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