Light inside Glass PBR noise

[blackchicken]

Hello guys

I starting to prepare upgrade my reef system and do some previz in Houdini ofcourse . I found little problem here, If I add 3 arealights (blue, warm white, blue) into the aquarium cover, bouncing light on glass create a lot of noise. I try to add samples but not big change.

Settigs

Houdini 11 Manra PBR:

Samples 6x6

Ray 1.9

Noise level 0.01

Diff limit 1

Color Limit 4

I use default glass shader.

Which parameter is connected with this noise? I could render with samples 4x4 5x5, noise on white areas is ok. But this glass noise cant smooth. Thanks a lot. B.C.

[Erik_JE]

Glass is a pain with PBR.

Try even lower Noise level and higher Samples.

[blackchicken]

Ouch, that will be painful. No other solution? Thanks a lot Erik.

[Erik_JE]

Only other thing I can think of is reducing reflect and refract limit as much as possible without the render starting to look wrong. 5-6 should probably be enough for both. But that will probably just help with render speed more than the noise.

[lukeiamyourfather]

I would guess the noise is from either the area light samples or the Fresnel blending on the glass (or both). Try increasing the area light samples on the light itself. If that has no affect then set the samples lower on the light and increase them on the Mantra driver.

[Erik_JE]

Increasing area light samples greatly increases render time tho. With PBR you are usually better of increasing the actual pixel samples.

[dennis.albus]

What I usually try to do is exclude the glass from the light and create geometry with a constant shader just for reflections/refractions. Most of the time this helps. Also try to carefully include only the objects you absolutely need into your refl/refr.

Sometimes it also helped to increase the specular angle on the glass material just slightly. Of course it's not correct, but if you don't need crystal clear reflections you could get away with it.

Limiting the refl/refr limit as low as possible is also a good tip (as suggested by Erik_JE).

Other than that I just finished a project for a light manufacturer who also had special lights that illuminated glass sheets from the inside and made them glow. In that case the easiest way was to just fake the effect with some carefully placed gradients.

-dennis

Edited April 10, 2012 by dennis.weil

[blackchicken]

What I usually try to do is exclude the glass from the light and create geometry with a constant shader just for reflections/refractions. Most of the time this helps. Also try to carefully include only the objects you absolutely need into your refl/refr.

Sometimes it also helped to increase the specular angle on the glass material just slightly. Of course it's not correct, but if you don't need crystal clear reflections you could get away with it.

Limiting the refl/refr limit as low as possible is also a good tip (as suggested by Erik_JE).

Other than that I just finished a project for a light manufacturer who also had special lights that illuminated glass sheets from the inside and made them glow. In that case the easiest way was to just fake the effect with some carefully placed gradients.

-dennis

Thanks a lot Dennis, good tips Ill definitely try this.