Points generate light

[Adam Ferestad]

Hello all again, new day, new project. This time I am trying to do something that I had assumed would be a simple task, but is turning out to be quite to the contrary. I am trying to get scattered points to emit light. Initially, I thought I would be able to use a copy node with lights and have them still emit light, but that was a no-go. Then now I thought maybe I could apply a glow material to the points with the glow color overridden, but again, that seems to not work. So my question is, how do I make points emit light? I want just the points to emit light, not the entire surface. I know in 3ds, I can use scatter on a light and still maintain the properties, though they are a little bit harder to deal with than in Houdini, which is why I was hoping that this project could gel faster.

christmas_tree.hipnc

[tony]

Hi,

Have you seen this post:

I think it may be what you're after.

Cheers

Tony

[Erik_JE]

Creating a geometry light from the points might work as well.

EDIT: Just want to add that this is sh*tloads faster than instancing if there are A LOT of lights.

Edited June 6, 2011 by Erik_JE

[hopbin9]

Create a point light, then an instance node. Have the instance node reference the point light. Turn on point instancing, and inside the node object merge your points.

You can then override properties to control the color and intensity of each point light.

[Erik_JE]

Small simple example.

particlegeolight.hip

[Adam Ferestad]

Thanks Erik, that did the trick, mostly. For some reason my lights are shifting each frame, which they shouldn't be. I have them set to a steady color like you did with the rand($ID+n) where n is 0, 1 or 2. I was trying to get them to fade in and out using a sin function, but then I got the points looking like they were jumping around on my tree, and that just didn't work for me. So I took out the dimming/brightening part and rendered it again and it was still doing it. No clue why, since there should be nothing to move the points/particles around.

The other thing I am trying to figure out how to do is get the geolight to render a smooth lighting without cranking my samples through the roof and killing my render speed. That is a problem I am having on all of my scenes though. I can't figure out how to get smooth lighting without setting my light's sample rate to something ungodly like 150. How do I get Mantra to play nice with me?

christmas_tree.hipnc

[Macha]

I only had a very brief peek at it. Does this help?

christmas_tree.hipnc

[Erik_JE]

Thanks Erik, that did the trick, mostly. For some reason my lights are shifting each frame, which they shouldn't be. I have them set to a steady color like you did with the rand($ID+n) where n is 0, 1 or 2. I was trying to get them to fade in and out using a sin function, but then I got the points looking like they were jumping around on my tree, and that just didn't work for me. So I took out the dimming/brightening part and rendered it again and it was still doing it. No clue why, since there should be nothing to move the points/particles around.

The other thing I am trying to figure out how to do is get the geolight to render a smooth lighting without cranking my samples through the roof and killing my render speed. That is a problem I am having on all of my scenes though. I can't figure out how to get smooth lighting without setting my light's sample rate to something ungodly like 150. How do I get Mantra to play nice with me?

You do not wanna crank up your samples on the light. It is better to decrease your noise ratio and increase your pixel samples in your mantra node.

[Adam Ferestad]

Well, that got the rendering issues solved. Now if only I could figure out how to make the color of each particle not be reassigned each frame. I took out all but the rand($ID) values for the color node in my popnet and I set a non-preserved birth group and have it apply only to that group. In my mind, that should make it apply the color to them only on the first frame and then the attribute is locked for the remainder of the scene. Unfortunately it doesn't seem to be working quite like that.

I checked out the particle light file that Erik posted and it's not having this issue, but the settings are the same. My network has fewer nodes because I am not having mine move at all, but the color nodes are identical. Also, the colors in the Details view and the the curves when I scope the color from the node are all saying that it's not changing, but each frame, all of the particles have a new color on them. I rendered out two concurrent frames and in the first, a particle was green, the next it was red.

@Marc: That helped me out a ton on the rendering stuff, thank you so much. Also, the dimming is nice, and I like how you did it, but I was more aiming for having each particle dim and brighten individually, as opposed to the whole tree. I know it's not quite realistic, but I am trying to figure it out so I can know.