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47 lines
1.7 KiB
47 lines
1.7 KiB
// David Eberly, Geometric Tools, Redmond WA 98052
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// Copyright (c) 1998-2021
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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// https://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
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// Version: 4.0.2019.08.13
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#pragma once
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#include <Mathematics/TIQuery.h>
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#include <Mathematics/Cylinder3.h>
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#include <Mathematics/Halfspace.h>
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// Queries for intersection of objects with halfspaces. These are useful for
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// containment testing, object culling, and clipping.
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namespace gte
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{
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template <typename Real>
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class TIQuery<Real, Halfspace3<Real>, Cylinder3<Real>>
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{
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public:
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struct Result
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{
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bool intersect;
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};
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Result operator()(Halfspace3<Real> const& halfspace, Cylinder3<Real> const& cylinder)
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{
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Result result;
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// Compute extremes of signed distance Dot(N,X)-d for points on
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// the cylinder. These are
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// min = (Dot(N,C)-d) - r*sqrt(1-Dot(N,W)^2) - (h/2)*|Dot(N,W)|
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// max = (Dot(N,C)-d) + r*sqrt(1-Dot(N,W)^2) + (h/2)*|Dot(N,W)|
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Real center = Dot(halfspace.normal, cylinder.axis.origin) - halfspace.constant;
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Real absNdW = std::fabs(Dot(halfspace.normal, cylinder.axis.direction));
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Real root = std::sqrt(std::max((Real)1, (Real)1 - absNdW * absNdW));
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Real tmax = center + cylinder.radius * root + (Real)0.5 * cylinder.height * absNdW;
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// The cylinder and halfspace intersect when the projection
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// interval maximum is nonnegative.
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result.intersect = (tmax >= (Real)0);
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return result;
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}
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};
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}
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