http://bugs.freedesktop.org/show_bug.cgi?id=17266
Summary: gl_NormalMatrix definition is wrong
Product: Mesa
Version: CVS
Platform: Other
OS/Version: All
Status: NEW
Severity: normal
Priority: medium
Component: Mesa core
AssignedTo: [email protected]
ReportedBy: [EMAIL PROTECTED]
gl_NormalMatrix, defined at line 84 of slang_builtin.c, in lookup_statevar() is
not defined correctly. The definition:
{ "gl_NormalMatrix", STATE_MODELVIEW_MATRIX, STATE_MATRIX_TRANSPOSE },
is same as for gl_ModelViewMatrix. However, the normal matrix is equal to the
3x3 top-left submatrix of the modelview matrix only if the modelview matrix is
orthogonal (i.e. its columns have length equal to 1.0). If the modelviewmatrix
is not orthogonal (i.e. scaling is applied), this does not hold.
The normal matrix should be computed as the inverse transpose of the top-left
3x3 submatrix of the modelview matrix, as described in section 2.11.3 of the
OpenGL 2.1 specification.
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