149 lines
4.7 KiB
C
149 lines
4.7 KiB
C
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/*==========================================================================;
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*
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* Copyright (C) 1997 Microsoft Corporation. All Rights Reserved.
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*
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* File: clip.h
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* Content: Template for functions to clip by a frustum side
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*
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* The following symbol should be defined before included this file:
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* __CLIP_NAME - name for a function to clip triangles
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* __CLIP_LINE_NAME - name for a function to clip lines
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* __CLIP_W - if this functions are for Coord <= W. Otherwise they
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* are for 0 < Coord
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* __CLIP_COORD - should be hx, hy or hz
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* __CLIP_FLAG - clipping flag to set
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* __CLIP_GUARDBAND - defined when clipping by guardband window
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* __CLIP_SIGN - "-" if clipping by left or bottom sides of guard band
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* window
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* __CLIP_GBCOEF - coefficient to multiply W when clipping by guard band
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* window
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*
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* All these symbols are undefined at the end of this file
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***************************************************************************/
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//
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// Clipping for triangle
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//
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// Returns number of vertices in the clipped triangle
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//
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int
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RefClipper::__CLIP_NAME(RDClipVertex **inv, RDClipVertex **outv, int count)
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{
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int i;
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int out_count = 0;
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RDClipVertex *curr, *prev;
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D3DVALUE curr_inside;
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D3DVALUE prev_inside;
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prev = inv[count-1];
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curr = *inv++;
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#ifdef __CLIP_GUARDBAND
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prev_inside = __CLIP_SIGN(prev->m_clip_w * __CLIP_GBCOEF -
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prev->__CLIP_COORD);
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#else
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#ifdef __CLIP_W
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prev_inside = prev->m_clip_w - prev->__CLIP_COORD;
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#else
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prev_inside = prev->__CLIP_COORD;
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#endif
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#endif
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for (i = count; i; i--)
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{
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#ifdef __CLIP_GUARDBAND
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curr_inside = __CLIP_SIGN(curr->m_clip_w * __CLIP_GBCOEF -
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curr->__CLIP_COORD);
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#else
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#ifdef __CLIP_W
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curr_inside = curr->m_clip_w - curr->__CLIP_COORD;
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#else
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curr_inside = curr->__CLIP_COORD;
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#endif
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#endif
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// We interpolate always from the inside vertex to the outside vertex
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// to reduce precision problems
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if (FLOAT_LTZ(prev_inside))
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{ // first point is outside
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if (FLOAT_GEZ(curr_inside))
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{ // second point is inside
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// Find intersection and insert in into the output buffer
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outv[out_count] = GET_NEW_CLIP_VERTEX;
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outv[out_count]->m_qwFVF = prev->m_qwFVF;
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Interpolate(outv[out_count],
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curr, prev,
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(prev->m_clip & CLIPPED_ENABLE) | __CLIP_FLAG,
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curr_inside, curr_inside - prev_inside);
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out_count++;
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}
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}
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else
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{ // first point is inside - put it to the output buffer first
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outv[out_count++] = prev;
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if (FLOAT_LTZ(curr_inside))
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{ // second point is outside
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// Find intersection and put it to the output buffer
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outv[out_count] = GET_NEW_CLIP_VERTEX;
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outv[out_count]->m_qwFVF = prev->m_qwFVF;
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Interpolate(outv[out_count],
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prev, curr,
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__CLIP_FLAG,
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prev_inside, prev_inside - curr_inside);
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out_count++;
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}
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}
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prev = curr;
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curr = *inv++;
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prev_inside = curr_inside;
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}
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return out_count;
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}
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//-------------------------------------------------------------------------
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// Clipping for lines
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//
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// Returns 1 if the line is outside the frustum, 0 otherwise
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//
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int
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RefClipper::__CLIP_LINE_NAME(RDCLIPTRIANGLE *line)
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{
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D3DVALUE in1, in2;
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RDClipVertex outv;
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#ifdef __CLIP_GUARDBAND
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in1 = __CLIP_SIGN(line->v[0]->m_clip_w * __CLIP_GBCOEF -
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line->v[0]->__CLIP_COORD);
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in2 = __CLIP_SIGN(line->v[1]->m_clip_w * __CLIP_GBCOEF -
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line->v[1]->__CLIP_COORD);
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#else
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#ifdef __CLIP_W
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in1 = line->v[0]->m_clip_w - line->v[0]->__CLIP_COORD;
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in2 = line->v[1]->m_clip_w - line->v[1]->__CLIP_COORD;
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#else
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in1 = line->v[0]->__CLIP_COORD;
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in2 = line->v[1]->__CLIP_COORD;
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#endif
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#endif
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if (in1 < 0)
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{
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if (in2 < 0)
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return 1;
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Interpolate(&outv, line->v[0], line->v[1],
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__CLIP_FLAG, in1, in1 - in2);
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*line->v[0] = outv;
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}
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else
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{
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if (in2 < 0)
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{
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Interpolate(&outv, line->v[0], line->v[1],
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__CLIP_FLAG, in1, in1 - in2);
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*line->v[1] = outv;
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}
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}
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return 0;
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}
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#undef __CLIP_FLAG
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#undef __CLIP_COORD
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#undef __CLIP_NAME
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#undef __CLIP_LINE_NAME
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#undef __CLIP_W
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#undef __CLIP_SIGN
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#undef __CLIP_GBCOEF
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