basisCurvesTopology.h

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//
// Copyright 2016 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HD_BASIS_CURVES_TOPOLOGY_H
#define PXR_IMAGING_HD_BASIS_CURVES_TOPOLOGY_H

#include "pxr/pxr.h"
#include "pxr/imaging/hd/api.h"
#include "pxr/imaging/hd/version.h"
#include "pxr/imaging/hd/topology.h"
#include "pxr/imaging/hd/tokens.h"

#include "pxr/base/vt/array.h"
#include "pxr/base/vt/value.h"

#include "pxr/base/tf/token.h"

PXR_NAMESPACE_OPEN_SCOPE

/// \class HdBasisCurvesTopology
///
/// Topology data for basisCurves.
///
/// HdBasisCurvesTopology holds the raw input topology data for basisCurves
///
/// The Type, Basis and Wrap mode combined describe the curve and it's
/// segments.
///
/// If Type == linear, the curve is a bunch of line segments and basis is
/// ignored.
///
/// The wrap mode defines how the curve segments are specified:
///
///   If Wrap == segmented, this is equivalent to GL_LINES and curve vertex
///      counts is 2 * number of segments (multiple entries in curve vertex
///      array is optional).
///
///   If Wrap == nonperiodic, this is equivalent to GL_LINE_STRIP and curve
///     counts is an array where each entry is the number of vertices in that
///     line segment.  The first and last vertex in the segment are not joined.
///
///   If Wrap == periodic, this is equivalent to GL_LINE_LOOP  and curve counts
///     is an array where each entry is the number of vertices in that line
///     segment. An additional line is place between the first and last vertex
///     in each segment.
///
///  If Type == cubic, the type of curve is specified by basis:
///     The Basis can be bezier, bspline, catmullRom, or centripetalCatmullRom.
///
///     Wrap can be either periodic or nonperiodic (segmented is unsupported).
///
///  For each type of line, the generated vertex indices can pass through an
///  optional index buffer to map the generated indices to actual indices in
///  the vertex buffer.
///
class HdBasisCurvesTopology : public HdTopology {
public:

    HD_API
    HdBasisCurvesTopology();
    HD_API
    HdBasisCurvesTopology(const HdBasisCurvesTopology &src);

    HD_API
    HdBasisCurvesTopology(const TfToken &curveType,
                          const TfToken &curveBasis,
                          const TfToken &curveWrap,
                          const VtIntArray &curveVertexCounts,
                          const VtIntArray &curveIndices);
    HD_API
    virtual ~HdBasisCurvesTopology();

    ///
    /// \name Topological invisibility
    /// @{
    ///
    HD_API
    void SetInvisiblePoints(VtIntArray const &invisiblePoints) {
        _invisiblePoints = invisiblePoints;
    }

    HD_API
    VtIntArray const & GetInvisiblePoints() const {
        return _invisiblePoints;
    }

    HD_API
    void SetInvisibleCurves(VtIntArray const &invisibleCurves) {
        _invisibleCurves = invisibleCurves;
    }

    HD_API
    VtIntArray const & GetInvisibleCurves() const {
        return _invisibleCurves;
    }
    /// @}

    /// Returns segment vertex counts.
    VtIntArray const &GetCurveVertexCounts() const {
        return _curveVertexCounts;
    }

    /// Returns indices.
    VtIntArray const &GetCurveIndices() const {
        return _curveIndices;
    }

    /// Returns the number of curves
    size_t GetNumCurves() const {
        return _curveVertexCounts.size();
    }

    /// Returns the number of points implied by vertex counts and indices
    HD_API
    size_t GetNumPoints() const {
        return _numPoints;
    }

    /// See class documentation for valid combination of values
    TfToken GetCurveType() const { return _curveType; }
    TfToken GetCurveBasis() const { return _curveBasis; }
    TfToken GetCurveWrap() const { return _curveWrap; }

    /// Does the topology use an index buffer
    bool HasIndices() const { return !_curveIndices.empty(); }

    /// Returns the hash value of this topology to be used for instancing.
    HD_API
    virtual ID ComputeHash() const;

    /// Equality check between two basisCurves topologies.
    HD_API
    bool operator==(HdBasisCurvesTopology const &other) const;
    HD_API
    bool operator!=(HdBasisCurvesTopology const &other) const;

    /// Figure out how many vertices / control points this topology references
    HD_API
    size_t CalculateNeededNumberOfControlPoints() const;

    /// Figure out how many control points with varying data this topology needs
    HD_API
    size_t CalculateNeededNumberOfVaryingControlPoints() const;

private:
    TfToken _curveType;
    TfToken _curveBasis;
    TfToken _curveWrap;
    VtIntArray _curveVertexCounts;
    VtIntArray _curveIndices;
    VtIntArray _invisiblePoints;
    VtIntArray _invisibleCurves;
    size_t _numPoints;
};

HD_API
std::ostream& operator << (std::ostream &out, HdBasisCurvesTopology const &topo);


PXR_NAMESPACE_CLOSE_SCOPE

#endif // PXR_IMAGING_HD_BASIS_CURVES_TOPOLOGY_H