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/* Copyright (c) 1997 Silicon Graphics, Inc. */ |
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/* Copyright (c) 1998 Silicon Graphics, Inc. */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ SGI"; |
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int |
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npixels(vp, hr, vr, hp, bi) /* compute appropriate number to evaluate */ |
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npixels(vp, hr, vr, hp, bi) /* compute appropriate nrays to evaluate */ |
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register VIEW *vp; |
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int hr, vr; |
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HOLO *hp; |
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{ |
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VIEW vrev; |
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GCOORD gc[2]; |
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FVECT cp[4], ip[4]; |
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double af, ab; |
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FVECT cp[4], ip[4], pf, pb; |
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double af, ab, sf2, sb2, dfb2, df2, db2, penalty; |
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register int i; |
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/* compute cell corners in image */ |
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if (!hdbcoord(gc, hp, bi)) |
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error(CONSISTENCY, "bad beam index in npixels"); |
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hdcell(cp, hp, gc+1); /* find cell on front image */ |
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for (i = 0; i < 4; i++) { |
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for (i = 3; i--; ) /* compute front center */ |
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pf[i] = 0.5*(cp[0][i] + cp[2][i]); |
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sf2 = 0.25*dist2(cp[0], cp[2]); /* compute half diagonal length */ |
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for (i = 0; i < 4; i++) { /* compute visible quad */ |
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viewloc(ip[i], vp, cp[i]); |
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if (ip[i][2] < 0.) { |
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af = 0; |
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(ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]); |
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af += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) - |
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(ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]); |
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if (af >= 0) af *= 0.5; |
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else af *= -0.5; |
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af *= af >= 0 ? 0.5 : -0.5; |
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getback: |
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copystruct(&vrev, vp); /* compute reverse view */ |
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for (i = 0; i < 3; i++) { |
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vrev.vvec[i] = -vp->vvec[i]; |
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} |
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hdcell(cp, hp, gc); /* find cell on back image */ |
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for (i = 0; i < 4; i++) { |
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for (i = 3; i--; ) /* compute rear center */ |
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pb[i] = 0.5*(cp[0][i] + cp[2][i]); |
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sb2 = 0.25*dist2(cp[0], cp[2]); /* compute half diagonal length */ |
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for (i = 0; i < 4; i++) { /* compute visible quad */ |
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viewloc(ip[i], &vrev, cp[i]); |
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if (ip[i][2] < 0.) |
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return((int)(af + 0.5)); |
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if (ip[i][2] < 0.) { |
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ab = 0; |
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goto finish; |
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} |
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ip[i][0] *= (double)hr; /* scale by resolution */ |
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ip[i][1] *= (double)vr; |
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} |
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(ip[2][0]-ip[0][0])*(ip[1][1]-ip[0][1]); |
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ab += (ip[2][0]-ip[3][0])*(ip[1][1]-ip[3][1]) - |
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(ip[1][0]-ip[3][0])*(ip[2][1]-ip[3][1]); |
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if (ab >= 0) ab *= 0.5; |
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else ab *= -0.5; |
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/* round off smaller area */ |
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if (af <= ab) |
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return((int)(af + 0.5)); |
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return((int)(ab + 0.5)); |
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ab *= ab >= 0 ? 0.5 : -0.5; |
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finish: /* compute penalty based on dist. sightline - viewpoint */ |
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df2 = dist2(vp->vp, pf); |
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db2 = dist2(vp->vp, pb); |
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dfb2 = dist2(pf, pb); |
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penalty = dfb2 + df2 - db2; |
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penalty = df2 - 0.25*penalty*penalty/dfb2; |
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if (df2 > db2) penalty /= df2 <= dfb2 ? sb2 : sb2*df2/dfb2; |
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else penalty /= db2 <= dfb2 ? sf2 : sf2*db2/dfb2; |
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if (penalty < 1.) penalty = 1.; |
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/* round off smaller non-zero area */ |
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if (ab <= FTINY || (af > FTINY && af <= ab)) |
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return((int)(af/penalty + 0.5)); |
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return((int)(ab/penalty + 0.5)); |
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} |
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