Noisy Refections in Glass

[pmaric]

I am using a mental ray dielectric shader for glass in maya. When I render the scene, there are areas where the reflections in the glass are noisy and I'm not sure how to get rid of the noise.

 

I've tried increasing the accuracy of global illumination. I've increased reflections, refractions, and max trace depth in both raytracing and final gathering options. None of the above helped, any suggestions?

 

[ATTACH]33995[/ATTACH]

[Companioncube]

i'm having the same problem but in Max, nothing seems to help

i’ve been trying to get back in mental ray after using vray for a while but already hit a problem. in the image you can see i’m getting some nasty speckle / noise / artifacting in the reflection of the glass. the scene is lit only by an object with an arch & design material with ‘self illumination (glow)’ turned on, a falloff map in the ‘filter’ color,with ‘Illuminates the Scene’ (when using FG) on. Final gather is only set to draft with 1 bounce, no GI or Caustics. the glass material is just an Arch & design preset of solid glass (no glossiness), but i tried the other 2 just to see if it was a bug but it appeared in all of them. i tried turing the FG up but that didn’t help, i tried turning up the Max trace depth in the glass, tried turning the BSP2 ......sorry i was just starting to try anything and everything.

the glow its self on other object/materials is fine, it only seems to be the reflection in the glass

only thing that seemed to help was turning up the sampling quality of the render, the top half of image is at 1/4 by 4, the lower half is i think 1 by 16. i also tried different filter types and cranked them up to blur it, but them the image blurs too much and the problem was still noticeable.

is there some way to fix this? has anyone come across this noisy (non glossy) reflections before, hoping the big dogs Mr.Zap and Mr Patton can help, thanks in advance.

(by the way using Max 2010 sp1 64bit)

 

(Part2)

given up, back to vray.

the problem seems to be with the refraction and reflection of the glass, but i’m suprised because neither are glossy which is what i would expect this kind of noise to be caused by.

i tried everything i could think of. was messing with the ‘advanced rendering options’ which dropping the refraction max trace depth down to 3 seemed to help the noise a bit. then i tried giving the glass a 0.99 glossiness value (in both the refraction and reflection) to see if i could get rid of it using the glossiness samples. tried cranking it up to 64 in both, then tried checking on Fast(interpolate) and messing with the Fast Glossy interpolation settings. all this just blurred everything way too much, which wasn’t the kind of glass i was going for, and still didn’t get rid of the problem. i tried brute force rendering but it didn’t help much either, with all these too the rendering time just up way too high.

anyone got any ideas? i’m going back to vray for now, but it would be nice if i could have a mental ray render too.

[pmaric]

thanks alex for your input!

 

your suggestion of turning up the sample quality of the render really helped.

 

here's what i did: in render globals, under anti-aliasing quality- raytrace/scanline quality, i increased the 'max sample level' from 2 to 7 and this completely got rid of the noise.

 

i'm using maya, i'm not sure how to do this with max.

[Companioncube]

glad you fixed it

 

so this morning i played more with the fast (interpolate) and Fast glossy Interpolation settings. I didn't want to play with these setting because it just blurs the reflection and refraction which wasn't the kind of glass i want but just wanted to see what would happen and if there was a way i could get back the sharpness once i tried to eliminate the noise. to make sure nothing else was interfering from the scene i applied a A&D material that is set to matte finish with a mid grey diffuse color.

 

image 1 + 2 have identical glass, the only difference is that image 1 is using the Max's Architectural Material with a luminance value of 100, but you can see Mental ray doesn't seem to like that material much. image 2 is using the A&D material with Self illumination on. just wanted to see if the architectural material made a difference after Samab suggested it.

 

so the glass settings in the renders below were the preset A&D solid glass but with these changes:

Reflection:

Glossiness=0.99

Glossy Samples=32

Fast(interpolate)=On

 

Refraction:

Glossiness=0.99

Glossy Samples=128

Fast(interpolate)=On

 

Fast Glossy Interpolation:

Interpolation grid density= 1(same as rendering)

Reflective interpolation:

Neighbouring points to look up = 5

High detail Distance = On and set to 10meters

Refractive interpolation:

Neighbouring points to look up = 1

 

Rendering Sampling Quality set to min 4 max 16.

 

So in image 2 you can see i almost got rid of the noise, but ended up with what looked like frosted/glossy glass which isn't what i was going for. i'm a sad panada

[pmaric]

hey alex,

 

i ran into a similar problem with a photon-casting area light that was creating unwanted hot spots into my renders. all i did was uncheck 'illuminates by default' in the area light attributes, and this helped to alleviate the problem.

 

i'm not sure if this would help you out at all, give it a shot....