TViewpoint.h

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#pragma once
 
#include "Utility/utility.h"
#include "Utility/traits.h"
 
#include <utility>
#include <type_traits>
 
namespace ph
{
 
enum class EViewpointData
{
    SurfaceHit,
    RasterCoord,
    Radius,
    NumPhotons,
    Tau,
    ViewThroughput,
    ViewDir,
    ViewRadiance
};
 
template<typename T>
concept CViewpoint = std::is_trivially_copyable_v<T> && requires
{
    typename T::PMViewpointTag;
};
 
template<typename Derived>
class TViewpoint
{
public:
    using PMViewpointTag = void;
 
    template<EViewpointData TYPE>
    static constexpr bool has();
 
    template<EViewpointData TYPE>
    decltype(auto) get() const;
 
    template<EViewpointData TYPE, typename T>
    void set(const T& value);
 
// Hide special members as this class is not intended to be used polymorphically.
// It is derived class's choice to expose them (by defining them in public) or not.
protected:
    PH_DEFINE_INLINE_RULE_OF_5_MEMBERS(TViewpoint);
};
 
// In-header Implementations:
 
template<typename Derived>
template<EViewpointData TYPE>
inline constexpr bool TViewpoint<Derived>::has()
{
    static_assert(requires
        {
            { Derived::template impl_has<TYPE>() } -> CSame<bool>;
        },
        "A photon mapping viewpoint type must implement a static method callable as "
        "`impl_has<EViewpointData{}>() -> bool`.");
 
    return Derived::template impl_has<TYPE>();
}
 
template<typename Derived>
template<EViewpointData TYPE>
inline decltype(auto) TViewpoint<Derived>::get() const
{
    static_assert(requires (const Derived derived)
        {
            { derived.template impl_get<TYPE>() } -> CNotSame<void>;
        },
        "A photon mapping viewpoint type must implement a method callable as "
        "`impl_get<EViewpointData{}>() const -> (any type)`.");
 
    return static_cast<const Derived&>(*this).template impl_get<TYPE>();
}
 
template<typename Derived>
template<EViewpointData TYPE, typename T>
inline void TViewpoint<Derived>::set(const T& value)
{
    static_assert(requires (Derived derived, T value)
        {
            { derived.template impl_set<TYPE>(value) } -> CSame<void>;
        },
        "A photon mapping viewpoint type must implement a method callable as "
        "`impl_set<EViewpointData{}, T{}>(T{}) -> void`.");
 
    static_cast<Derived&>(*this).template impl_set<TYPE>(value);
}
 
}// end namespace ph