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View Full Version : Things that Go Bump with the Light...



Richard Hebert
04-30-2019, 07:54 PM
Hi Everyone, I'm seeing an issue that I can't resolve. I'm very new to Lightwave 2019. Lots of changes and upgrades. I've got a double sided cylinder with a texture and bump applied to it. The cylinder has two spherical light sources inside mimicking light bulbs. When the lights are on I'm getting specular hits on the outside of the cylinder where no light can reach. I thought the spec hits were from the environment at first but disappear when the lights are deactivated and the scene renders out as expected. Has this been noticed by anyone before?

lardbros
05-01-2019, 12:47 AM
Hmmm, that seems very odd indeed.
Can you post the scene? Might be easier to determine what's wrong by looking at the scene files.

Tobian
05-01-2019, 03:41 AM
It's almost certainly from triangulation errors.

Try running this https://www.lightwave3d.com/assets/plugins/entry/normal-corrector/ and then unify polygons (and flip if anything got inverted).

I'd also look in the two sphere lights, and check if they have a falloff node in there, if so, take it out, and set their falloff to Inv Sq as standard. Having falloff off, or the use of the faloff node can cause noise/blowout/render slowness issues.

Richard Hebert
05-01-2019, 04:19 PM
The cylinder is made of quads with polys facing inward and surface double sided. Lights are spherical with inverse square.

Dan Ritchie
05-02-2019, 10:37 AM
It looks like the spec is coming entirely from the environment light, and on the backplate of the tube, I see a reflection from the image world.

RebelHill
05-02-2019, 10:54 AM
Yep... its the enviro, turn that off, those external specs go away even with the interior lights on.

Richard Hebert
05-02-2019, 11:39 AM
Why do they vanish when I turn off the interior lights?

RebelHill
05-02-2019, 12:20 PM
Ok... so I dont get the same problems with the render you're seeing, but I do get something weird, that's similar though less severe.

However, after a deeper look and similar to what Tobian initially suggested, the problem is your model. You have single poly thickness to the "hull" (essentially infinitely thin), and the light/lamp glass mesh up against it. Thats a recipe for fractional poly intersections leading to light leaks right there.

Dan Ritchie
05-02-2019, 12:33 PM
Because Specular in 2018 onward means reflection of any light, and not just a sun/lightbulb type reflection.

Richard Hebert
05-02-2019, 04:25 PM
The lamp modeling was thrown in because I thought the bare spherical lights were contributing to the render problem. The problem existed before the "lamps" were made. I don't mind thickening the geometry if it helps with these kinds of issues, just never experienced this in previous versions (11.5 and previous). Thanks for all the input, it's helping me to understand the new version a little better.

Richard Hebert
05-02-2019, 06:29 PM
Thickening the geometry eliminated the artifacts. Wow, that's going to be a lot of geometry to modify to make all of these lights work. What exactly does the environment light do if it's not needed to use HDRIs?

RebelHill
05-03-2019, 03:21 AM
Its not needed for HDRI, but it's useful for them, better than using the image as BG GI. As for the mesh, in much the same way as the new renderer in all "physical" and such, you really need to make your geo "physical" for best results now. Some of the ugly lil things you could get away with in the past dont always work out so well... see here...


https://www.youtube.com/watch?v=saRXQ9VYWsw