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/* Copyright (c) 1988 Regents of the University of California */ |
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|
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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#endif |
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|
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/* |
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* o_instance.c - routines for creating octrees for other octrees. |
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* |
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* 11/11/88 |
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*/ |
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|
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#include "standard.h" |
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|
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#include "object.h" |
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|
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#include "instance.h" |
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|
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#include "plocate.h" |
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|
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/* |
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* To determine if two cubes intersect: |
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* |
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* 1) Check to see if any vertices of first cube are inside the |
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* second (intersection). |
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* |
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* 2) Check to see if all vertices of first are to one side of |
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* second (no intersection). |
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* |
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* 3) Perform 1 and 2 with roles reversed. |
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* |
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* 4) Check to see if any portion of any edge of second is inside |
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* first (intersection). |
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* |
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* 5) If test 4 fails, we have no intersection. |
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* |
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* Note that if we were testing two boxes, we would need |
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* to check that neither had any edges inside the other to be sure. |
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* Since an octree is a volume rather than a surface, we will |
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* return a value of 2 if the cube is entirely within the octree. |
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*/ |
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|
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|
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o_instance(o, cu) /* determine if cubes intersect */ |
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OBJREC *o; |
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CUBE *cu; |
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{ |
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static char vstart[4] = {0, 3, 5, 6}; |
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FVECT cumin, cumax; |
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FVECT vert[8]; |
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FVECT v1, v2; |
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register INSTANCE *in; |
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int vloc, vout; |
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register int i, j; |
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/* get octree arguments */ |
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in = getinstance(o, GET_BOUNDS); |
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/* check if cube vertex in octree */ |
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for (j = 0; j < 3; j++) |
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cumax[j] = (cumin[j] = in->obj->scube.cuorg[j]) + |
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in->obj->scube.cusize; |
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vloc = ABOVE | BELOW; |
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vout = 0; |
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for (i = 0; i < 8; i++) { |
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for (j = 0; j < 3; j++) { |
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v1[j] = cu->cuorg[j]; |
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if (i & 1<<j) |
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v1[j] += cu->cusize; |
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} |
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multp3(v2, v1, in->b.xfm); |
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if (j = plocate(v2, cumin, cumax)) |
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vout++; |
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vloc &= j; |
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} |
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if (vout == 0) /* all inside */ |
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return(2); |
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if (vout < 8) /* some inside */ |
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return(1); |
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if (vloc) /* all to one side */ |
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return(0); |
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/* octree vertices in cube? */ |
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for (j = 0; j < 3; j++) |
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cumax[j] = (cumin[j] = cu->cuorg[j]) + cu->cusize; |
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vloc = ABOVE | BELOW; |
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for (i = 0; i < 8; i++) { |
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for (j = 0; j < 3; j++) { |
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v1[j] = in->obj->scube.cuorg[j]; |
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if (i & 1<<j) |
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v1[j] += in->obj->scube.cusize; |
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} |
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multp3(vert[i], v1, in->f.xfm); |
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if (j = plocate(vert[i], cumin, cumax)) |
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vloc &= j; |
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else |
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return(1); /* vertex inside */ |
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} |
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if (vloc) /* all to one side */ |
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return(0); |
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/* check edges */ |
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for (i = 0; i < 4; i++) |
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for (j = 0; j < 3; j++) { |
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/* clip modifies vertices! */ |
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VCOPY(v1, vert[vstart[i]]); |
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VCOPY(v2, vert[vstart[i] ^ 1<<j]); |
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if (clip(v1, v2, cumin, cumax)) |
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return(1); /* edge inside */ |
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} |
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|
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return(0); /* no intersection */ |
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} |