The RenderMan Interface - Paul Bourke

Return surface normal given a point on the surface. This function is normally called
after a displacement. For example:
P += displacement * N;
N = calculatenormal( P );
15.3 Color Functions
Several functions exist which operate on colors.
float comp ( color c; float index )
void setcomp ( output color c; float index, value )
These functions get and set individual color components. The index values are 0-
based (e.g., the green channel of an RGB triple is component 1).
color mix( color color0, color1; float value )
{
return (1-value)*color0 + value*color1;
}
Return an interpolated color value.
color ctransform ( string tospace; color C )
color ctransform ( string fromspace, tospace; color C )
Transform the color C from the color representation fromspace to the color representation
tospace. If fromspace is absent, it is assumed to be ”rgb”.
15.4 Matrix Functions
float comp ( matrix m; float row, column )
void setcomp ( output matrix m; float row, column, value )
These functions get and set individual components of a matrix. Strict runtime bounds
checking will be performed on row and column to ensure that they fall into the range
0...3.
float determinant ( matrix m )
Returns the determinant of matrix m.
matrix translate ( matrix m; vector t )
matrix rotate ( matrix m; float angle; vector axis )
matrix scale ( matrix m; point s )
Postconcatenates simple transformations onto the matrix m. These functions are similar
to the RI functions RiTranslate, RiRotate and RiScale, except that the rotation
angle in rotate() is in radians, not in degrees as with RiRotate.
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