98 lines
2.9 KiB
C
98 lines
2.9 KiB
C
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/* KallistiGL for KOS ##version##
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Near Z Clipper
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(c) Trilinear
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Trilinear@hotmail.com
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$Id: glclip.h,v 1.2 2002/06/28 04:47:02 axlen Exp $
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*/
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#ifndef __GLCLIP_H
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#define __GLCLIP_H
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#include <GL/gl.h>
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#include "glinternal.h"
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#define MAXZ 0.0001f /* if z is negative, it is behind the camera */
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inline void CopyV(gl_vertex_t *vertold, gl_vertex_t *vertnew) {
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/* memcpy(vertnew, vertold, sizeof(gl_vertex_t)); */
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vertnew->flags = vertold->flags;
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vertnew->x = vertold->x;
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vertnew->y = vertold->y;
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vertnew->z = vertold->z;
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vertnew->w = vertold->w;
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vertnew->u = vertold->u;
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vertnew->v = vertold->v;
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vertnew->argb = vertold->argb;
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vertnew->oargb = vertold->oargb;
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}
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inline void FindZ(gl_vertex_t *vertnew, gl_vertex_t *vert1, gl_vertex_t *vert2) {
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float diffz;
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/* z is indp variable because we know it changes, thus no div 0 error */
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vertnew->z = gl_frustum.znear;
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vertnew->w = vert1->w + (gl_frustum.znear-vert1->z)*(vert1->w - vert2->w)/(vert1->z - vert2->z);
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vertnew->x = vert1->x + (gl_frustum.znear-vert1->z)*(vert1->x - vert2->x)/(vert1->z - vert2->z);
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vertnew->y = vert1->y + (gl_frustum.znear-vert1->z)*(vert1->y - vert2->y)/(vert1->z - vert2->z);
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diffz = (vert1->z-vertnew->z)/(vert1->z-vert2->z);
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vertnew->u = (diffz)*vert2->u + (1.0f-diffz)*vert1->u;
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vertnew->v = (diffz)*vert2->v + (1.0f-diffz)*vert1->v;
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}
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inline int ZClipTex(gl_vertex_t *vert)
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/* returns 0 for full clip, 3 for triangle output and 4 for quad output
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based on sutherland-hodgeman clip algorithm */
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{
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int i,j;
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gl_vertex_t tempvert[4];
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if (vert[0].z < gl_frustum.znear || vert[1].z < gl_frustum.znear || vert[2].z < gl_frustum.znear) {/* one or more parts behind camera */
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j=0;
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CopyV(&vert[0],&vert[3]);/* copy first to next after last to make cyclic */
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for(i=0; i<3; i++) {
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if (vert[i].z >= gl_frustum.znear && vert[i+1].z >= gl_frustum.znear) { /* both in */
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CopyV(&vert[i],&tempvert[j]);
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j++;
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}else if (vert[i].z < gl_frustum.znear && vert[i+1].z >= gl_frustum.znear) {/* this out, next in */
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CopyV(&vert[i],&tempvert[j]);
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FindZ(&tempvert[j],&vert[i],&vert[i+1]);
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j++;
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}else if (vert[i].z >= gl_frustum.znear && vert[i+1].z < gl_frustum.znear) {/* this in, next out */
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CopyV(&vert[i],&tempvert[j]);
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CopyV(&vert[i+1],&tempvert[j+1]);
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FindZ(&tempvert[j+1],&vert[i],&vert[i+1]);
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j+=2;
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}/* both out, ignore */
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}
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switch (j) {
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case 3:
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CopyV(&tempvert[0],&vert[0]);
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CopyV(&tempvert[1],&vert[1]);
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CopyV(&tempvert[2],&vert[2]);
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return 3;
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case 4:
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CopyV(&tempvert[0],&vert[0]);
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CopyV(&tempvert[1],&vert[1]);
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CopyV(&tempvert[2],&vert[3]);
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CopyV(&tempvert[3],&vert[2]);
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return 4;
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}/* if j==0 we return 0 which we are about to do anyway */
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}else{/* is all in front of camera */
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return 3;
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}
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return 0;/* if it isn't one of the above it is an invalid poly or completely behind camera */
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}
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#endif /* __GLCLIP_H */
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