Light-Camera-Glitter Simulation

In one of my last blog posts, I discussed the preliminary results of trying to optimize for both the camera & light locations simultaneously. I have been working on a simulation of our geometry to try and understand this better. To recap, it seems that there is a slight ambiguity in the position of the light and camera, in that they can move slightly along two rays and still give a lower error. One thought is that it is an error in how we are modeling the light and the gaussian receptive field of the glitter. Another thought is that it may have to do with the fact that our light is not a point light source, but rather a small square; so we don’t quite know what part of the light a glitter piece sees. More likely is that it some combination of these two issues.

In this blog post I want to highlight where I am in the simulation, and what it shows so far. I simulate 10,000 pieces of glitter that lay on a place, each with a surface normal corresponding to some random screen location. 500 of them (chosen at random), however, have surface normals that allow the glitter to see the simulated point light and the simulated camera. For those that ‘see’ the light, I give them intensity values of 1, and give intensity values of 0 for all of the rest.

I then compute the predicted intensities for each glitter pieces using a few different gaussian values for the light and the glitter receptive field. Below, the non-yellow rays are the pieces of glitter that have actual intensity values of 0, but predicted intensity values between 0.1 and 1.

The above images are made using a light gaussian size of 5 and a glitter receptive field of 40. As the predicted intensity gets higher, the rays getting lighter (and farther away from the camera), which is exactly what we would expect to happen in this system.

Next, I am adding in the actual ‘optimization’ part of the simulation. As a first pass, I will just optimize for everything (including light and camera) and see what happens. In doing that, I hope to understand what parameters to tune, and I can start fiddling with the way in which I am predicting intensities and how I am modeling receptive fields.


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