Implementation of Raytrace Support

The Lens class provides three functions to represent the lens potential \psi^.

• psiValue( double, double ) evaluates $\psi^R(\theta_1,\theta_2)$

• psiXvalue( double, double ) evaluates $\frac{\partial\psi^R}{\partial \theta_1}(\theta_1,\theta_2)$

• psiYvalue( double, double ) $\frac{\partial\psi^R}{\partial \theta_2}(\theta_1,\theta_2)$

For subclasses of PsiFunctionLens each of these are hard-coded for the specific lens model. For SampledPsiFunctionLens each function looks up the value in a sampling matrix which is computed when the lens is instantiated. The lens object is intantiated with an instance of PsiFunctionLens which is used for the sampling. The derivates are computed with a Sobel filter.

The Raytrace Model depends on the last two to compute the distortion.