Paul Martz wrote: > > How many first-person rendering systems use the ModelView matrix unmodified? >
The fact that the ModelView matrix is often modified isn't the correct way to look at the problem - we need to consider how the system behaves when it is the identity. Paul Martz wrote: > > How many first-person rendering systems use the ModelView matrix unmodified? > The answer is none, they all set the ModelView matrix to something, and when > app software sets that matrix, the app _must_ make a choice about what _it_ > wants for a coordinate system. The OpenGL default is therefore irrelevant. > An app or SDK can indeed make a choice about which coordinate system to use. However the Y-up OpenGL default is still irrelevant. To illustrate this, consider the OSG implementation of Matrix_implementation::getLookAt(). The code for calculating the up-vector is: Code: up = transform3x3(*this,osg::Vec3d(0.0,1.0,0.0)); which very much relies on the fact that the coordinate system is Y-up. If we pretended that Z-up had equal footing to Y-up then we'd be prone to writing incorrect code such us: Code: up = transform3x3(*this,osg::Vec3d(0.0,0.0,1.0)); Regards, Mik Wells ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=42800#42800 _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
