CSegmentArray.h

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//==============================================================================
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    \author    <http://www.chai3d.org>
    \author    Francois Conti
    \version   3.2.0 $Rev: 2015 $
*/
//==============================================================================

//------------------------------------------------------------------------------
#ifndef CSegmentArrayH
#define CSegmentArrayH
//------------------------------------------------------------------------------
#include "graphics/CGenericArray.h"
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
namespace chai3d {
//------------------------------------------------------------------------------

//==============================================================================
//==============================================================================

//------------------------------------------------------------------------------
class cSegmentArray;
typedef std::shared_ptr<cSegmentArray> cSegmentArrayPtr;
//------------------------------------------------------------------------------

//==============================================================================
//==============================================================================
class cSegmentArray : public cGenericArray
{
    //--------------------------------------------------------------------------
    // CONSTRUCTOR & DESTRUCTOR:
    //--------------------------------------------------------------------------

public:

    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    cSegmentArray(cVertexArrayPtr a_vertexArray) : cGenericArray(a_vertexArray)
    {
        // clear all segments
        clear();

        // store pointer to vertex array
        m_vertices = a_vertexArray;

        // initialize OpenGL buffer ID 
        m_elementBuffer         = 0;
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    ~cSegmentArray(){}


    void clear()
    {
        m_allocated.clear();
        m_indices.clear();
        m_freeElements.clear();
        m_flagMarkForUpdate     = true;
        m_flagMarkForResize     = true;
    }


    static cSegmentArrayPtr create(cVertexArrayPtr a_vertexArray) { return (std::make_shared<cSegmentArray>(a_vertexArray)); }


    //--------------------------------------------------------------------------
    // PUBLIC METHODS:
    //--------------------------------------------------------------------------

public:

    virtual unsigned int getNumVerticesPerElement() { return (2); }

    cSegmentArrayPtr copy();

    void compress();


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    int newSegment(const unsigned int a_vertexIndex0,
                   const unsigned int a_vertexIndex1)
    {
        int index;

        // check if there is an available slot on the free segment list
        if (m_freeElements.size() > 0)
        {
            index = m_freeElements.front();
            m_allocated[index] = true;
            m_freeElements.pop_front();
            setVertices(index, a_vertexIndex0, a_vertexIndex1);
        }
        else
        {
            // store new indices
            m_indices.push_back(a_vertexIndex0);
            m_indices.push_back(a_vertexIndex1);
            m_allocated.push_back(true);

            m_flagMarkForResize = true;

            // store index of new segment
            index = (int)(m_allocated.size())-1;
        }

        // mark for update
        m_flagMarkForUpdate = true;

        // return index to new segment
        return (index);
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    void removeSegment(const unsigned int a_segmentIndex)
    {
        // sanity check
        if (m_allocated[a_segmentIndex])
        {
            // disable segment
            m_allocated[a_segmentIndex] = false;

            // reset indices to vertices
            setVertices(a_segmentIndex, 0, 0);

            // add segment to free list
            m_freeElements.push_back(a_segmentIndex);

            // mark for update
            m_flagMarkForUpdate = true;
        }
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    inline void setVertices(const unsigned int a_segmentIndex,
                            const unsigned int a_vertexIndex0,
                            const unsigned int a_vertexIndex1)
    {
        m_indices[2*a_segmentIndex+0] = a_vertexIndex0;
        m_indices[2*a_segmentIndex+1] = a_vertexIndex1;

        // mark for update
        m_flagMarkForUpdate = true;
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    inline unsigned int getVertexIndex0(const unsigned int a_segmentIndex) const
    {
        return (m_indices[2*a_segmentIndex+0]);
    };


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    inline unsigned int getVertexIndex1(const unsigned int a_segmentIndex) const
    {
        return (m_indices[2*a_segmentIndex+1]);
    };


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    virtual unsigned int getVertexIndex(const unsigned int a_elementIndex,
                                        const unsigned int a_vertexNumber) const
    {
        switch (a_vertexNumber)
        {
            case 0: return (m_indices[2*a_elementIndex+0]);
            case 1: return (m_indices[2*a_elementIndex+1]);
            default: return (0);
        }
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    cVector3d getTexCoordAtPosition(const unsigned int a_segmentIndex, 
                                    const cVector3d& a_localPos)
    {
        // get vertices of contact segments
        cVector3d vertex0 = m_vertices->getLocalPos(getVertexIndex0(a_segmentIndex));
        cVector3d vertex1 = m_vertices->getLocalPos(getVertexIndex1(a_segmentIndex));

        // project desired point on segment
        cVector3d point = cProjectPointOnSegment(a_localPos, vertex0, vertex1);

        // compute weights based on position of contact point
        double c0, c1;

        double distance01 = cDistance(vertex0, vertex1);
        if (distance01 < C_SMALL)
        {
            c0 = 1.0;
            c1 = 0.0;
        }
        else
        {
            double distanceP0 = cDistance(vertex0, point);
            c1 = distanceP0 / distance01;
            c0 = 1.0 - c1;
        }

        cVector3d texCoord;

        if (m_vertices->getUseTexCoordData())
        {
            // retrieve the texture coordinate for each segment vertex
            cVector3d texCoord0 = m_vertices->getTexCoord(getVertexIndex0(a_segmentIndex));
            cVector3d texCoord1 = m_vertices->getTexCoord(getVertexIndex1(a_segmentIndex));

            // compute the exact texture coordinate at the contact point
            texCoord = cAdd( cMul(c0, texCoord0), cMul(c1, texCoord1));
        }
        else
        {
            texCoord.set(0.0, 0.0, 0.0);
        }

        // return result
        return (texCoord);
    }


    //--------------------------------------------------------------------------
    //--------------------------------------------------------------------------
    inline void render()
    { 
#ifdef C_USE_OPENGL
        unsigned int numSegments = getNumElements();

        // allocate object and buffers if needed
        if (m_elementBuffer == 0)
        {
            glGenBuffers(1, &m_elementBuffer);
        }

        // bind buffer
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_elementBuffer);

        // update buffer size if needed
        if (m_flagMarkForResize)
        {
            glBufferData(GL_ELEMENT_ARRAY_BUFFER, 2 * numSegments * sizeof(unsigned int), &(m_indices[0]), GL_STATIC_DRAW);
            m_flagMarkForResize = true;
        }

        // update data if needed
        if (m_flagMarkForUpdate)
        {
            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_elementBuffer);
            glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, 2 * numSegments * sizeof(unsigned int), &(m_indices[0]));

            m_flagMarkForUpdate = false;
        }

        // render object
        m_vertices->renderInitialize();
        
        glEnableClientState(GL_VERTEX_ARRAY);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_elementBuffer);
        glDrawElements( GL_LINES, 2 * numSegments, GL_UNSIGNED_INT, (void*)0);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

         m_vertices->renderFinalize();
#endif
    }

    virtual bool computeCollision(const unsigned int a_elementIndex,
                                  cGenericObject* a_object,
                                  cVector3d& a_segmentPointA,
                                  cVector3d& a_segmentPointB,
                                  cCollisionRecorder& a_recorder,
                                  cCollisionSettings& a_settings) const;
};

//------------------------------------------------------------------------------
} // namespace chai3d
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
#endif
//------------------------------------------------------------------------------