[vtkusers] Doubts about ray casting class...

[Lisa Sobierajski Avila]

Hello Isabel,


>- Which the shading model that the method ShadeOn(), of the class 
>volumeProperty, does it use?

The shading model used for volume rendering matches (as closely as 
possible) the one used in OpenGL. It is a local illumination model that 
uses ambient, diffuse, specular, and specular power. Two-sided lighting 
also affects the volume rendered image.

>- In the same class volumeProperty (SetGradientOpacity), which is the 
>method used for the calculation of the gradient?

vtkFiniteDifferenceGradientEstimator is the class that performs the 
calculation - it is automatically created by the vtkVolumeRayCastMapper, or 
if you need to share one between mappers you can create it yourself. Beware 
that the gradient magnitude (used for the gradient opacity modulation) is 
transformed by a scale and bias prior to being stored in a 8 bit value. By 
default the scale is 1.0 and the bias is 0.0 but you can (and probably 
should) change these when working with unsigned short data.

Lisa