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#ifndef lint |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* clip.c - routine to clip 3D line segments to a box. |
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*/ |
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/* ==================================================================== |
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* The Radiance Software License, Version 1.0 |
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* |
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* Copyright (c) 1990 - 2002 The Regents of the University of California, |
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* through Lawrence Berkeley National Laboratory. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* |
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* 3. The end-user documentation included with the redistribution, |
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* if any, must include the following acknowledgment: |
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* "This product includes Radiance software |
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* (http://radsite.lbl.gov/) |
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* developed by the Lawrence Berkeley National Laboratory |
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* (http://www.lbl.gov/)." |
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* Alternately, this acknowledgment may appear in the software itself, |
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* if and wherever such third-party acknowledgments normally appear. |
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* |
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* 4. The names "Radiance," "Lawrence Berkeley National Laboratory" |
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* and "The Regents of the University of California" must |
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* not be used to endorse or promote products derived from this |
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* software without prior written permission. For written |
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* permission, please contact [email protected]. |
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* |
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* 5. Products derived from this software may not be called "Radiance", |
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* nor may "Radiance" appear in their name, without prior written |
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* permission of Lawrence Berkeley National Laboratory. |
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* |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR |
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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* ==================================================================== |
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* |
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* This software consists of voluntary contributions made by many |
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* individuals on behalf of Lawrence Berkeley National Laboratory. For more |
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* information on Lawrence Berkeley National Laboratory, please see |
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* <http://www.lbl.gov/>. |
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*/ |
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#include "fvect.h" |
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#include "plocate.h" |
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#define MAXITER 6 /* maximum possible number of iterations */ |
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int |
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clip(ep1, ep2, min, max) /* clip a line segment to a box */ |
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FLOAT *ep1, *ep2; |
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FVECT min, max; |
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{ |
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int itlim = MAXITER; |
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int loc1, loc2; |
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int accept; |
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FLOAT *dp; |
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double d; |
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register int i, j; |
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/* |
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* The Cohen-Sutherland algorithm is used to determine |
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* what part (if any) of the given line segment is contained |
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* in the box specified by the min and max vectors. |
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* The routine returns non-zero if any segment is left. |
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*/ |
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loc1 = plocate(ep1, min, max); |
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loc2 = plocate(ep2, min, max); |
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/* check for trivial accept and reject */ |
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/* trivial accept is both points inside */ |
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/* trivial reject is both points to one side */ |
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while (!((accept = !(loc1 | loc2)) || (loc1 & loc2))) { |
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if (itlim-- <= 0) /* past theoretical limit? */ |
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return(0); /* quit fooling around */ |
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if (!loc1) { /* make sure first point is outside */ |
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dp = ep1; ep1 = ep2; ep2 = dp; |
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i = loc1; loc1 = loc2; loc2 = i; |
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} |
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for (i = 0; i < 3; i++) { /* chop segment */ |
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if (loc1 & position(i) & BELOW) { |
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d = (min[i] - ep1[i])/(ep2[i] - ep1[i]); |
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ep1[i] = min[i]; |
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} else if (loc1 & position(i) & ABOVE) { |
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d = (max[i] - ep1[i])/(ep2[i] - ep1[i]); |
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ep1[i] = max[i]; |
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} else |
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continue; |
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for (j = 0; j < 3; j++) |
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if (j != i) |
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ep1[j] += (ep2[j] - ep1[j])*d; |
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break; |
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} |
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loc1 = plocate(ep1, min, max); |
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} |
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return(accept); |
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} |