Pathlines: Show a glyph at the start point of advection

[sgpearse]

Pathines don't show anything at the first timestep of their advection, which can confuse users. Suggestion: show a glyph at the start point so that users know the renderer is functioning.

Question for @shaomeng: Would it be reasonable to set the default Pathline Length to 1?

[shaomeng]

Hi Scott, thanks for following up with that user. I kinda forgot to test the data he provided.

I agree that we want to reduce confusion to users, but for this particular confusion, I feel that the best approach is through user education like you just did, instead of changing the behavior of the software. I feel that a glyph itself is confusing: what does that mean in my data?

Also, I don't feel there's a big difference between default pathline length of 1 or the number of timesteps (current default value). The slider is front and center to be adjusted by a user. I think it should be a quite easy code change to make it 1, if you think that is a more reasonable default value.

[sgpearse]

Hi Scott, thanks for following up with that user. I kinda forgot to test the data he provided.

Hey, no problem. Hope your trip is going well.

I agree that we want to reduce confusion to users, but for this particular confusion, I feel that the best approach is through user education like you just did, instead of changing the behavior of the software.

The cost of this approach required 2 of our engineers to troubleshoot an issue over the course of 9 days. I'd say that's a high cost that could be zero if we did something intuitive.

I feel that a glyph itself is confusing: what does that mean in my data?

It would only indicate the starting locations of the pathlines at timestep 0. The user would at least see something when they turn the renderer on.

Also, I don't feel there's a big difference between default pathline length of 1 or the number of timesteps (current default value). The slider is front and center to be adjusted by a user. I think it should be a quite easy code change to make it 1, if you think that is a more reasonable default value.

Let's see what the team thinks. The pathline visualizations I've seen from Vapor and other software show parcels flowing in the wind (length=1) instead of a tube that grows along the path of the wind (length=numTS).

[shaomeng]

Ok Scott, I see benefits of either approach (w/ or w/o glyphs) and how they can both confuse a user. I'm fine with whatever the team decides collectively. Same with the default pathline length.