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/* Copyright (c) 1996 Regents of the University of California */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* Shading functions for anisotropic materials. |
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*/ |
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#include "copyright.h" |
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#include "ray.h" |
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#include "otypes.h" |
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#include "random.h" |
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extern double specthresh; /* specular sampling threshold */ |
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extern double specjitter; /* specular sampling jitter */ |
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extern int backvis; /* back faces visible? */ |
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#ifndef MAXITER |
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#define MAXITER 10 /* maximum # specular ray attempts */ |
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#endif |
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static agaussamp(), getacoords(); |
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/* |
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* This routine implements the anisotropic Gaussian |
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* model described by Ward in Siggraph `92 article. |
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double pdot; /* perturbed dot product */ |
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} ANISODAT; /* anisotropic material data */ |
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static void getacoords(); |
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static void agaussamp(); |
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static void |
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diraniso(cval, np, ldir, omega) /* compute source contribution */ |
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COLOR cval; /* returned coefficient */ |
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register ANISODAT *np; /* material data */ |
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} |
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int |
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m_aniso(m, r) /* shade ray that hit something anisotropic */ |
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register OBJREC *m; |
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register RAY *r; |
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} |
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static |
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static void |
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getacoords(r, np) /* set up coordinate system */ |
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RAY *r; |
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register ANISODAT *np; |
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} |
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static |
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static void |
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agaussamp(r, np) /* sample anisotropic gaussian specular */ |
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RAY *r; |
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register ANISODAT *np; |
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d = urand(ilhash(dimlist,ndims)+samplendx); |
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multisamp(rv, 2, d); |
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d = 2.0*PI * rv[0]; |
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cosp = cos(d) * np->u_alpha; |
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sinp = sin(d) * np->v_alpha; |
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cosp = tcos(d) * np->u_alpha; |
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sinp = tsin(d) * np->v_alpha; |
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d = sqrt(cosp*cosp + sinp*sinp); |
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cosp /= d; |
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sinp /= d; |
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d = urand(ilhash(dimlist,ndims)+1823+samplendx); |
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multisamp(rv, 2, d); |
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d = 2.0*PI * rv[0]; |
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cosp = cos(d) * np->u_alpha; |
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sinp = sin(d) * np->v_alpha; |
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cosp = tcos(d) * np->u_alpha; |
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sinp = tsin(d) * np->v_alpha; |
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d = sqrt(cosp*cosp + sinp*sinp); |
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cosp /= d; |
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sinp /= d; |
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else |
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d = sqrt(-log(rv[1]) / |
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(cosp*cosp/(np->u_alpha*np->u_alpha) + |
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sinp*sinp/(np->v_alpha*np->u_alpha))); |
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sinp*sinp/(np->v_alpha*np->v_alpha))); |
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for (i = 0; i < 3; i++) |
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sr.rdir[i] = np->prdir[i] + |
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d*(cosp*np->u[i] + sinp*np->v[i]); |