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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  polygon offset state

 *

 * \author  Keith Whitwell 

 * \author  Brian Paul

 */

#include "util/u_math.h"

#include "util/u_memory.h"

#include "draw_pipe.h"

struct offset_stage {

   struct draw_stage stage;

   float scale;

   float units;

   float clamp;

};

static INLINE struct offset_stage *offset_stage( struct draw_stage *stage )

{

   return (struct offset_stage *) stage;

}

/**

 * Offset tri Z.  Some hardware can handle this, but not usually when

 * doing unfilled rendering.

 */

static void do_offset_tri( struct draw_stage *stage,

			   struct prim_header *header )

{

   const unsigned pos = draw_current_shader_position_output(stage->draw);

   struct offset_stage *offset = offset_stage(stage);

   float inv_det = 1.0f / header->det;

   /* Window coords:

    */

   float *v0 = header->v[0]->data[pos];

   float *v1 = header->v[1]->data[pos];

   float *v2 = header->v[2]->data[pos];

   /* edge vectors e = v0 - v2, f = v1 - v2 */

   float ex = v0[0] - v2[0];

   float ey = v0[1] - v2[1];

   float ez = v0[2] - v2[2];

   float fx = v1[0] - v2[0];

   float fy = v1[1] - v2[1];

   float fz = v1[2] - v2[2];

   /* (a,b) = cross(e,f).xy */

   float a = ey*fz - ez*fy;

   float b = ez*fx - ex*fz;

   float dzdx = fabsf(a * inv_det);

   float dzdy = fabsf(b * inv_det);

   float zoffset = offset->units + MAX2(dzdx, dzdy) * offset->scale;

   if (offset->clamp)

      zoffset = (offset->clamp < 0.0f) ? MAX2(zoffset, offset->clamp) :

                                         MIN2(zoffset, offset->clamp);

   /*

    * Note: we're applying the offset and clamping per-vertex.

    * Ideally, the offset is applied per-fragment prior to fragment shading.

    */

   v0[2] = CLAMP(v0[2] + zoffset, 0.0f, 1.0f);

   v1[2] = CLAMP(v1[2] + zoffset, 0.0f, 1.0f);

   v2[2] = CLAMP(v2[2] + zoffset, 0.0f, 1.0f);

   stage->next->tri( stage->next, header );

}

static void offset_tri( struct draw_stage *stage,

			struct prim_header *header )

{

   struct prim_header tmp;

   tmp.det = header->det;

   tmp.flags = header->flags;

   tmp.pad = header->pad;

   tmp.v[0] = dup_vert(stage, header->v[0], 0);

   tmp.v[1] = dup_vert(stage, header->v[1], 1);

   tmp.v[2] = dup_vert(stage, header->v[2], 2);

   do_offset_tri( stage, &tmp );

}

static void offset_first_tri( struct draw_stage *stage,

			      struct prim_header *header )

{

   struct offset_stage *offset = offset_stage(stage);

   const struct pipe_rasterizer_state *rast = stage->draw->rasterizer;

   unsigned fill_mode = rast->fill_front;

   boolean do_offset;

   if (rast->fill_back != rast->fill_front) {

      /* Need to check for back-facing triangle */

      boolean ccw = header->det < 0.0f;

      if (ccw != rast->front_ccw)

         fill_mode = rast->fill_back;

   }

   /* Now determine if we need to do offsetting for the point/line/fill mode */

   switch (fill_mode) {

   case PIPE_POLYGON_MODE_FILL:

      do_offset = rast->offset_tri;

      break;

   case PIPE_POLYGON_MODE_LINE:

      do_offset = rast->offset_line;

      break;

   case PIPE_POLYGON_MODE_POINT:

      do_offset = rast->offset_point;

      break;

   default:

      assert(!"invalid fill_mode in offset_first_tri()");

      do_offset = rast->offset_tri;

   }

   if (do_offset) {

      offset->scale = rast->offset_scale;

      offset->clamp = rast->offset_clamp;

      offset->units = (float) (rast->offset_units * stage->draw->mrd);

   }

   else {

      offset->scale = 0.0f;

      offset->clamp = 0.0f;

      offset->units = 0.0f;

   }

   stage->tri = offset_tri;

   stage->tri( stage, header );

}

static void offset_flush( struct draw_stage *stage,

			  unsigned flags )

{

   stage->tri = offset_first_tri;

   stage->next->flush( stage->next, flags );

}

static void offset_reset_stipple_counter( struct draw_stage *stage )

{

   stage->next->reset_stipple_counter( stage->next );

}

static void offset_destroy( struct draw_stage *stage )

{

   draw_free_temp_verts( stage );

   FREE( stage );

}

/**

 * Create polygon offset drawing stage.

 */

struct draw_stage *draw_offset_stage( struct draw_context *draw )

{

   struct offset_stage *offset = CALLOC_STRUCT(offset_stage);

   if (offset == NULL)

      goto fail;

   offset->stage.draw = draw;

   offset->stage.name = "offset";

   offset->stage.next = NULL;

   offset->stage.point = draw_pipe_passthrough_point;

   offset->stage.line = draw_pipe_passthrough_line;

   offset->stage.tri = offset_first_tri;

   offset->stage.flush = offset_flush;

   offset->stage.reset_stipple_counter = offset_reset_stipple_counter;

   offset->stage.destroy = offset_destroy;

   if (!draw_alloc_temp_verts( &offset->stage, 3 ))

      goto fail;

   return &offset->stage;

fail:

   if (offset)

      offset->stage.destroy( &offset->stage );

   return NULL;

}