Hi all, I have a simple question which confuses my mind. While combining transformations (translate/scale/rotation) I create different matrices with Matrix::rotate/scale/translate methods. However, the multiplication order of these single matrices in order to get the final transformation matrix makes difference, I think. This topic have been discussed many times may be, but I have a confusing part I tried to explain below.
OSG Quickstart guide gives the example below: --------------------------- To transform a Vec3 v by a rotation R around a new origin T, use the following code: osg::Matrix T; T.makeTranslate( x, y, z ); osg::Matrix R; R.makeRotate( angle, axis ); Vec3 vPrime = v * R * T; ----------------------------- >From here I understand first translate and then rotate the point. Therefore, premultiplying R with T, processing from right to left. However, OSG 3.0 Beginners Guide says that: --------------------------------------- The order of OSG row-major matrix operations is also easy to understand when concatenating matrices, for example: osg::Matrix mat1 = osg::Matrix::scale(sx, sy, sz); osg::Matrix mat2 = osg::Matrix::translate(x, y, z); osg::Matrix resultMat = mat1 * mat2; Developers can always read the transformation process from left to right, that is, the resultMat means to first scale a vector with mat1, and then translate it with mat2. This explanation always sounds clear and comfortable. --------------------------------------- Is there a difference between these examples or do I confuse the concepts? What is the wrong order/way to combine transformations to use with setMatrix() method? Moreover, OSG transformations always uses local object reference frame or not (instead of global origin (0.0.0) )? For ex: when we rotate a point/object, do we also rotate its local reference frame? In addition to that, does the second rotation use this rotated reference frame (after the first rotation)? Ex: rotate() uses local axis (parameter as Vec3) to rotate around or not? Cheers, Deniz _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
