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       number_of_multisamples = MS_NUMSAMPLES_1;
  46       break;
  47    case 4:
  48       number_of_multisamples = MS_NUMSAMPLES_4;
  49       /* Sample positions:
  50        *   2 6 a e
  51        * 2   0
  52        * 6       1
  53        * a 2
  54        * e     3
  55        */
  56       sample_positions_3210 = 0xae2ae662;
  57       break;
  58    case 8:
  59       number_of_multisamples = MS_NUMSAMPLES_8;
  60       /* Sample positions are based on a solution to the "8 queens" puzzle.
  61        * Rationale: in a solution to the 8 queens puzzle, no two queens share
  62        * a row, column, or diagonal.  This is a desirable property for samples
  63        * in a multisampling pattern, because it ensures that the samples are
  64        * relatively uniformly distributed through the pixel.
  65        *
  66        * There are several solutions to the 8 queens puzzle (see
  67        * http://en.wikipedia.org/wiki/Eight_queens_puzzle).  This solution was
  68        * chosen because it has a queen close to the center; this should
  69        * improve the accuracy of centroid interpolation, since the hardware
  70        * implements centroid interpolation by choosing the centermost sample
  71        * that overlaps with the primitive being drawn.
  72        *
  73        * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
  74        * Programming Notes):
  75        *
  76        *     "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
  77        *     MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
  78        *     for 8X) must have monotonically increasing distance from the
  79        *     pixel center. This is required to get the correct centroid
  80        *     computation in the device."
  81        *
  82        * Sample positions:
  83        *   1 3 5 7 9 b d f
  84        * 1     5
  85        * 3           2
  86        * 5               6
  87        * 7 4
  88        * 9       0
  89        * b             3
  90        * d         1
  91        * f   7
  92        */
  93       sample_positions_3210 = 0xdbb39d79;
  94       sample_positions_7654 = 0x3ff55117;
  95       break;
  96    default:
  97       assert(!"Unrecognized num_samples in gen6_emit_3dstate_multisample");
  98       break;
  99    }
 100
 101    int len = intel->gen >= 7 ? 4 : 3;
 102    BEGIN_BATCH(len);
 103    OUT_BATCH(_3DSTATE_MULTISAMPLE << 16 | (len - 2));
 104    OUT_BATCH(MS_PIXEL_LOCATION_CENTER | number_of_multisamples);
 105    OUT_BATCH(sample_positions_3210);
 106    if (intel->gen >= 7)
 107       OUT_BATCH(sample_positions_7654);
 108    ADVANCE_BATCH();
 109 }
 110
 111
 112 /**
 113  * 3DSTATE_SAMPLE_MASK
 114  */
 115 void
 116 gen6_emit_3dstate_sample_mask(struct brw_context *brw,
 117                               unsigned num_samples, float coverage,
 118                               bool coverage_invert)
 119 {
 120    struct intel_context *intel = &brw->intel;
 121
 122    /* TODO: 8x MSAA not implemented */
 123    assert(num_samples <= 4);
 124
 125    BEGIN_BATCH(2);
 126    OUT_BATCH(_3DSTATE_SAMPLE_MASK << 16 | (2 - 2));
 127    if (num_samples > 0) {
 128       int coverage_int = (int) (num_samples * coverage + 0.5);
 129       uint32_t coverage_bits = (1 << coverage_int) - 1;
 130       if (coverage_invert)
 131          coverage_bits ^= (1 << num_samples) - 1;
 132       OUT_BATCH(coverage_bits);
 133    } else {
 134       OUT_BATCH(1);
 135    }
 136    ADVANCE_BATCH();
 137 }
 138
 139
 140 static void upload_multisample_state(struct brw_context *brw)
 141 {
 142    struct intel_context *intel = &brw->intel;
 143    struct gl_context *ctx = &intel->ctx;
 144    float coverage = 1.0;
 145    float coverage_invert = false;
 146
 147    /* _NEW_BUFFERS */
 148    unsigned num_samples = ctx->DrawBuffer->Visual.samples;
 149
 150    /* _NEW_MULTISAMPLE */
 151    if (ctx->Multisample._Enabled && ctx->Multisample.SampleCoverage) {
 152       coverage = ctx->Multisample.SampleCoverageValue;
 153       coverage_invert = ctx->Multisample.SampleCoverageInvert;
 154    }
 155
 156    /* 3DSTATE_MULTISAMPLE is nonpipelined. */
 157    intel_emit_post_sync_nonzero_flush(intel);
 158
 159    gen6_emit_3dstate_multisample(brw, num_samples);
 160    gen6_emit_3dstate_sample_mask(brw, num_samples, coverage, coverage_invert);
 161 }
 162
 163
 164 const struct brw_tracked_state gen6_multisample_state = {
 165    .dirty = {
 166       .mesa = _NEW_BUFFERS |
 167               _NEW_MULTISAMPLE,
 168       .brw = BRW_NEW_CONTEXT,
 169       .cache = 0
 170    },
 171    .emit = upload_multisample_state
 172 };