Hidden from camera option still renders heavy geo (but like a holdout)

[Gunnah]

I'm using Next for this (haven't checked 5 yet but our show is locked for Next) but basically I've been noticing for a while if I have say 20 trees overlapping and a ground plane, if I make the trees not visible to camera, I still get what looks like matted out tree parts over the ground plane (this is in beauty and alpha has holes) I'm thinking that it's the ray depth, and vray saying pretty much "you'd never in a million years see that anyways", so just disregards the remaining things anyways, but it does pose problems occasionally. I was wondering if this is non issue in 5, or if its something that can't be worked around? Just note this happens with vray proxy/hair/heavy geo/trees etc. Anything with a lot of semi transparent or transparently mapped objects.

cheers in advance

cp

PS: I did attempt a search for a topic on this but too many variables

[hermit.crab]

Could you share a screencap/simple scene? Not sure I understand what you mean. Maybe you're seeing the object's shadow (try disabling "Cast shadows" as well)?

[Gunnah]

yeah I'll have to get one of the devs here to send to you (image) I'll try and make a simple repro as well. Basically, to repro you make say a character with hair, then make the hair non visible to camera but cast shadows on things around it (like skull whatever) if the hair is dense, you will get black holes like the hair is a matte object, but alpha is also black where hair is, so you cant get a clean shadow only pass. Same for trees, make a pile of trees with some opacity mapped leaves and put it on ground plane. Render with not visible to camera enabled on the trees and it should give same result, black holes everywhere the leaves are overlapping too much. (raydepth) and no matter what you set raydepth at, you'll never get rid of it. It affects all AOV's as well. I'll try and get a repro for you and images tho.

ps: ill try with shadows disabled, but the point is we want the shadows from the things onto they other things, and not render the things casting shadows

[Gunnah]

ok have a repro for you, super simple:
1. make a teapot and a plane under it (teapot 10 units, plane 140x140 w/l)
2. make a vrayLight and point it at the teapot to light
3. put vrayfur on teapot, set to per face with value of 84 (should be REALLY thick) assign vray fur shader doesnt matter the settings
4. render. Result should be a big pile of fur on teapot.
5. make the fur not visible to camera in object properties
6. render again. Result should be a black hole where the fur is overlapping a lot, on screen and in alpha. (just tried no shadows and it still makes holes)

this is max 2020 and vray next update 3.3 build 30575 (will try in 5 as well)

[Gunnah]

oh I should mention embree doesn't make a difference either

[Gunnah]

(you should have a repro scene now) it didn't work in 5 as well :/

[Morbid Angel]

I'm using Next for this (haven't checked 5 yet but our show is locked for Next) but basically I've been noticing for a while if I have say 20 trees overlapping and a ground plane, if I make the trees not visible to camera, I still get what looks like matted out tree parts over the ground plane (this is in beauty and alpha has holes) I'm thinking that it's the ray depth, and vray saying pretty much "you'd never in a million years see that anyways", so just disregards the remaining things anyways, but it does pose problems occasionally. I was wondering if this is non issue in 5, or if its something that can't be worked around? Just note this happens with vray proxy/hair/heavy geo/trees etc. Anything with a lot of semi transparent or transparently mapped objects.

cheers in advance

cp

PS: I did attempt a search for a topic on this but too many variables

I suppose its normal, when you deal with raytracing and ray depths. Since if you have an object invisible to camera it still has to cast shadow and therefore trace rays through it the material is optimized not to do too many raytraces, but it may not be desired effect for layering objects. In any case, its max transparency levels in material option under global settings. I don't have max installed anymore (moved from it long ago) but in maya its here (screenshot attached) Once you find that value set it to like 250 or 500.

[hermit.crab]

Morbid Angel is right (in 3ds Max the setting is located in: Render Setup>V-Ray>Global Switches), though for very thick hair, the option should be pumped up, which slows rendering quite a lot. Also, note that with a hair as thick as in that, the object will be in full shadow.

[Gunnah]

yes, thats why I made the hair that thick, so its in full shadow. The point is, the hair is *not* vis to camera, and unless (in this particular scene I sent you) you turn the raydepth to 1250 minimum, it leaves black holes everywhere. So what you're saying is there's no other alternative to fix this correct? The worst part of this is you cant even do a matte shadow pass properly. In any case, we sent you guys a repro scene, if this is the only way then I guess we'll have to find another way to do it.

thanks

cp

[hermit.crab]

Yes, I already looked at the scene you sent and the solution is the one already mentioned. Otherwise, what exactly are you trying to achieve? Wouldn't rendering the hair separately (and probably its shadow) separately to be later comped in post suffice?

[Morbid Angel]

I ran into this issue a lot, since you comp your object over top of the bg anyway its almost never an issue. What is the problem you are having with it? I suppose you split them out for comp purposes.

[Gunnah]

Hey Dmitry
Yeah most times its never an issue but we had a show where we were doing. some crazy huge terrain and trying to get a clean (for example) atmos pass and terrain pass with no trees was a huge pita. In this case when the trees were hidden from camera, the aerial persp was fullbright wherever there was a hole, for example so you couldn't screen over anything without some weird issues, that kinda thing. Yes we split everything here (@Scanline)

Yes, I already looked at the scene you sent and the solution is the one already mentioned. Otherwise, what exactly are you trying to achieve? Wouldn't rendering the hair separately (and probably its shadow) separately to be later comped in post suffice?

Yes, thats exactly what we're trying to do here (render hair separately along with separate shadow pass..) with no holes in alpha.