src/mesa/drivers/dri/i965/gen6_clip_state.c

   1 /*
   2  * Copyright © 2009 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  * Authors:
  24  *    Eric Anholt <eric@anholt.net>
  25  *
  26  */
  27
  28 #include "brw_context.h"
  29 #include "brw_state.h"
  30 #include "brw_defines.h"
  31 #include "brw_util.h"
  32 #include "intel_batchbuffer.h"
  33 #include "main/fbobject.h"
  34 #include "main/framebuffer.h"
  35
  36 static void
  37 upload_clip_state(struct brw_context *brw)
  38 {
  39    struct gl_context *ctx = &brw->ctx;
  40    /* BRW_NEW_META_IN_PROGRESS */
  41    uint32_t dw1 = brw->meta_in_progress ? 0 : GEN6_CLIP_STATISTICS_ENABLE;
  42    uint32_t dw2 = 0;
  43
  44    /* _NEW_BUFFERS */
  45    struct gl_framebuffer *fb = ctx->DrawBuffer;
  46
  47    /* BRW_NEW_FS_PROG_DATA */
  48    if (brw->wm.prog_data->barycentric_interp_modes &
  49        BRW_WM_NONPERSPECTIVE_BARYCENTRIC_BITS) {
  50       dw2 |= GEN6_CLIP_NON_PERSPECTIVE_BARYCENTRIC_ENABLE;
  51    }
  52
  53    if (brw->gen >= 7)
  54       dw1 |= GEN7_CLIP_EARLY_CULL;
  55
  56    if (brw->gen == 7) {
  57       /* _NEW_POLYGON */
  58       if (ctx->Polygon._FrontBit == _mesa_is_user_fbo(fb))
  59          dw1 |= GEN7_CLIP_WINDING_CCW;
  60
  61       if (ctx->Polygon.CullFlag) {
  62          switch (ctx->Polygon.CullFaceMode) {
  63          case GL_FRONT:
  64             dw1 |= GEN7_CLIP_CULLMODE_FRONT;
  65             break;
  66          case GL_BACK:
  67             dw1 |= GEN7_CLIP_CULLMODE_BACK;
  68             break;
  69          case GL_FRONT_AND_BACK:
  70             dw1 |= GEN7_CLIP_CULLMODE_BOTH;
  71             break;
  72          default:
  73             unreachable("Should not get here: invalid CullFlag");
  74          }
  75       } else {
  76          dw1 |= GEN7_CLIP_CULLMODE_NONE;
  77       }
  78    }
  79
  80    if (brw->gen < 8 && !ctx->Transform.DepthClamp)
  81       dw2 |= GEN6_CLIP_Z_TEST;
  82
  83    /* _NEW_LIGHT */
  84    if (ctx->Light.ProvokingVertex == GL_FIRST_VERTEX_CONVENTION) {
  85       dw2 |=
  86          (0 << GEN6_CLIP_TRI_PROVOKE_SHIFT) |
  87          (1 << GEN6_CLIP_TRIFAN_PROVOKE_SHIFT) |
  88          (0 << GEN6_CLIP_LINE_PROVOKE_SHIFT);
  89    } else {
  90       dw2 |=
  91          (2 << GEN6_CLIP_TRI_PROVOKE_SHIFT) |
  92          (2 << GEN6_CLIP_TRIFAN_PROVOKE_SHIFT) |
  93          (1 << GEN6_CLIP_LINE_PROVOKE_SHIFT);
  94    }
  95
  96    /* _NEW_TRANSFORM */
  97    dw2 |= (ctx->Transform.ClipPlanesEnabled <<
  98            GEN6_USER_CLIP_CLIP_DISTANCES_SHIFT);
  99    if (ctx->Transform.ClipDepthMode == GL_ZERO_TO_ONE)
 100       dw2 |= GEN6_CLIP_API_D3D;
 101    else
 102       dw2 |= GEN6_CLIP_API_OGL;
 103
 104    dw2 |= GEN6_CLIP_GB_TEST;
 105
 106    /* We need to disable guardband clipping if the guardband (which we always
 107     * program to the maximum screen-space bounding box of 8K x 8K) will be
 108     * smaller than the viewport.
 109     *
 110     * Closely examining the clip determination formulas in the documentation
 111     * reveals that objects will be discarded entirely if they're outside the
 112     * (small) guardband, even if they're within the (large) viewport:
 113     *
 114     *     TR = TR_GB || TR_VPXY || TR_VPZ || TR_UC || TR_NEGW
 115     *     TA   = !TR && TA_GB && TA_VPZ && TA_NEGW
 116     *     MC = !(TA || TR)
 117     *
 118     * (TA is "Trivial Accept", TR is "Trivial Reject", MC is "Must Clip".)
