path: root/src/gallium/drivers/llvmpipe/lp_rast_tri.c

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 *
 * Copyright 2007-2009 VMware, Inc.
 * All Rights Reserved.
 *
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 * copy of this software and associated documentation files (the
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 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
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 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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/*
 * Rasterization for binned triangles within a tile
 */

#include <limits.h>
#include "util/u_math.h"
#include "lp_debug.h"
#include "lp_perf.h"
#include "lp_rast_priv.h"
#include "lp_tile_soa.h"


/**
 * Map an index in [0,15] to an x,y position, multiplied by 4.
 * This is used to get the position of each subtile in a 4x4
 * grid of edge step values.
 * Note: we can use some bit twiddling to compute these values instead
 * of using a look-up table, but there's no measurable performance
 * difference.
 */
static const int pos_table4[16][2] = {
   { 0, 0 },
   { 4, 0 },
   { 0, 4 },
   { 4, 4 },
   { 8, 0 },
   { 12, 0 },
   { 8, 4 },
   { 12, 4 },
   { 0, 8 },
   { 4, 8 },
   { 0, 12 },
   { 4, 12 },
   { 8, 8 },
   { 12, 8 },
   { 8, 12 },
   { 12, 12 }
};


static const int pos_table16[16][2] = {
   { 0, 0 },
   { 16, 0 },
   { 0, 16 },
   { 16, 16 },
   { 32, 0 },
   { 48, 0 },
   { 32, 16 },
   { 48, 16 },
   { 0, 32 },
   { 16, 32 },
   { 0, 48 },
   { 16, 48 },
   { 32, 32 },
   { 48, 32 },
   { 32, 48 },
   { 48, 48 }
};


/**
 * Shade all pixels in a 4x4 block.
 */
static void
block_full_4( struct lp_rasterizer_task *rast_task,
              const struct lp_rast_triangle *tri,
              int x, int y )
{
   lp_rast_shade_quads_all(rast_task->rast,
                           rast_task->thread_index,
                           &tri->inputs, 
                           x, y);
}


/**
 * Shade all pixels in a 16x16 block.
 */
static void
block_full_16( struct lp_rasterizer_task *rast_task,
               const struct lp_rast_triangle *tri,
               int x, int y )
{
   unsigned ix, iy;
   assert(x % 16 == 0);
   assert(y % 16 == 0);
   for (iy = 0; iy < 16; iy += 4)
      for (ix = 0; ix < 16; ix += 4)
	 block_full_4(rast_task, tri, x + ix, y + iy);
}


/**
 * Pass the 4x4 pixel block to the shader function.
 * Determination of which of the 16 pixels lies inside the triangle
 * will be done as part of the fragment shader.
 */
static void
do_block_4( struct lp_rasterizer_task *rast_task,
	    const struct lp_rast_triangle *tri,
	    int x, int y,
	    int c1,
	    int c2,
	    int c3 )
{
   lp_rast_shade_quads(rast_task->rast,
                       rast_task->thread_index,
                       &tri->inputs, 
                       x, y,
                       -c1, -c2, -c3);
}


/**
 * Evaluate a 16x16 block of pixels to determine which 4x4 subblocks are in/out
 * of the triangle's bounds.
 */
static void
do_block_16( struct lp_rasterizer_task *rast_task,
             const struct lp_rast_triangle *tri,
             int x, int y,
             int c1,
             int c2,
             int c3 )
{
   const int eo1 = tri->eo1 * 4;
   const int eo2 = tri->eo2 * 4;
   const int eo3 = tri->eo3 * 4;

   int i;

   assert(x % 16 == 0);
   assert(y % 16 == 0);

   for (i = 0; i < 16; i++) {
      int cx1 = c1 + (tri->inputs.step[0][i] * 4);
      int cx2 = c2 + (tri->inputs.step[1][i] * 4);
      int cx3 = c3 + (tri->inputs.step[2][i] * 4);

      if (cx1 + eo1 < 0 ||
          cx2 + eo2 < 0 ||
          cx3 + eo3 < 0) {
         /* the block is completely outside the triangle - nop */
         LP_COUNT(nr_empty_4);
      }
      else {
         int px = x + pos_table4[i][0];
         int py = y + pos_table4[i][1];
         /* Don't bother testing if the 4x4 block is entirely in/out of
          * the triangle.  It's a little faster to do it in the jit code.
          */
         LP_COUNT(nr_non_empty_4);
         do_block_4(rast_task, tri, px, py, cx1, cx2, cx3);
      }
   }
}


/**
 * Scan the tile in chunks and figure out which pixels to rasterize
 * for this triangle.
 */
void
lp_rast_triangle( struct lp_rasterizer *rast,
                  unsigned thread_index,
                  const union lp_rast_cmd_arg arg )
{
   struct lp_rasterizer_task *rast_task = &rast->tasks[thread_index];
   const struct lp_rast_triangle *tri = arg.triangle;

   int x = rast_task->x;
   int y = rast_task->y;
   unsigned i;

   int c1 = tri->c1 + tri->dx12 * y - tri->dy12 * x;
   int c2 = tri->c2 + tri->dx23 * y - tri->dy23 * x;
   int c3 = tri->c3 + tri->dx31 * y - tri->dy31 * x;

   int ei1 = tri->ei1 * 16;
   int ei2 = tri->ei2 * 16;
   int ei3 = tri->ei3 * 16;

   int eo1 = tri->eo1 * 16;
   int eo2 = tri->eo2 * 16;
   int eo3 = tri->eo3 * 16;

   LP_DBG(DEBUG_RAST, "lp_rast_triangle\n");

   /* Walk over the tile to build a list of 4x4 pixel blocks which will
    * be filled/shaded.  We do this at two granularities: 16x16 blocks
    * and then 4x4 blocks.
    */
   for (i = 0; i < 16; i++) {
      int cx1 = c1 + (tri->inputs.step[0][i] * 16);
      int cx2 = c2 + (tri->inputs.step[1][i] * 16);
      int cx3 = c3 + (tri->inputs.step[2][i] * 16);

      if (cx1 + eo1 < 0 ||
          cx2 + eo2 < 0 ||
          cx3 + eo3 < 0) {
         /* the block is completely outside the triangle - nop */
         LP_COUNT(nr_empty_16);
      }
      else {
         int px = x + pos_table16[i][0];
         int py = y + pos_table16[i][1];

         if (cx1 + ei1 > 0 &&
             cx2 + ei2 > 0 &&
             cx3 + ei3 > 0) {
            /* the block is completely inside the triangle */
            LP_COUNT(nr_fully_covered_16);
            block_full_16(rast_task, tri, px, py);
         }
         else {
            /* the block is partially in/out of the triangle */
            LP_COUNT(nr_partially_covered_16);
            do_block_16(rast_task, tri, px, py, cx1, cx2, cx3);
         }
      }
   }
}