BezierShape.hpp

Go to the documentation of this file.

//
//  CeresEngine - A game development framework
//
//  Created by Rogiel Sulzbach.
//  Copyright (c) 2018-2022 Rogiel Sulzbach. All rights reserved.
//
 
#pragma once
 
#include "ParametricShape.hpp"
 
#include <algorithm>
#include <limits>
 
namespace CeresEngine::MeshGenerator {
 
    template<int D> class BezierShape {
    private:
        static_assert(D > 1, "D must be > 1.");
 
        using Impl = ParametricShape;
        Impl mParametricShape;
 
        struct ArrayWrapper {
            Vector2 data[D];
 
            ArrayWrapper(const Vector2 (&p)[D]) { std::copy(&p[0], &p[0] + D, &data[0]); }
        };
 
        explicit BezierShape(const ArrayWrapper& p, int segments)
                : mParametricShape{[p](double t) {
                                       ShapeVertex vertex;
 
                                       vertex.position = bezier(p.data, t);
                                       vertex.tangent = bezierDerivative<1>(p.data, t);
 
                                       // If tangent is zero try again near by.
                                       const double e = std::numeric_limits<double>::epsilon();
                                       if(dot(vertex.tangent, vertex.tangent) < e) {
                                           vertex.tangent = bezierDerivative<1>(p.data, t + 10.0 * e);
                                       }
 
                                       vertex.tangent = normalize(vertex.tangent);
                                       vertex.texCoord = t;
 
                                       return vertex;
                                   },
                      segments} {}
 
    public:
        explicit BezierShape(const Vector2 (&p)[D], int segments = 16)
                : // Work around a msvc lambda capture bug by wrapping the array.
                  BezierShape{ArrayWrapper{p}, segments} {}
 
        using Edges = typename Impl::Edges;
        [[nodiscard]] Edges edges() const noexcept { return mParametricShape.edges(); }
 
        using Vertices = typename Impl::Vertices;
        [[nodiscard]] Vertices vertices() const noexcept { return mParametricShape.vertices(); }
    };
 
} // namespace CeresEngine::MeshGenerator