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Nangleator
07-17-2008, 07:54 AM
Cat: So, what is it?
Kryten: I've never seen one before, no-one has, but I'm guessing it's a white hole.
Rimmer: A white hole?
Kryten: A black hole sucks time and matter out of the universe, a white hole returns it.
Lister: (Puts hat on his head) So that thing's spewing time back into the universe.
Kryten: Precisely. That's why we've been having these curious time phenomena on board.
Cat: So, what is it?
So here's a sort of reverse tutorial. Follow this and you'll be stupider.

You want to create a stream of particles that are affected by a point source of gravity, like a planet or black hole. In a blank scene, create a particle emitter. Set the particles to live longer than 30 frames, but you can leave all the other settings at default.

Create a gravity object. Set the mode to Point. Set falloff to Inverse Distance. Play the animation. Hmmm. That doesn't seem right, does it? Particles are going outward, like the gravity is negative. Okay, change the -1 in the Y axis to 1. No difference. Okay, change the 100% power to -100%.

Now, we're almost getting somewhere. Particles fly in toward the center, then fly outward far faster. Not quite what we're looking for, but if we make a stream of particles fly past it, we might not notice the ones that hit the center and come flying out.

(We're trying to make an electromagnetic lens effect with particles. We want a dispersing stream of particles to be bent towards a centerline as they travel forward.)

Okay, so we'll resize the gravity object downward so the effect is over a smaller area. What the... As we resize downward, half those yellow lines grow back outward. We actually can't shrink the gravity!

What do we do next? Create a collision object near the center to kill off any particles that come too close to the center? So we don't get those embarrassing particles exploding outwards?

Nangleator
07-17-2008, 08:22 AM
Okay, I've calmed down now, and learned a bit about Point mode gravity sources. 100% power way too extreme, unlike 100% power in a wind emitter, which might as well not exist, for cloth simulations, anyway.

It's pretty important to keep particles flowing past the gravity source in order to keep them flinging through the center, which looks pretty ugly.