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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 Drawing stage for polygon culling
*/
/* Authors: Keith Whitwell <keith@tungstengraphics.com>
*/
#include "util/u_memory.h"
#include "pipe/p_defines.h"
#include "draw_pipe.h"
struct cull_stage {
struct draw_stage stage;
unsigned cull_face; /**< which face(s) to cull (one of PIPE_FACE_x) */
unsigned front_ccw;
};
static INLINE struct cull_stage *cull_stage( struct draw_stage *stage )
{
return (struct cull_stage *)stage;
}
static void cull_tri( struct draw_stage *stage,
struct prim_header *header )
{
const unsigned pos = draw_current_shader_position_output(stage->draw);
/* Window coords: */
const float *v0 = header->v[0]->data[pos];
const float *v1 = header->v[1]->data[pos];
const float *v2 = header->v[2]->data[pos];
/* edge vectors: e = v0 - v2, f = v1 - v2 */
const float ex = v0[0] - v2[0];
const float ey = v0[1] - v2[1];
const float fx = v1[0] - v2[0];
const float fy = v1[1] - v2[1];
/* det = cross(e,f).z */
header->det = ex * fy - ey * fx;
if (header->det != 0) {
/* if det < 0 then Z points toward the camera and the triangle is
* counter-clockwise winding.
*/
unsigned ccw = (header->det < 0);
unsigned face = ((ccw == cull_stage(stage)->front_ccw) ?
PIPE_FACE_FRONT :
PIPE_FACE_BACK);
if ((face & cull_stage(stage)->cull_face) == 0) {
/* triangle is not culled, pass to next stage */
stage->next->tri( stage->next, header );
}
}
}
static void cull_first_tri( struct draw_stage *stage,
struct prim_header *header )
{
struct cull_stage *cull = cull_stage(stage);
cull->cull_face = stage->draw->rasterizer->cull_face;
cull->front_ccw = stage->draw->rasterizer->front_ccw;
stage->tri = cull_tri;
stage->tri( stage, header );
}
static void cull_flush( struct draw_stage *stage, unsigned flags )
{
stage->tri = cull_first_tri;
stage->next->flush( stage->next, flags );
}
static void cull_reset_stipple_counter( struct draw_stage *stage )
{
stage->next->reset_stipple_counter( stage->next );
}
static void cull_destroy( struct draw_stage *stage )
{
draw_free_temp_verts( stage );
FREE( stage );
}
/**
* Create a new polygon culling stage.
*/
struct draw_stage *draw_cull_stage( struct draw_context *draw )
{
struct cull_stage *cull = CALLOC_STRUCT(cull_stage);
if (cull == NULL)
goto fail;
if (!draw_alloc_temp_verts( &cull->stage, 0 ))
goto fail;
cull->stage.draw = draw;
cull->stage.name = "cull";
cull->stage.next = NULL;
cull->stage.point = draw_pipe_passthrough_point;
cull->stage.line = draw_pipe_passthrough_line;
cull->stage.tri = cull_first_tri;
cull->stage.flush = cull_flush;
cull->stage.reset_stipple_counter = cull_reset_stipple_counter;
cull->stage.destroy = cull_destroy;
return &cull->stage;
fail:
if (cull)
cull->stage.destroy( &cull->stage );
return NULL;
}
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