp_prim;
 177    struct vbo_context *vbo = vbo_context(ctx);
 178    vbo_draw_func draw_prims_func = vbo->draw_prims;
 179    GLboolean map_ib = ib->obj->Name && !ib->obj->Pointer;
 180    void *ptr;
 181
 182    /* Find the sub-primitives. These are regions in the index buffer which
 183     * are split based on the primitive restart index value.
 184     */
 185    if (map_ib) {
 186       ctx->Driver.MapBufferRange(ctx, 0, ib->obj->Size, GL_MAP_READ_BIT,
 187                                  ib->obj);
 188    }
 189
 190    ptr = ADD_POINTERS(ib->obj->Pointer, ib->ptr);
 191
 192    sub_prims = find_sub_primitives(ptr, vbo_sizeof_ib_type(ib->type),
 193                                    0, ib->count, restart_index,
 194                                    &num_sub_prims);
 195
 196    if (map_ib) {
 197       ctx->Driver.UnmapBuffer(ctx, ib->obj);
 198    }
 199
 200    /* Loop over the primitives, and use the located sub-primitives to draw
 201     * each primitive with a break to implement each primitive restart.
 202     */
 203    for (prim_num = 0; prim_num < nr_prims; prim_num++) {
 204       end_index = prims[prim_num].start + prims[prim_num].count;
 205       memcpy(&temp_prim, &prims[prim_num], sizeof (temp_prim));
 206       /* Loop over the sub-primitives drawing sub-ranges of the primitive. */
 207       for (sub_prim_num = 0; sub_prim_num < num_sub_prims; sub_prim_num++) {
 208          sub_prim = &sub_prims[sub_prim_num];
 209          sub_end_index = sub_prim->start + sub_prim->count;
 210          if (prims[prim_num].start <= sub_prim->start) {
 211             temp_prim.start = MAX2(prims[prim_num].start, sub_prim->start);
 212             temp_prim.count = MIN2(sub_end_index, end_index) - temp_prim.start;
 213             if ((temp_prim.start == sub_prim->start) &&
 214                 (temp_prim.count == sub_prim->count)) {
 215                draw_prims_func(ctx, &temp_prim, 1, ib,
 216                                GL_TRUE, sub_prim->min_index, sub_prim->max_index,
 217                                NULL);
 218             } else {
 219                draw_prims_func(ctx, &temp_prim, 1, ib,
 220                                GL_FALSE, -1, -1,
 221                                NULL);
 222             }
 223          }
 224          if (sub_end_index >= end_index) {
 225             break;
 226          }
 227       }
 228    }
 229
 230    free(sub_prims);
 231 }
 232