Attached Link: http://www.cornucopia3d.com/forum/viewtopic.php?p=10934#10934

and a belated Happy Christmas to you.

The holiday season having given me a bit of time to get on with some Python coding, and I've started with rain. The cube in the attached image is just there to check that collision detection was working; i.e. it doesn't rain under the cube. The script, and link to a test animation are avilable on C3D forum at the attached link.

Cheers,

John Edited coz my "a" key keeps sticking

Message edited on: 12/26/2005 14:31

Code resources at long last! Thanks much John! "Keep 'em flying!"

Congratulations, John! Very nice job. I hope you are so successful that you put me out of business! Pam

Pam, far from putting you out of business, I was just about to purchase your Stormy Rain Package with a view to writing some scripts for those specific models. There is a great rain splashing into water script that ships with V5i, but for drops hitting roofs and windows I think geometry such as yours becomes neccessary. John

Hi John. I see that you purchased it and are going to try it out. Please let me know if you need anything changed. Next week (late in the week), I can go to work on trying to make a series of meshes for splashing rain, if that is useful. I've programmed in the past, so I'll also try to take a look at your Python scripts for this, next week. This should be very cooooool!!!!!

This should be very cooooool!!!!!

I hope so! There's a number of improvements I can see the script needs, relating motion to time rather than number of frames being the most important. I know tht average rain drop reaches the ground at an velocity of around 1 metre per second, but what about a drip from a tree branch or roof edge? How quickly do they accelerate, and how can real world distances be related to Vue units? Lots to think about here. :)

Well, John... After looking into a lot of these physics, it appears that pure transit velocities tend to be VERY gross averages. Most rain is accompanied by wind, of course, and therefore massively variable. So, the purely atmospheric these transit rates could be almost anything that looks reasonable. There is some data on how long it takes for drips to form, given various surface roughnesses, shapes and cohesion, however. I'll go dig that stuff up.

"these transit rates could be almost anything that looks reasonable."

Point taken, but one has to start somewhere and there's a lot of empirical data out there says 1 metre per second. I read an interesting paper, that I can't find now (typical for internet research), by the guy who did the particle systems on the early Star Trek movies. He defined the effects of wind on rain, and fire hotspots on smoke, as rotating spheres of turbulence that add, or remove, gravitational pull to paticles. Does that fit with your photographic observations? Message edited on: 12/27/2005 13:46

For the "hotspots on smoke", yes, that makes sense. I don't thinks so, for the rain. By "gravitational pull," I assume you mean "attracting other particles." Nothin like that is noticable in the rain imagery. There are turbulence patterns in rain - but still separation between the particles is very noticable.

Sorry no, I meant gravity in the sense of a down force in a particle system. Typically particles also have an energy attribute which is like an ant-gravity force. So I also wrongly explained the rotating spheres, they add energy to particles entering their leading edges, and remove it from those at the trailing edges. I hope that makes some sort of sense, I'm still looking for the original article, the author knew how to explain stuff!