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path: root/src/gallium/drivers/llvmpipe/lp_quad_earlyz.c
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/**************************************************************************
 * 
 * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
 * All Rights Reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * 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.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
 * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 * 
 **************************************************************************/

/**
 * \brief  Quad early-z testing
 */

#include "pipe/p_defines.h"
#include "util/u_memory.h"
#include "lp_quad.h"
#include "lp_quad_pipe.h"


/**
 * All this stage does is compute the quad's Z values (which is normally
 * done by the shading stage).
 * The next stage will do the actual depth test.
 */
static void
earlyz_quad(
   struct quad_stage    *qs,
   struct quad_header   *quads[],
   unsigned nr )
{
   const float a0z = quads[0]->posCoef->a0[2];
   const float dzdx = quads[0]->posCoef->dadx[2];
   const float dzdy = quads[0]->posCoef->dady[2];
   unsigned i;

   for (i = 0; i < nr; i++) {
      const float fx = (float) quads[i]->input.x0;
      const float fy = (float) quads[i]->input.y0;
      const float z0 = a0z + dzdx * fx + dzdy * fy;

      quads[i]->output.depth[0] = z0;
      quads[i]->output.depth[1] = z0 + dzdx;
      quads[i]->output.depth[2] = z0 + dzdy;
      quads[i]->output.depth[3] = z0 + dzdx + dzdy;
   }

   qs->next->run( qs->next, quads, nr );
}

static void
earlyz_begin(
   struct quad_stage *qs )
{
   qs->next->begin( qs->next );
}

static void
earlyz_destroy(
   struct quad_stage *qs )
{
   FREE( qs );
}

struct quad_stage *
lp_quad_earlyz_stage(
   struct llvmpipe_context *llvmpipe )
{
   struct quad_stage *stage = CALLOC_STRUCT( quad_stage );

   stage->llvmpipe = llvmpipe;
   stage->begin = earlyz_begin;
   stage->run = earlyz_quad;
   stage->destroy = earlyz_destroy;

   return stage;
}