osg求交，模型矩阵

Intersector* LineSegmentIntersector::clone(osgUtil::IntersectionVisitor& iv)
{
if (_coordinateFrame==MODEL && iv.getModelMatrix()==0)
{
osg::ref_ptr<LineSegmentIntersector> lsi = new LineSegmentIntersector(_start, _end);
lsi->_parent = this;
return lsi.release();
}

// compute the matrix that takes this Intersector from its CoordinateFrame into the local MODEL coordinate frame
// that geometry in the scene graph will always be in.//
osg::Matrix matrix;
switch (_coordinateFrame)
{
case(WINDOW):
if (iv.getWindowMatrix()) matrix.preMult( *iv.getWindowMatrix() );
if (iv.getProjectionMatrix()) matrix.preMult( *iv.getProjectionMatrix() );
if (iv.getViewMatrix()) matrix.preMult( *iv.getViewMatrix() );
if (iv.getModelMatrix()) matrix.preMult( *iv.getModelMatrix() );
break;
case(PROJECTION):
if (iv.getProjectionMatrix()) matrix.preMult( *iv.getProjectionMatrix() );
if (iv.getViewMatrix()) matrix.preMult( *iv.getViewMatrix() );
if (iv.getModelMatrix()) matrix.preMult( *iv.getModelMatrix() );
break;
case(VIEW):
if (iv.getViewMatrix()) matrix.preMult( *iv.getViewMatrix() );
if (iv.getModelMatrix()) matrix.preMult( *iv.getModelMatrix() );
break;
case(MODEL):
if (iv.getModelMatrix()) matrix = *iv.getModelMatrix();
break;
}

osg::Matrix inverse;
inverse.invert(matrix);

osg::ref_ptr<LineSegmentIntersector> lsi = new LineSegmentIntersector(_start * inverse, _end * inverse);//把相交点转到模型矩阵

//而模型本身不需要转换，其坐标就是在模型坐标系中的坐标,求得的交点也是在局部坐标系中的坐标
lsi->_parent = this;
return lsi.release();

switch(mode)
{
case(GL_TRIANGLES):
{
const Vec3* vlast = &_vertexArrayPtr[first+count]; ///一个geometry下面挂几个drawable,每个drawable下有几个

//primitive，每一个primitive就在此循环一次求交
for(const Vec3* vptr=&_vertexArrayPtr[first];vptr<vlast;vptr+=3)
this->operator()(*(vptr),*(vptr+1),*(vptr+2),_treatVertexDataAsTemporary);
break;
}
case(GL_TRIANGLE_STRIP):
{
const Vec3* vptr = &_vertexArrayPtr[first];
for(GLsizei i=2;i<count;++i,++vptr)
{
if ((i%2)) this->operator()(*(vptr),*(vptr+2),*(vptr+1),_treatVertexDataAsTemporary);
else this->operator()(*(vptr),*(vptr+1),*(vptr+2),_treatVertexDataAsTemporary);
}
break;
}
case(GL_QUADS):
{
const Vec3* vptr = &_vertexArrayPtr[first];
for(GLsizei i=3;i<count;i+=4,vptr+=4)
{
this->operator()(*(vptr),*(vptr+1),*(vptr+2),_treatVertexDataAsTemporary);
this->operator()(*(vptr),*(vptr+2),*(vptr+3),_treatVertexDataAsTemporary);
}
break;
}
case(GL_QUAD_STRIP):
{
const Vec3* vptr = &_vertexArrayPtr[first];
for(GLsizei i=3;i<count;i+=2,vptr+=2)
{
this->operator()(*(vptr),*(vptr+1),*(vptr+2),_treatVertexDataAsTemporary);
this->operator()(*(vptr+1),*(vptr+3),*(vptr+2),_treatVertexDataAsTemporary);
}
break;
}
case(GL_POLYGON): // treat polygons as GL_TRIANGLE_FAN
case(GL_TRIANGLE_FAN):
{
const Vec3* vfirst = &_vertexArrayPtr[first];
const Vec3* vptr = vfirst+1;
for(GLsizei i=2;i<count;++i,++vptr)
{
this->operator()(*(vfirst),*(vptr),*(vptr+1),_treatVertexDataAsTemporary);
}
break;
}
case(GL_POINTS):
case(GL_LINES):
case(GL_LINE_STRIP):
case(GL_LINE_LOOP):
default:
// can't be converted into to triangles.
break;
}
}
}