Max depth calculations

[tricky]

I'm wondering if anyone has any tips for working out the max depth of reflections (or refractions for that matter) on vray materials? I assume that we should try to keep this figure as low as possible to increase render speed, but when we have panes of glass, through which we see other reflective surfaces (chrome taps, marble floors, shiny surfaces etc), I start to get confused with which materials the max depth figures need to be increased.

In my current scene, I am looking from outside a window, through to a 'posh' bathroom. The bathroom has polished marble walls, and on the wall is a chrome towel rail. Without the glass in the scene, everything looks OK with my max depth values of the marble and chrome set to around 3. When I put the glass in, the chrome towel rail goes black, and the reflections seem to disappear from the marble. Is it the max depth figures on the chrome and marble that need to be increased?

Is there any sort of utility that might help me out?

What workflow do you follow on these occasions? Do you just up all bounces to 20 in the global switches rollout (for example) and not worry too much about increased render time?

[Macker]

I rarely have to set the max values at anything other than the default settings, and usually only go up from there not down. They generally don't seem to affect speed that much, certainly not enough to worry about on a still render. If I were doing animations all the time it might be worth considering.

[tricky]

I rarely have to set the max values at anything other than the default settings, and usually only go up from there not down. They generally don't seem to affect speed that much, certainly not enough to worry about on a still render. If I were doing animations all the time it might be worth considering.

In this case I am talking about animations. Having said that, I don't really have a render speed comparison between 'optimizing' the max depth and sticking with default values. It would be great if Vray could have an option to calculate max depth 'on-the-fly' to a certain threshold.

[Pixelcon]

I've only tried it once, but you can use VMC to turn the reflection exit colour to a really offensive and easy-to-notice colour. turn the depth down to something low and start to adjust until the exit colour disappears. Give it a shot.

[tricky]

I've only tried it once, but you can use VMC to turn the reflection exit colour to a really offensive and easy-to-notice colour. turn the depth down to something low and start to adjust until the exit colour disappears. Give it a shot.

Thanks James - useful suggestion! (I still want vray to automate this!! lol)

[vlado]

It would be great if Vray could have an option to calculate max depth 'on-the-fly' to a certain threshold.

V-Ray already contains a lot of logic on that topic; the cut-off threshold being one; in V-Ray 3.0 there is some additional code concerning this as well.

Best regards,
Vlado

[joconnell]

Only rule I have is that the glossier the reflections, the lower the number of bounces I give it. The very first bounce you'll get some sharp detail for objects that are close to or are touching off your reflective surface, things that are further away or on the second bounce are pretty blurry so only add in some ambient brightness change. If you've got sharp reflections then that's a different story.

[3DMK]

You could also Turn OFF the glass & render your scene normally...then render just the glass & comp it together. That way you don't have to worry about your reflection depth!.
Hope this helps

[Vizioen]

You could also Turn OFF the glass & render your scene normally...then render just the glass & comp it together. That way you don't have to worry about your reflection depth!.
Hope this helps

Doesn't this affect your glass having no reflections of its surroundings?

[Neilg]

he doesn't mean in it's own scene. as a pass.

save a copy of your scene, select the glass, invert selection, go to vray properties and check on matte object, alpha contribution -1, change reflection & refraction gi's to 0 and check on no GI on other mattes. make sure the environment color is black.

because you're comping it you dont need refraction either - render it fully reflective and grab a fresnel falloff from the extra tex element to use as a mask when comping.

Changing the max depth makes a massive difference to render times, i've taken scenes down from 6 hours to under one by going through all the materials to optimize depths. 5 is obscenely high and is even higher than you need for glass if you do it in post. set everything to one, materials with glossiness around .8 change to 2, any higher and change to 3.
It's that high by default because otherwise vlado would have a thread every week here asking why materials look different when they're seen through 2 layers of glass. if you stop rendering glass (or mirrors, anything with a glossiness of 1) in your base you can cut render times down so much.

[AlexP]

How do you deal with refraction effects, distortion/fog etc with this approach? (rendering glass as a separate pass)

[tricky]

You could also Turn OFF the glass & render your scene normally...then render just the glass & comp it together. That way you don't have to worry about your reflection depth!.
Hope this helps

We sometimes use this approach.

[tricky]

Changing the max depth makes a massive difference to render times,

This is what I figured, but wasn't absolutely sure. I do know that having large panes of glass close to the camera (even with glossiness set to 1) and rendering the glass in with the rest of the scene can be VERY slow indeed. Vray does seem very good for optimising scenes with lots of blurry reflections and soft shadows - we can actually get pretty good render times. But as soon as there are large panels of 'simple' glass that take up a reasonable size of the frame, the render times can go through the roof.

By 'simple' I mean black diffuse, white reflection (fresnel ticked on) and white in refraction.

[mcnamex]

sorry to bump this thread. Any solution to this yet?

[vlado]

sorry to bump this thread. Any solution to this yet?

Can you be a bit more specific? There were a number of things discussed in the thread.

Best regards,
Vlado