Particle sizes change depending on the data

[zhafen]

This is demonstrated in the screenshot below, which shows a 100x100x100 ruler shown for two different data sets. Note how the ruler is much thicker in one data set than the other, despite the ruler point size being set to 4 in both data sets. This can be pretty extreme, and makes it hard to look at detailed behavior in some cases.

As far as differences in the data that could produce this, I think it might have to do with the scale of the data not currently displayed. For the first data set the data goes out to a much larger distance than the second data set.

[zhafen]

This can also be seen by comparing the rulers in time-fly and Latte-CGM. Both are 100x100x100 and have a pointsize of 4, but look different.

[agurvich]

Might have to do with the definition of particle "size" as the number displayed in the app is sizeMult, a multiplicative factor applied to the "true" particle "size."

[ageller]

I may have fixed this in the flaskGUI branch. I created a notebook in there as well called testParticleSizes.ipynb to play with this.

Some explanation: The particle sizes are a bit complicated because they depend on the camera location. Previously we normalized the size by the total extent of the data so that a point size of 1 (for example) is the same relative size no matter what the extent of the data is (e.g., 1 would be very big physically for a physically big system). I removed that normalization. But then there appears to be some magic number of about 70 that I need to multiply the sizes by in order for them to represent the physical size of the point. I don't know where this comes from, but it seems to work in the limited examples I've tested.

For the isolated galaxy example, a point size of 1 looks pretty good. I don't know if that makes sense (e.g., are the units in parsecs?). Thoughts?

Please test this on your end!

[agurvich]

It may be impossible to do this on all systems because different drivers have different ALIASED_POINTSIZE_RANGE variables (and even my computer went from [1,64] to [1,511] since the last time i checked so apparently it can change???)

webgl settings can be viewed at: https://webglreport.com/ which reads your machine's driver info and formats it nicely in the browser