How to calculate photometric angles in ISIS3 for ShadowCam images

[99YyLi]

I'm working with ShadowCam images and need to calculate photometric angles (ignoring secondary illumination effects) using ISIS3. However, I don't have access to the SPICE data or the camera model for ShadowCam.

Specifically, I need to calculate:

Incidence angle: the angle between the solar vector and the surface normal
Emission angle: the angle between the surface normal and the observation vector

I plan to use a specific DEM for this calculation. Could someone guide me on how to achieve this in ISIS3, given the lack of SPICE and camera data?