tangent.h

/*****************************************************************************
 * VCLib                                                                     *
 * Visual Computing Library                                                  *
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 * Copyright(C) 2021-2025                                                    *
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#ifndef VCL_MESH_COMPONENTS_TANGENT_H
#define VCL_MESH_COMPONENTS_TANGENT_H
 
#include "base/component.h"
#include "base/predicates.h"
 
#include <vclib/mesh/elements/base/base.h>
#include <vclib/mesh/exceptions.h>
 
#include <vclib/base.h>
#include <vclib/space/core.h>
 
namespace vcl::comp {
 
template<PointConcept P, typename ParentElemType = void, bool OPT = false>
class Tangent :
        public Component<
            Tangent<P, ParentElemType, OPT>,
            CompId::TANGENT,
            std::pair<P, bool>,
            ParentElemType,
            !std::is_same_v<ParentElemType, void>,
            OPT>
{
    using Base = Component<
        Tangent<P, ParentElemType, OPT>,
        CompId::TANGENT,
        std::pair<P, bool>,
        ParentElemType,
        !std::is_same_v<ParentElemType, void>,
        OPT>;
 
public:
    using TangentType = P;
 
    /* Constructors */
 
    Tangent()
    {
        if constexpr (!Base::IS_VERTICAL) {
            init();
        }
    }
 
    void init() { Base::data().second = true; }
 
    /* Member functions */
 
    const P& tangent() const { return Base::data().first; }
 
    P& tangent() { return Base::data().first; }
 
    bool tangentRightHanded() const { return Base::data().second; }
 
    bool& tangentRightHanded() { return Base::data().second; }
 
    P bitangent() const
    {
        const ParentElemType& parent =
            static_cast<const ParentElemType&>(*this);
 
        if (isComponentAvailableOn<CompId::NORMAL>(parent)) {
            // compute bitangent using the tangent and normal
            // assuming that normal is available
            const auto& n = static_cast<const ParentElemType&>(*this).normal();
            return tangentRightHanded() ? n.cross(tangent()) :
                                          tangent().cross(n);
        }
        else {
            throw MissingComponentException(
                "Per " +
                std::string(elementEnumString<ParentElemType::ELEMENT_ID>()) +
                " Normal Component is not enabled.");
            return P();
        }
    }
 
protected:
    // Component interface functions
    template<typename Element>
    void importFrom(const Element& e, bool = true);
 
    void serialize(std::ostream& os) const
    {
        tangent().serialize(os);
        vcl::serialize(os, tangentRightHanded());
    }
 
    void deserialize(std::istream& is)
    {
        tangent().deserialize(is);
        vcl::deserialize(is, tangentRightHanded());
    }
};
 
/* concepts */
 
template<typename T>
concept HasTangent = TTB::IsDerivedFromSpecializationOfV<T, Tangent>;
 
template<typename T>
concept HasOptionalTangent =
    HasTangent<T> && IsOptionalComponent<typename RemoveRef<T>::Tangent>;
 
/* importFrom function */
 
template<PointConcept P, typename ParentElemType, bool OPT>
template<typename Element>
void Tangent<P, ParentElemType, OPT>::importFrom(const Element& e, bool)
{
    using ScalarType = TangentType::ScalarType;
    if constexpr (HasTangent<Element>) {
        if (isTangentAvailableOn(e)) {
            tangent()            = e.tangent().template cast<ScalarType>();
            tangentRightHanded() = e.tangentRightHanded();
        }
    }
}
 
/* Detector function to check if a class has Tangent available */
 
bool isTangentAvailableOn(const auto& element)
{
    return isComponentAvailableOn<CompId::TANGENT>(element);
}
 
/* Specialization Aliases */
 
template<typename Scalar, typename ElementType = void, bool OPT = false>
using Tangent3 = Tangent<Point3<Scalar>, ElementType, OPT>;
 
template<typename ElementType = void, bool OPT = false>
using Tangent3f = Tangent3<float, ElementType, OPT>;
 
template<typename ElementType = void, bool OPT = false>
using Tangent3d = Tangent3<double, ElementType, OPT>;
 
} // namespace vcl::comp
 
#endif // VCL_MESH_COMPONENTS_TANGENT_H