View Full Version : Particle birth rate texture bug?

12-31-2007, 05:19 AM
Hi, just wanted to see if anyone else has this problem, or if anyone has a work around. This has completely stopped the work I'm doing and I can't think of how to get around it...

I have an actor being shot with a laser gun and I want them to dissolve away with particles, like embers or ash blowing away in the wind, something like that. Anyway, I've managed to extract a matte from the footage of the actor doing his death throws so I just thought that I'd use that as a texture for the particle birth rate.
But there seems to be one small problem; it just doesn't work. 'it' being any image texture on the birth rate. And when I say 'work' I mean that the particles birth locations are not confined to the desired location, if any are born at all. The birth rate seems to be massively reduced when using image maps.
I'm using 9.3.1 and I'm currently downloading 9.3.0 to see if it has the same problem.
Procedural textures seem to work just fine, it's just image maps (I've tried png and jpg formats so far).

Anyone else?

12-31-2007, 05:27 AM
Well uvs dont work right... the rest of the projections work good, but you have to set the birth rate to per frame and crank the particles up to high numbers. You also might want to put a previous layer gradient over your texture and crank the amount up that way. good luck...

12-31-2007, 05:43 AM
It's the same in 9.3.0.
Thanks for the reply oldtekerr. I'm not using UV projection, birth rate is already set to per frame and if I put the birth rate up to high numbers, I just get particles appearing all over the place and LW grinds to a halt because (I guess) it's calculting things for tens of thousands of particles behind the scenes.
Furthermore, if I hit the calculate button, it completely ignores the texture altogether.
I'll try the gradient thing...

12-31-2007, 06:02 AM
here is a test that worked for me... just calculate...

12-31-2007, 06:20 AM
That one works fine on my system too. Just seems to be the animated texture that doesn't work...any chance you could use this image sequence and test...

Note: Its actually a 7-zip file, but NT wont allow those to be uploaded so I renamed it to a zip file. Try to use 7-zip to unpack it if you can.

12-31-2007, 06:37 AM
you should be good...

12-31-2007, 07:22 AM
OK, this system is totally weird. I'm using a 16:9 plane to map these particles onto and the plane is attached to the camera so that it fills the view, just so it matches up with my 16:9 footage.
When I try to map the image sequence onto the plane (on the z axis) and hit automatic sizing, nothing happens. It stays at 1m x 1m x 1m, so I have to change it to 1.7778 m x 1m x 1m manually, otherwise the emission doesn't line up. Hit calculate...I've only got 3 particles now. Right. Open the texture editor for the birth rate and click on a layer...now I've got 2757 particles. Scrub through and one point particles stop being emitted, probably something to do with the 1000000 upper limit there seems to be, not that I've actually got that many particles.
Oh, and also, when I scrub through, particles are emitted in the wrong place unless I've got one of the layers in the texture editor selected.
This is totally rubbish.
oldtekker, if you have time, do you want to try it on a 16:9 plane (1.777m x 1m x1m) and see how yours behaves? I'm going mad...

12-31-2007, 07:48 AM
ok...Look at the gradient. The negative numbers is what is keeping the particles from emitting where you don't want them... and the automatic size isn't working because its sizing it to the emitter, 1x1x1.

12-31-2007, 08:42 AM
Ah ok. Thanks oldtekerr, I'll run with this and see if I can get it doing what I require. Thanks for all your help - but I may well be back later pulling my hair out :)

12-31-2007, 08:52 AM
I will agree that... THIS SHOULD ALL BE MORE INTUITIVE (NT if your listening). The only reason I knew all that was because I just was trying to do something very similar... and it took me a day just to realize that UVs were broke and to stop wasting my time! Hope it works out for you...

10-05-2011, 05:26 AM
Sadly, 3 years later, we're at version 10.1 and its still exactly the same. Not even a hint or tip in the manual.

10-05-2011, 06:20 AM
If it hasn't been logged as a bug, then they may not know about it! Please can you log this as a bug on Fogbugz! :)