differential_geometry.h

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#pragma once

#include <cugar/linalg/vector.h>
#include <cugar/basic/numbers.h>
#include <cugar/spherical/mappings.h>


namespace cugar {

enum SphericalMeasure
{
    kSolidAngle             = 0,
    kProjectedSolidAngle    = 1
};

struct DifferentialGeometry
{
    Vector3f normal_s;      // shading normal
    Vector3f normal_g;      // geometric normal
    Vector3f tangent;       // local tangent
    Vector3f binormal;      // local binormal

    CUGAR_HOST_DEVICE
    Vector3f to_local(const Vector3f v) const
    {
        return Vector3f(
            dot( v, tangent ),
            dot( v, binormal ),
            dot( v, normal_s ) );
    }

    CUGAR_HOST_DEVICE
    Vector3f from_local(const Vector3f v) const
    {
        return
            v.x * tangent +
            v.y * binormal +
            v.z * normal_s;
    }

    CUGAR_HOST_DEVICE
    float cos_theta_l(const Vector3f v) const { return v.z; }

    CUGAR_HOST_DEVICE
    float cos_theta_g(const Vector3f v) const { return dot( v, normal_s ); }
};

} // namespace cugar