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e158dab271
Added Saturn and its rings to the raytrace demo. As a side effect of running the unit tests, copyrights got updated for 2022. Happy New Year!
68 lines
2.8 KiB
C++
68 lines
2.8 KiB
C++
/*
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thinring.cpp
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Copyright (C) 2013 by Don Cross - http://cosinekitty.com/raytrace
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the author be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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-------------------------------------------------------------------------
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Implements class ThinRing.
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A thin ring is a disc-shaped surface with zero thickness
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that has a smaller disc-shaped hole at a common center.
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*/
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#include "imager.h"
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namespace Imager
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{
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void ThinRing::ObjectSpace_AppendAllIntersections(
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const Vector& vantage,
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const Vector& direction,
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IntersectionList& intersectionList) const
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{
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if (fabs(direction.z) > EPSILON)
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{
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const double u = -vantage.z / direction.z;
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if (u > EPSILON)
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{
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const double x = u*direction.x + vantage.x;
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const double y = u*direction.y + vantage.y;
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const double m = x*x + y*y;
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if ((m <= r2*r2 + EPSILON) && (r1*r1 <= m + EPSILON))
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{
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Intersection intersection;
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intersection.point = Vector(x, y, 0.0);
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intersection.distanceSquared = (u * direction).MagnitudeSquared();
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// We "cheat" a little bit in calculating the normal vector by knowing too much about the caller.
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// This is necessary because this is not really a normal solid object, but an infinitesimally thin surface.
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// Therefore, we provide a different normal vector depending on the supplied vantage,
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// such that the point of view of the observer determines which side of the surface is seen.
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// (Doing otherwise would cause the surface to appear completely black in some cases.)
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intersection.surfaceNormal = Vector(0.0, 0.0, (vantage.z >= 0.0) ? +1.0 : -1.0);
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intersection.solid = this;
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intersectionList.push_back(intersection);
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}
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}
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}
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}
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}
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