RixShadingBuiltin.h

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#ifndef RixBuiltinShading_h
#define RixBuiltinShading_h

#include <cstddef>                      // for NULL
#include "RixBxdf.h"                    // for RixBXTransportTrait, etc
#include "RixBxdfLobe.h"                // for RixBXLobeWeights (ptr only), etc
#include "RixShading.h"                 // for RixSCDetail, etc
#include "RiTypesHelper.h"              // for RtVector3, etc

class RixIntegratorContext;
class RixLightingServices;
class RixRNG;
struct RtRayGeometry;

// Subsurface scattering using diffusion approximations:
// Burley normalized or three-lobe parameterization
class RixSSDiffusion : public RixVolumeIntegrator
{
public:
    RixSSDiffusion(
        RixShadingContext const* sCtx,
        RixBxdfFactory* f,
        void* _instanceData)
        : RixVolumeIntegrator(sCtx, f, _instanceData)
    {
    }
    struct Params
    {
        Params()
            : _version(5),
              dmfp(NULL),
              mfp(NULL),
              bumpNormal(NULL),
              continuationRays(0),
              followTopology(NULL),
              flipSssHitVn(false)
        {
        }

        int const _version; // always first in the struct

        // Parameterization #1 (used by e.g. LamaSSS):
        // (only set one of *dmfp or *mfp; set the other one to NULL)
        RtColorRGB const* albedo;
        RixSCDetail albedoDetail; // is albedo uniform or varying?
        RtColorRGB const* dmfp;   // rgb diffuse mean free path lengths
        RixSCDetail dmfpDetail;   // is dmfp uniform or varying?
        RtColorRGB const* mfp;    // rgb mean free path -- alternative to dmfp
        RixSCDetail mfpDetail;    // is mfp uniform or varying?

        // Parameterization #2 (used by e.g. LamaTricolorSSS):
        RtColorRGB const *color1, *color2, *color3; // 3 colors
        RixSCDetail color1Detail, color2Detail, color3Detail;
        float const *weight1, *weight2, *weight3; // 3 weights
        RixSCDetail weight1Detail, weight2Detail, weight3Detail;
        float const *dmfp1, *dmfp2, *dmfp3; // 3 diff. mean free path lengths
        RixSCDetail dmfp1Detail, dmfp2Detail, dmfp3Detail;

        float unitLength;

        RtVector3 const* bumpNormal; // for bump-mapped normals

        int continuationRays; // shoot sss continuation rays?

        float const* followTopology; // decrease sss in concave regions?  (was uniform before RenderMan 25)

        bool flipSssHitVn;  // flip Vn direction at sss ray hit points (not diffusesss approx shading pts)

        // future parameters will appear here.

        char _reserved[32]; // always last in the struct
    };
    virtual void GetNearestHits(
        int nRays,
        RtRayGeometry const* rays,
        RixRNG* rng,
        RixBXLobeTraits const& lobesWanted,
        RixIntegratorContext& iCtx,
        RixLightingServices* lightingServices,
        IntegratorDelegate* lcb,
        int* numShadingCtxs,
        RixShadingContext const** shadingCtxs,
        RtUString const subset        = US_NULL,
        RtUString const excludeSubset = US_NULL,
        bool isLightPath          = false,
        RtHitSides hitSides       = k_SidesBoth,
        bool isPrimary            = false) = 0;

protected:
    virtual ~RixSSDiffusion() {}
};

// Subsurface scattering as brute-force volume scattering
class RixSSPathTraced : public RixVolumeIntegrator
{
public:
    RixSSPathTraced(
        RixShadingContext const* sCtx,
        RixBxdfFactory* f,
        void* _instanceData)
        : RixVolumeIntegrator(sCtx, f, _instanceData)
    {
    }
    struct Params
    {
        Params()
            : _version(1),
              dmfp(NULL),
              bumpNormal(NULL)
        {
        }

        int const _version; // always first in the struct

        // Main parameters: albedo, dmfp, ior, g
        RtColorRGB const* albedo;
        RixSCDetail albedoDetail; // is albedo uniform or varying?
        RtColorRGB const* dmfp;   // rgb diffuse mean free path lengths
        RixSCDetail dmfpDetail;   // is dmfp uniform or varying?
        float const* ior;         // index of refraction
        RixSCDetail iorDetail;    // is ior uniform or varying?
        float const* g;           // scattering mean cosine (anisotropy)
        RixSCDetail gDetail;      // is g uniform or varying?

        // Additional parameters:
        float diffuseSwitch;      // distance for switch between diffuse and sss (ignored: not used for ptsss)
        float bias;
        int disableAlbedoInversion;  // (obsolete or debug only?)
        RtUString subset;
        bool resolveSelfIntersections;
        float internalReflectionsEta;
        float unitLength;         // multiplier on dmfp values

        RtVector3 const* bumpNormal; // for bump-mapped normals

        // future parameters will appear here.

        char _reserved[32]; // always last in the struct
    };
    virtual void GetNearestHits(
        int nRays,
        RtRayGeometry const* rays,
        RixRNG* rng,
        RixBXLobeTraits const& lobesWanted,
        RixIntegratorContext& iCtx,
        RixLightingServices* lightingServices,
        IntegratorDelegate* lcb,
        int* numShadingCtxs,
        RixShadingContext const** shadingCtxs,
        RtUString const subset        = US_NULL,
        RtUString const excludeSubset = US_NULL,
        bool isLightPath          = false,
        RtHitSides hitSides       = k_SidesBoth,
        bool isPrimary            = false) = 0;

protected:
    virtual ~RixSSPathTraced() {}
};

class RixNullBxdf : public RixBxdf
{
public:
    virtual RixBXEvaluateDomain GetEvaluateDomain() = 0;
    virtual void GetAllLobeTraits(RixBXLobeTraits*) = 0;
    virtual int GetNumLobes() = 0;

    virtual void GenerateSample(
        RixBXTransportTrait transportTrait,
        RixBXLobeTraits const* lobesWanted,
        RixRNG* rng,
        RixBXLobeSampled* lobeSampled,
        RtVector3* directions,
        RixBXLobeWeights& weights,
        float* forwardPdfs,
        float* reversePdfs,
        RtColorRGB* compTrans = NULL) = 0;

    virtual void EvaluateSample(
        RixBXTransportTrait transportTrait,
        RixBXLobeTraits const* lobesWanted,
        RixRNG* rng,
        RixBXLobeTraits* lobesEvaluated,
        RtVector3 const* directions,
        RixBXLobeWeights& weights,
        float* forwardPdfs,
        float* reversePdfs) = 0;

    virtual void EvaluateSamplesAtIndex(
        RixBXTransportTrait transportTrait,
        RixBXLobeTraits const& lobesWanted,
        RixRNG* rng,
        int index,
        int nSamples,
        RixBXLobeTraits* lobesEvaluated,
        RtVector3 const* directions,
        RixBXLobeWeights& weights,
        float* forwardPdfs,
        float* reversePdfs) = 0;

private:
    // no parameters..
    virtual ~RixNullBxdf() {}
};

// RixLambertBxdf and RixDirac may go here...

#endif