Unreal Cascade: Spawn Location Falloff

jocose

I'm trying to create a particle effect using cascade that has particles that spawn over a volume. I was able to get this working by adding the "initial Location" module to the emitter and and defining the volume.

However the particles spawn uniformly with in my "cube".

Is there any way to make their alpha values, size or probability of spawning decrease at one end of the cube and increase at the other?

Oniram

trying to figure out what exactly you are trying to achieve here.. but it seems like you would just need to add a "size by life" function, and then just play with the curve editor to have it change size.

jocose

I have a volume of dust that is sitting in front of a light. The farther it gets from the light the less bright it will get because of the falloff of the light. I need some way to achive that.

Oniram

ah! had wondered if it might have been dust. you may be able to achieve that through the material editor.. frensel could do the trick for you.. this tut by Jeremy Baldwin goes over a really great way to get dust going.. and im pretty sure his vary by distance as well.

http://eat3d.com/free/dust_particles

jocose

I followed that to create the volume... I just need the effect to falloff in a particular axis...

ImSlightlyBored

spawn in spheres
do multiple components with spheres that get bigger, those that spawn within the larger spheres are less bright.

thats a simple way
if you wanted to get complex you can do this in the material editor
make a spheremask (Length between A, B / Scale) of ObjectWorldPos and WorldPosition (I think you might have to get OWP - WP instead of just OWP, not sure but its one of those two)
scale it to what you want, use that as a material fall off for your assets
Make sure your bounds are set correct in cascade and not automatic, else your mask will grow according to the center of the assets bounds (which seems to be how object world pos is fed in)

job done, falloff from the center of your particle system to the outside. Shouldnt be too bad as I guess your dust mites are real small. But I wouldn't do it like this (or do it at all) because it really shouldn't be too noticeable.

FURTHER EDIT
if you want it a specific axis or can mess around a little to get it just right on the cheap... just use particle macro UV and map in a falloff sphere/specific axis and scale accordingly.

There's alot of ways to do this, havent tried any. ill have a go later tonight but without a screenshot of your particle system its hard to tell how much shader bandwidth/specific fx you want.

last edit:
was this what you meant? (use constants, dont use divide use multiply by the equivalent, and dont use power etc etc)

fix particle bounds manually.

iono just an idea.

jocose

That would be cool if you could take a look at it, maybe post an example. I'm trying to learn all this but I have several other things going on the project right now and havn't had time to really dive into it yet.

Some examples would expedite that process greatly

EDIT: OH!, I didn't see your edit at first, the image link is broken! Can you fix it?

ImSlightlyBored

apologies
http://img121.imageshack.us/img121/2833/partyculls.jpg

since i posted last i found one thing out - fixed bounds on particles in the udk build i was using were really borked and flakey, don't work how im used to.
so instead of finding length between object world pos and world pos of the pixel, do a length of particle macro uv and 0.5,0.5, using particle macro uv in the particle system to scale it accordingly (make sure you divide by something small, as its not physical units now)

then go ahead and add the typical particle material stuff like vert color etc.