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Is there a way to have particles spawn and die only within the confines of a mesh?

Like If I wanted to simulate dust motes illuminated by a lamp using a spotlight component, I'd want to make a cone shape in which the particles spawn, and die within the time limit or when colliding with the wall of the cone. Thanks.

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asked Jul 30 '14 at 02:29 AM in Using UE4

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Hey swiss_cheese9797 -

The most efficient way to achieve this effect would be a singular cone or billboarded plane with a material like the one below assigned to it would generate a good limited dust effect. You could always use the timing of your particle system to try to get something like a cone in Cascade, but you will loose a lot of the random motion which sells the dust effect itself.

For something with a large scope so like a factory industrial light where the cone is really large you could do a triggered effect tied to your character's movement so you span the dust motes when in the cone and have them fade out when you are out of the cone.

For a smaller scale like a table light or a spotlight in a limited size (like in an office) modeling a small cone with no top or bottom and applying the material below to it would give you a much better effect. You will have to spend some time working on your texture to make sure that your dust particles look the way you want them to and that your fading mask fades as you need it but it will be processor friendly and give you the desired effect.

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Thank You -

Eric Ketchum

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answered Jul 31 '14 at 03:48 PM

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Lovecraft_K ♦♦ STAFF
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avatar image swiss_cheese9797 Aug 03 '14 at 01:07 AM

Hey thanks man. I'll try this out, but I'm anticipating it won't have the nice look of random floating particles that an actual particle effect would have. Know where I can find that texture file? I really wish the cascade "kill box" worked like they say it's supposed to. That would solve all my issues but for some reason they didn't make sure it worked right. Didn't work right in UDK either.

avatar image Lovecraft_K ♦♦ STAFF Aug 04 '14 at 01:58 PM

Hey -

If you spend time on developing your own texture it look pretty nice. I am attaching to my very quick texture I used to test the effect, but to upload it I had to reduce its size by 50% (from 1024 to a 512 texture size) and I changed from a TGA to a PNG (both should work fine, but I tend to like to work with TGAs). Of course the other aspect of this working is the cone mesh itself and laying out your UVs in a way to work with the panners. You could also add teh cone into a Mesh Particle System and have the whole Mesh fade in and out over time as well as rotate it about Z for even more motion.

Regarding the kill box, if you want feel free to state you issues with how you think it should work as a new question in Rendering of the AnswerHub and I will look into it for you.

Good Luck -

Eric Ketchum

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