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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 "main/imports.h"
#include "pipe/p_defines.h"
#include "draw_private.h"
struct cull_stage {
struct draw_stage stage;
GLuint winding; /**< which winding(s) to cull (one of PIPE_WINDING_x) */
};
static INLINE struct cull_stage *cull_stage( struct draw_stage *stage )
{
return (struct cull_stage *)stage;
}
static void cull_begin( struct draw_stage *stage )
{
struct cull_stage *cull = cull_stage(stage);
cull->winding = stage->draw->setup.cull_mode;
stage->next->begin( stage->next );
}
static void cull_tri( struct draw_stage *stage,
struct prim_header *header )
{
/* Window coords: */
const GLfloat *v0 = header->v[0]->data[0];
const GLfloat *v1 = header->v[1]->data[0];
const GLfloat *v2 = header->v[2]->data[0];
/* edge vectors e = v0 - v2, f = v1 - v2 */
GLfloat ex = v0[0] - v2[0];
GLfloat ey = v0[1] - v2[1];
GLfloat fx = v1[0] - v2[0];
GLfloat 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 camera and triangle is
* counter-clockwise winding.
*/
GLuint winding = (header->det > 0) ? PIPE_WINDING_CCW : PIPE_WINDING_CW;
if ((winding & cull_stage(stage)->winding) == 0) {
/* triangle is not culled, pass to next stage */
stage->next->tri( stage->next, header );
}
}
}
static void cull_line( struct draw_stage *stage,
struct prim_header *header )
{
stage->next->line( stage->next, header );
}
static void cull_point( struct draw_stage *stage,
struct prim_header *header )
{
stage->next->point( stage->next, header );
}
static void cull_end( struct draw_stage *stage )
{
stage->next->end( stage->next );
}
/**
* Create a new polygon culling stage.
*/
struct draw_stage *draw_cull_stage( struct draw_context *draw )
{
struct cull_stage *cull = CALLOC_STRUCT(cull_stage);
draw_alloc_tmps( &cull->stage, 0 );
cull->stage.draw = draw;
cull->stage.next = NULL;
cull->stage.begin = cull_begin;
cull->stage.point = cull_point;
cull->stage.line = cull_line;
cull->stage.tri = cull_tri;
cull->stage.end = cull_end;
return &cull->stage;
}
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