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Timestamp:
09/17/08 18:14:28 (6 years ago)
Author:
robert
Message:

From Mathias Froehlich, "This is a generic optimization that does not depend on any cpu or instruction
set.

The optimization is based on the observation that matrix matrix multiplication
with a dense matrix 4x4 is 43 Operations whereas multiplication with a
transform, or scale matrix is only 4
2 operations. Which is a gain of a
*FACTOR*4* for these special cases.
The change implements these special cases, provides a unit test for these
implementation and converts uses of the expensiver dense matrix matrix
routine with the specialized versions.

Depending on the transform nodes in the scenegraph this change gives a
noticable improovement.
For example the osgforest code using the MatrixTransform? is about 20% slower
than the same codepath using the PositionAttitudeTransform? instead of the
MatrixTransform? with this patch applied.

If I remember right, the sse type optimizations did *not* provide a factor 4
improovement. Also these changes are totally independent of any cpu or
instruction set architecture. So I would prefer to have this current kind of
change instead of some hand coded and cpu dependent assembly stuff. If we
need that hand tuned stuff, these can go on top of this changes which must
provide than hand optimized additional variants for the specialized versions
to give a even better result in the end.

An other change included here is a change to rotation matrix from quaterion
code. There is a sqrt call which couold be optimized away. Since we divide in
effect by sqrt(length)*sqrt(length) which is just length ...
"

Files:
1 modified

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  • OpenSceneGraph/trunk/examples/osgdepthpeeling/osgdepthpeeling.cpp

    r7648 r8868  
    175175  void rotate(float x, float y) 
    176176  { 
    177     osg::Matrixd baseMatrix = _modelGroupTransform->getMatrix(); 
    178      
    179     osg::Matrixd preTransMatrix; 
    180     osg::Matrixd postTransMatrix; 
    181     osg::Matrixd rotMatrixX; 
    182     osg::Matrixd rotMatrixZ; 
    183      
    184     preTransMatrix.makeTranslate(_rotCenter); 
    185     postTransMatrix.makeTranslate(-_rotCenter); 
    186  
    187     rotMatrixZ.makeRotate((x - _prevX) * 3., osg::Vec3d(0.0, 0.0,1.0)); 
    188      
    189     baseMatrix.preMult(preTransMatrix); 
    190     baseMatrix.preMult(rotMatrixZ); 
    191     baseMatrix.preMult(postTransMatrix); 
    192  
    193     rotMatrixX.makeRotate(-(y - _prevY) * 3., (baseMatrix * osg::Vec3d(1.0, 0.0,0.0))); 
    194      
    195     baseMatrix.preMult(preTransMatrix); 
    196     baseMatrix.preMult(rotMatrixX); 
    197     baseMatrix.preMult(postTransMatrix); 
     177    osg::Matrix baseMatrix = _modelGroupTransform->getMatrix(); 
     178     
     179    baseMatrix.preMultTranslate(_rotCenter); 
     180    baseMatrix.preMultRotate(osg::Quat((x - _prevX) * 3, osg::Vec3d(0.0, 0.0, 1.0))); 
     181    baseMatrix.preMultRotate(osg::Quat(-(y - _prevY) * 3, (baseMatrix * osg::Vec3d(1.0, 0.0, 0.0)))); 
     182    baseMatrix.preMultTranslate(-_rotCenter); 
    198183     
    199184    _modelGroupTransform->setMatrix(baseMatrix);