 119     *
 120     * Disabling guardband clipping removes the TR_GB condition, which means
 121     * they'll be considered MC ("Must Clip") unless they're rejected for
 122     * some other reason.
 123     *
 124     * Note that there is no TA_VPXY condition.  If there were, objects entirely
 125     * inside a 16384x16384 viewport would be trivially accepted, breaking the
 126     * "objects must have a screenspace bounding box not exceeding 8K in the X
 127     * or Y direction" restriction.  Instead, they're clipped.
 128     */
 129    for (unsigned i = 0; i < ctx->Const.MaxViewports; i++) {
 130       if (ctx->ViewportArray[i].Width > 8192 ||
 131           ctx->ViewportArray[i].Height > 8192) {
 132          dw2 &= ~GEN6_CLIP_GB_TEST;
 133          break;
 134       }
 135    }
 136
 137    /* If the viewport dimensions are smaller than the drawable dimensions,
 138     * we have to disable guardband clipping prior to Gen8.  We always program
 139     * the guardband to a fixed size, which is almost always larger than the
 140     * viewport.  Any geometry which intersects the viewport but lies within
 141     * the guardband would bypass the 3D clipping stage, so it wouldn't be
 142     * clipped to the viewport.  Rendering would happen beyond the viewport,
 143     * but still inside the drawable.
 144     *
 145     * Gen8+ introduces a viewport extents test which restricts rendering to
 146     * the viewport, so we can ignore this restriction.
 147     */
 148    if (brw->gen < 8) {
 149       const float fb_width = (float)_mesa_geometric_width(fb);
 150       const float fb_height = (float)_mesa_geometric_height(fb);
 151
 152       for (unsigned i = 0; i < ctx->Const.MaxViewports; i++) {
 153          if (ctx->ViewportArray[i].X != 0 ||
 154              ctx->ViewportArray[i].Y != 0 ||
 155              ctx->ViewportArray[i].Width != fb_width ||
 156              ctx->ViewportArray[i].Height != fb_height) {
 157             dw2 &= ~GEN6_CLIP_GB_TEST;
 158             break;
 159          }
 160       }
 161    }
 162
 163    /* BRW_NEW_RASTERIZER_DISCARD */
 164    if (ctx->RasterDiscard) {
 165       dw2 |= GEN6_CLIP_MODE_REJECT_ALL;
 166       perf_debug("Rasterizer discard is currently implemented via the clipper; "
 167                  "%s be faster.\n", brw->gen >= 7 ? "using the SOL unit may" :
 168                  "having the GS not write primitives would likely");
 169    }
 170
 171    uint32_t enable;
 172    if (brw->primitive == _3DPRIM_RECTLIST)
 173       enable = 0;
 174    else
 175       enable = GEN6_CLIP_ENABLE;
 176
 177    BEGIN_BATCH(4);
 178    OUT_BATCH(_3DSTATE_CLIP << 16 | (4 - 2));
 179    OUT_BATCH(dw1);
 180    OUT_BATCH(enable |
 181              GEN6_CLIP_MODE_NORMAL |
 182              GEN6_CLIP_XY_TEST |
 183              dw2);
 184    OUT_BATCH(U_FIXED(0.125, 3) << GEN6_CLIP_MIN_POINT_WIDTH_SHIFT |
 185              U_FIXED(255.875, 3) << GEN6_CLIP_MAX_POINT_WIDTH_SHIFT |
 186              (_mesa_geometric_layers(fb) > 0 ? 0 : GEN6_CLIP_FORCE_ZERO_RTAINDEX) |
 187              ((ctx->Const.MaxViewports - 1) & GEN6_CLIP_MAX_VP_INDEX_MASK));
 188    ADVANCE_BATCH();
 189 }
 190
 191 const struct brw_tracked_state gen6_clip_state = {
 192    .dirty = {
 193       .mesa  = _NEW_BUFFERS |
 194                _NEW_LIGHT |
 195                _NEW_TRANSFORM,
 196       .brw   = BRW_NEW_CONTEXT |
 197                BRW_NEW_FS_PROG_DATA |
 198                BRW_NEW_META_IN_PROGRESS |
 199                BRW_NEW_RASTERIZER_DISCARD,
 200    },
 201    .emit = upload_clip_state,
 202 };
 203
 204 const struct brw_tracked_state gen7_clip_state = {
 205    .dirty = {
 206       .mesa  = _NEW_BUFFERS |
 207                _NEW_LIGHT |
 208                _NEW_POLYGON |
 209                _NEW_TRANSFORM,
 210       .brw   = BRW_NEW_CONTEXT |
 211                BRW_NEW_FS_PROG_DATA |
 212                BRW_NEW_META_IN_PROGRESS |
 213                BRW_NEW_RASTERIZER_DISCARD,
 214    },
 215    .emit = upload_clip_state,
 216 };