src/mesa/drivers/dri/i965/gen6_multisample_state.c

   1 /*
   2  * Copyright © 2012 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include "intel_batchbuffer.h"
  25
  26 #include "brw_context.h"
  27 #include "brw_defines.h"
  28
  29
  30 /**
  31  * 3DSTATE_MULTISAMPLE
  32  */
  33 void
  34 gen6_emit_3dstate_multisample(struct brw_context *brw,
  35                               unsigned num_samples)
  36 {
  37    struct intel_context *intel = &brw->intel;
  38
  39    uint32_t number_of_multisamples = 0;
  40    uint32_t sample_positions_3210 = 0;
  41    uint32_t sample_positions_7654 = 0;
  42
  43    switch (num_samples) {
  44    case 0:
  45    case 1:
  46       number_of_multisamples = MS_NUMSAMPLES_1;
  47       break;
  48    case 4:
  49       number_of_multisamples = MS_NUMSAMPLES_4;
  50       /* Sample positions:
  51        *   2 6 a e
  52        * 2   0
  53        * 6       1
  54        * a 2
  55        * e     3
  56        */
  57       sample_positions_3210 = 0xae2ae662;
  58       break;
  59    case 8:
  60       number_of_multisamples = MS_NUMSAMPLES_8;
  61       /* Sample positions are based on a solution to the "8 queens" puzzle.
  62        * Rationale: in a solution to the 8 queens puzzle, no two queens share
  63        * a row, column, or diagonal.  This is a desirable property for samples
  64        * in a multisampling pattern, because it ensures that the samples are
  65        * relatively uniformly distributed through the pixel.
  66        *
  67        * There are several solutions to the 8 queens puzzle (see
  68        * http://en.wikipedia.org/wiki/Eight_queens_puzzle).  This solution was
  69        * chosen because it has a queen close to the center; this should
  70        * improve the accuracy of centroid interpolation, since the hardware
  71        * implements centroid interpolation by choosing the centermost sample
  72        * that overlaps with the primitive being drawn.
  73        *
  74        * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
  75        * Programming Notes):
  76        *
  77        *     "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
  78        *     MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
  79        *     for 8X) must have monotonically increasing distance from the
  80        *     pixel center. This is required to get the correct centroid
  81        *     computation in the device."
  82        *
  83        * Sample positions:
  84        *   1 3 5 7 9 b d f
  85        * 1     5
  86        * 3           2
  87        * 5               6
  88        * 7 4
  89        * 9       0
  90        * b             3
  91        * d         1
  92        * f   7
  93        */
  94       sample_positions_3210 = 0xdbb39d79;
  95       sample_positions_7654 = 0x3ff55117;
  96       break;
  97    default:
  98       assert(!"Unrecognized num_samples in gen6_emit_3dstate_multisample");
  99       break;
 100    }
 101
 102    int len = intel->gen >= 7 ? 4 : 3;
 103    BEGIN_BATCH(len);
 104    OUT_BATCH(_3DSTATE_MULTISAMPLE << 16 | (len - 2));
 105    OUT_BATCH(MS_PIXEL_LOCATION_CENTER | number_of_multisamples);
 106    OUT_BATCH(sample_positions_3210);
 107    if (intel->gen >= 7)
 108       OUT_BATCH(sample_positions_7654);
 109    ADVANCE_BATCH();
 110 }
 111
 112
 113 /**
 114  * 3DSTATE_SAMPLE_MASK
 115  */
 116 void
 117 gen6_emit_3dstate_sample_mask(struct brw_context *brw,
 118                               unsigned num_samples, float coverage,
 119                               bool coverage_invert)
 120 {
 121    struct intel_context *intel = &brw->intel;
 122
 123    BEGIN_BATCH(2);
 124    OUT_BATCH(_3DSTATE_SAMPLE_MASK << 16 | (2 - 2));
 125    if (num_samples > 1) {
 126       int coverage_int = (int) (num_samples * coverage + 0.5);
 127       uint32_t coverage_bits = (1 << coverage_int) - 1;
 128       if (coverage_invert)
 129          coverage_bits ^= (1 << num_samples) - 1;
 130       OUT_BATCH(coverage_bits);
 131    } else {
 132       OUT_BATCH(1);
 133    }
 134    ADVANCE_BATCH();
 135 }
 136
 137
 138 static void upload_multisample_state(struct brw_context *brw)
 139 {
 140    struct intel_context *intel = &brw->intel;
 141    struct gl_context *ctx = &intel->ctx;
 142    float coverage = 1.0;
 143    float coverage_invert = false;
 144
 145    /* _NEW_BUFFERS */
 146    unsigned num_samples = ctx->DrawBuffer->Visual.samples;
 147
 148    /* _NEW_MULTISAMPLE */
 149    if (ctx->Multisample._Enabled && ctx->Multisample.SampleCoverage) {
 150       coverage = ctx->Multisample.SampleCoverageValue;
 151       coverage_invert = ctx->Multisample.SampleCoverageInvert;
 152    }
 153
 154    /* 3DSTATE_MULTISAMPLE is nonpipelined. */
 155    intel_emit_post_sync_nonzero_flush(intel);
 156
 157    gen6_emit_3dstate_multisample(brw, num_samples);
 158    gen6_emit_3dstate_sample_mask(brw, num_samples, coverage, coverage_invert);
 159 }
 160
 161
 162 const struct brw_tracked_state gen6_multisample_state = {
 163    .dirty = {
 164       .mesa = _NEW_BUFFERS |
 165               _NEW_MULTISAMPLE,
 166       .brw = BRW_NEW_CONTEXT,
 167       .cache = 0
 168    },
 169    .emit = upload_multisample_state
 170 };