OpenSubdiv/opensubdiv/far/patchMap.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:
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//
//   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.
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//   You may obtain a copy of the Apache License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
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//   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_PATCH_MAP_H
#define OPENSUBDIV3_FAR_PATCH_MAP_H

#include "../version.h"

#include "../far/patchTable.h"

#include <cassert>

namespace OpenSubdiv {
namespace OPENSUBDIV_VERSION {

namespace Far {

/// \brief An quadtree-based map connecting coarse faces to their sub-patches
///
/// PatchTable::PatchArrays contain lists of patches that represent the limit
/// surface of a mesh, sorted by their topological type. These arrays break the
/// connection between coarse faces and their sub-patches.
///
/// The PatchMap provides a quad-tree based lookup structure that, given a singular
/// parametric location, can efficiently return a handle to the sub-patch that
/// contains this location.
///
class PatchMap {
public:

    typedef PatchTable::PatchHandle Handle;

    /// \brief Constructor
    ///
    /// @param patchTable  A valid set of PatchTable
    ///
    PatchMap( PatchTable const & patchTable );

    /// \brief Returns a handle to the sub-patch of the face at the given (u,v).
    /// Note : the faceid corresponds to quadrangulated face indices (ie. quads
    /// count as 1 index, non-quads add as many indices as they have vertices)
    ///
    /// @param faceid  The index of the face
    ///
    /// @param u       Local u parameter
    ///
    /// @param v       Local v parameter
    ///
    /// @return        A patch handle or NULL if the face does not exist or the
    ///                limit surface is tagged as a hole at the given location
    ///
    Handle const * FindPatch( int faceid, float u, float v ) const;

private:

    inline void initialize( PatchTable const & patchTable );

    // Quadtree node with 4 children
    struct QuadNode {
        struct Child {
            unsigned int isSet:1,    // true if the child has been set
                         isLeaf:1,   // true if the child is a QuadNode
                         idx:30;     // child index (either QuadNode or Handle)
        };

        // sets all the children to point to the patch of index patchIdx
        void SetChild(int patchIdx);

        // sets the child in "quadrant" to point to the node or patch of the given index
        void SetChild(unsigned char quadrant, int child, bool isLeaf=true);

        Child children[4];
    };

    typedef std::vector<QuadNode> QuadTree;

    // adds a child to a parent node and pushes it back on the tree
    static QuadNode * addChild( QuadTree & quadtree, QuadNode * parent, int quadrant );

    // given a median, transforms the (u,v) to the quadrant they point to, and
    // return the quadrant index.
    //
    // Quadrants indexing:
    //
    //   (0,0) o-----o-----o
    //         |     |     |
    //         |  0  |  3  |
    //         |     |     |
    //         o-----o-----o
    //         |     |     |
    //         |  1  |  2  |
    //         |     |     |
    //         o-----o-----o (1,1)
    //
    template <class T> static int resolveQuadrant(T & median, T & u, T & v);

    std::vector<Handle>   _handles;  // all the patches in the PatchTable
    std::vector<QuadNode> _quadtree; // quadtree nodes
};

// given a median, transforms the (u,v) to the quadrant they point to, and
// return the quadrant index.
template <class T> int
PatchMap::resolveQuadrant(T & median, T & u, T & v) {
    int quadrant = -1;

    if (u<median) {
        if (v<median) {
            quadrant = 0;
        } else {
            quadrant = 1;
            v-=median;
        }
    } else {
        if (v<median) {
            quadrant = 3;
        } else {
            quadrant = 2;
            v-=median;
        }
        u-=median;
    }
    return quadrant;
}

/// Returns a handle to the sub-patch of the face at the given (u,v).
inline PatchMap::Handle const *
PatchMap::FindPatch( int faceid, float u, float v ) const {

    if (faceid>=(int)_quadtree.size())
        return NULL;

    assert( (u>=0.0f) && (u<=1.0f) && (v>=0.0f) && (v<=1.0f) );

    QuadNode const * node = &_quadtree[faceid];

    float half = 0.5f;

    // 0xFF : we should never have depths greater than k_InfinitelySharp
    for (int depth=0; depth<0xFF; ++depth) {

        float delta = half * 0.5f;

        int quadrant = resolveQuadrant( half, u, v );
        assert(quadrant>=0);

        // is the quadrant a hole ?
        if (! node->children[quadrant].isSet)
            return 0;

        if (node->children[quadrant].isLeaf) {
            return &_handles[node->children[quadrant].idx];
        } else {
            node = &_quadtree[node->children[quadrant].idx];
        }

        half = delta;
    }

    assert(0);
    return 0;
}

} // end namespace Far

} // end namespace OPENSUBDIV_VERSION
using namespace OPENSUBDIV_VERSION;

} // end namespace OpenSubdiv

#endif /* OPENSUBDIV3_FAR_PATCH_PARAM */