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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 <keith@tungstengraphics.com>
* \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;
};
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 = stage->draw->vs.position_output;
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;
/*
* 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);
float mrd = 1.0f / 65535.0f; /* XXX this depends on depthbuffer bits! */
offset->units = stage->draw->rasterizer->offset_units * mrd;
offset->scale = stage->draw->rasterizer->offset_scale;
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;
draw_alloc_temp_verts( &offset->stage, 3 );
offset->stage.draw = draw;
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;
return &offset->stage;
fail:
if (offset)
offset->stage.destroy( &offset->stage );
return NULL;
}
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