GteExtremalQuery3.h

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// David Eberly, Geometric Tools, Redmond WA 98052
// Copyright (c) 1998-2017
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt
// http://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
// File Version: 3.0.0 (2016/06/19)

#pragma once

#include <Mathematics/GtePolyhedron3.h>

namespace gte
{

template <typename Real>
class ExtremalQuery3
{
public:
    // Abstract base class.
    virtual ~ExtremalQuery3();

    // Disallow copying and assignment.
    ExtremalQuery3(ExtremalQuery3 const&) = delete;
    ExtremalQuery3& operator=(ExtremalQuery3 const&) = delete;

    // Member access.
    Polyhedron3<Real> const& GetPolytope() const;
    std::vector<Vector3<Real>> const& GetFaceNormals() const;

    // Compute the extreme vertices in the specified direction and return the
    // indices of the vertices in the polyhedron vertex array.
    virtual void GetExtremeVertices(Vector3<Real> const& direction,
        int& positiveDirection, int& negativeDirection) = 0;

protected:
    // The caller must ensure that the input polyhedron is convex.
    ExtremalQuery3(Polyhedron3<Real> const& polytope);

    Polyhedron3<Real> const& mPolytope;
    std::vector<Vector3<Real>> mFaceNormals;
};


template <typename Real>
ExtremalQuery3<Real>::~ExtremalQuery3()
{
}

template <typename Real>
Polyhedron3<Real> const& ExtremalQuery3<Real>::GetPolytope() const
{
    return mPolytope;
}

template <typename Real>
std::vector<Vector3<Real>> const& ExtremalQuery3<Real>::GetFaceNormals() const
{
    return mFaceNormals;
}

template <typename Real>
ExtremalQuery3<Real>::ExtremalQuery3(Polyhedron3<Real> const& polytope)
    :
    mPolytope(polytope)
{
    // Create the face normals.
    auto vertexPool = mPolytope.GetVertices();
    auto const& indices = mPolytope.GetIndices();
    int const numTriangles = static_cast<int>(indices.size()) / 3;
    mFaceNormals.resize(numTriangles);
    for (int t = 0; t < numTriangles; ++t)
    {
        Vector3<Real> v0 = vertexPool[indices[3 * t + 0]];
        Vector3<Real> v1 = vertexPool[indices[3 * t + 1]];
        Vector3<Real> v2 = vertexPool[indices[3 * t + 2]];
        Vector3<Real> edge1 = v1 - v0;
        Vector3<Real> edge2 = v2 - v0;
        mFaceNormals[t] = UnitCross(edge1, edge2);
    }
}

}