I've been playing with lighting up the large scale spacecraft of mine, and one thing I've noticed is the large number of lights I now have. For example, on the top and bottom sides of the main hull I have a series of ten navigation lights (point lights), so 20 total (top and bottom) for the port, and another 20 for the starboard sides. Another 6 spots on the top hull illuminating various bits, another 12 lights illuminating various internal docking bays (area lights). All told about 60 or more potential light sources.

This seems like a lot, but it does give the effect I'm looking for. My concern is that this is too much and is making the render slower than it needs to be. Currently all lights are set to have shadows ray traced. I tried using shadow maps but didn't like the results.

Are there any “tricks” to use when dealing with this many lights?

The scene itself is somewhat large in scale (the model is about 1.7km in length, with 1 houdini unit = 1 meter).

Current render times (for 1 frame) range from 4 minutes 50 sec to 7 minutes with the scene made of ~500K faces using the Micro Polygon renderer.

Have a tight falloff and use the Point Light Radius parameter to limit how far each light will affect things. That way outside the radius, the light will be ignored… obviously, you want the falloff to make it go to black before the radius cuts it off

Cheers,

Peter B

Peter,

Thanks for the tips. What is the “Point Light Radius” parameter? I can't find that in the Houdini docs for the Light object and I don't have Houdini in front of me, so maybe this is something that's not documented? Is this related to the Attenuation param?

Hi Jim,

Hmm. I don't have Houdini up either right now, sorry… it might be called something different, and I wouldn't be surprised if it was hidden in the Render Properties somewhere. Sorry I can't help further right now…

Cheers,

Peter B

jimc
Are there any “tricks” to use when dealing with this many lights?

Totally. PBR, because of the way it samples, isn't really set up to have loads of lights. A way I like to get around this is by doing all the main key lighting with actual lights, and baking all the secondary lighting (like the accent lights you're talking about) into a point cloud and passing that as emission to PBR. This lets you use lots and lots of lights Here's an example with 100 point lights with raytraced shadows. The bake pass takes a couple minutes, but the full on PBR render goes superfast. The nice thing is that in many cases you only need to run the bake pass once.

It requires a little bit of setup, but in some cases its totally worth it.

Good luck dude.

jimc
Peter,

Thanks for the tips. What is the “Point Light Radius” parameter? I can't find that in the Houdini docs for the Light object and I don't have Houdini in front of me, so maybe this is something that's not documented? Is this related to the Attenuation param?

It's called vm_activeradius. It specifies maximum distance any light is considered during evaluation of illuminance loops in shaders.

Thanks guys - I should note that I am NOT using the PBR renderer, that was a mistake on my part, I'm using the micropoly renderer, sorry for any confusion there.