OpenSubdiv/opensubdiv/far/gregoryBasis.h

//
//   Copyright 2013 Pixar
//
//   Licensed under the Apache License, Version 2.0 (the "Apache License")
//   with the following modification; you may not use this file except in
//   compliance with the Apache License and the following modification to it:
//   Section 6. Trademarks. is deleted and replaced with:
//
//   6. Trademarks. This License does not grant permission to use the trade
//      names, trademarks, service marks, or product names of the Licensor
//      and its affiliates, except as required to comply with Section 4(c) of
//      the License and to reproduce the content of the NOTICE file.
//
//   You may obtain a copy of the Apache License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the Apache License with the above modification is
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#ifndef OPENSUBDIV3_FAR_GREGORY_BASIS_H
#define OPENSUBDIV3_FAR_GREGORY_BASIS_H

#include "../vtr/level.h"
#include "../vtr/stackBuffer.h"
#include "../far/types.h"
#include "../far/stencilTable.h"
#include <cstring>

namespace OpenSubdiv {
namespace OPENSUBDIV_VERSION {

namespace Far {

class TopologyRefiner;

/// \brief Container for utilities relating to Gregory patch construction
///
/// The GregoryBasis class has been reduced to a simple container of subclasses and
/// utilities (static methods) used by the EndCap Factories.  It remains a class as
/// its methods to support stencil construction currently require it to be a friend
/// of the StencilTable class.
///
class GregoryBasis {
public:
    //
    // Basis point
    //
    // Implements arithmetic operators to manipulate the influence of the
    // 1-ring control vertices supporting the patch basis
    //
    class Point {
    public:
        // 40 means up to valence=10 is on stack
        static const int RESERVED_STENCIL_SIZE = 40;

        Point(int stencilCapacity=RESERVED_STENCIL_SIZE) : _size(0) {
            _stencils.SetSize(stencilCapacity);
        }

        Point(Point const & other) {
            _stencils.SetSize(other._stencils.GetSize());
            *this = other;
        }

        int GetSize() const {
            return _size;
        }

        int GetCapacity() const {
            return _stencils.GetSize();
        }

        void Clear(int capacity) {
            _size = 0;
            if ((int)_stencils.GetSize() < capacity) {
                _stencils.SetSize(capacity);
            }
        }

        void AddWithWeight(Vtr::Index idx, float weight) {
            for (int i = 0; i < _size; ++i) {
                if (_stencils[i].index == idx) {
                    _stencils[i].weight += weight;
                    return;
                }
            }
            assert(_size < (int)_stencils.GetSize());
            _stencils[_size].index = idx;
            _stencils[_size].weight = weight;
            ++_size;
        }

        void AddWithWeight(Point const &src, float weight) {
            for (int i = 0; i < src._size; ++i) {
                AddWithWeight(src._stencils[i].index,
                              src._stencils[i].weight * weight);
            }
        }

        Point & operator = (Point const & other) {
            Clear(other.GetCapacity());
            _size = other._size;
            assert(_size <= (int)_stencils.GetSize());
            for (int i = 0; i < _size; ++i) {
                _stencils[i] = other._stencils[i];
            }
            return *this;
        }

        Point & operator *= (float f) {
            for (int i=0; i<_size; ++i) {
                _stencils[i].weight *= f;
            }
            return *this;
        }

        void OffsetIndices(Vtr::Index offset) {
            for (int i=0; i<_size; ++i) {
                _stencils[i].index += offset;
            }
        }

        void Copy(int ** size, Vtr::Index ** indices, float ** weights) const {
            for (int i = 0; i < _size; ++i) {
                **indices = _stencils[i].index;
                **weights = _stencils[i].weight;
                ++(*indices);
                ++(*weights);
            }
            **size = _size;
            ++(*size);
        }

        Vtr::Index GetStencilIndex(int index) const {
            return _stencils[index].index;
        }
        float GetStencilWeight(int index) const {
            return _stencils[index].weight;
        }

    private:
        int _size;

        struct Stencil {
            Vtr::Index index;
            float weight;
        };

        Vtr::internal::StackBuffer<Stencil, RESERVED_STENCIL_SIZE> _stencils;
    };

    //
    // ProtoBasis
    //
    // Given a Vtr::Level and a face index, gathers all the influences of the
    // 1-ring that supports the 20 CVs of a Gregory patch basis.
    //
    struct ProtoBasis {

        ProtoBasis(Vtr::internal::Level const & level,
                   Vtr::Index faceIndex,
                   Vtr::internal::Level::VSpan const cornerSpans[],
                   int levelVertOffset,
                   int fvarChannel);

        // Control Vertices based on :
        // "Approximating Subdivision Surfaces with Gregory Patches for Hardware
        // Tessellation" Loop, Schaefer, Ni, Castano (ACM ToG Siggraph Asia
        // 2009)
        //
        //  P3         e3-      e2+         P2
        //     O--------O--------O--------O
        //     |        |        |        |
        //     |        |        |        |
        //     |        | f3-    | f2+    |
        //     |        O        O        |
        // e3+ O------O            O------O e2-
        //     |     f3+          f2-     |
        //     |                          |
        //     |                          |
        //     |      f0-         f1+     |
        // e0- O------O            O------O e1+
        //     |        O        O        |
        //     |        | f0+    | f1-    |
        //     |        |        |        |
        //     |        |        |        |
        //     O--------O--------O--------O
        //  P0         e0+      e1-         P1
        //

        Point P[4], Ep[4], Em[4], Fp[4], Fm[4];

        // for varying interpolation
        Vtr::Index varyingIndex[4];
    };

    // for basis point stencil
    static void AppendToStencilTable(GregoryBasis::Point const &p,
                                     StencilTable *table) {
        int size = p.GetSize();
        table->_sizes.push_back(size);
        for (int i = 0; i < size; ++i) {
            table->_indices.push_back(p.GetStencilIndex(i));
            table->_weights.push_back(p.GetStencilWeight(i));
        }
    }

    // for varying stencil (just copy)
    static void AppendToStencilTable(int index, StencilTable *table) {
        table->_sizes.push_back(1);
        table->_indices.push_back(index);
        table->_weights.push_back(1.f);
    }
};

} // end namespace Far

} // end namespace OPENSUBDIV_VERSION
} // end namespace OpenSubdiv

#endif /* OPENSUBDIV3_FAR_GREGORY_BASIS_H */