ISIS Photometric Angle Calculation #5275
acpaquette
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From some discussion on issue #5197 there was an inconsistency introduced in ISIS 7.1.0, where the internal state of the
DemShape
class was introducing new behavior to the parent classShapeModel
.As of 7.1.0 and up when the
Camera
computes the "local" angles (emission, incidence, etc.), those angles are based off some local normal calculated by the underlying shape model (DEM, embree, bullet, etc). This had the unintended side effect of computing a local normal based on the shape model, that would then be used in the regular emission, incidence, etc. Prior to 7.1.0 these angles would use the ellipsoid normal vector rather than a higher resolution shape model normal vector or "local" normal.What is the intended behavior here and what should be the resolution? It seems like this was handled in other models, see the EmbreeShapeModel and how that class handles it's state. Saving the current normal, computing a new normal from a more detailed shape model, getting the requested angle, then resetting the normal.
Ideally, I would like to come to some consensus on what normals should be used. Right now we have something like
phocube
that gets the ellipsoid emission, incidence, etc but can also compute the "local" emission, incidence, etc. Alternatively, the current camstats app uses the more detailed shape model to compute the emission, incidence, etc. with no knowledge of a "local" normal or local angles.Is there need to see multiple photometric angles at any given point, would it better to provide an option for users who are using higher resolution shape models to compute those angles with a lower resolution model? Given the changes we have seen in the past decade with more detailed models becoming available it may be worth accessing this.
Another option provided by Jesse in #4611 would potentially have some implications for use in various apps like camstats and phocube where you could ask for those photometric angles to be computed with a lower res shape model. It would also make it more obvious to users that those models are still available even if they used a higher resolution model from spiceinit.
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