Streamline backplate integration workflow

[^Lele^]

[...] but I recall in several threads here that matte object having issues with GI rays. In some discussions Vlado would simply mention that in order to get perfect shadow pass and perfect integration in post, you need to render the scene twice, no other workaround. [...]
The darker edge is an example where a trick (or in better way "some setup") needs to be done to ease out the transition to infinite dome/env, and to avoid a distinguishable "reflection line" on the door panel.

Allright, where do i send the flowers, Jase? ^^

Wish I have access to Max and give Lele's sample scene a swirl.....

Err, Autodesk, i think, has a 30 day trial of their latest and greatest, pending registration.
If not, you know how to reach me, i'll go cry on friendly shoulders, and i am sure a custom timed demo could be arranged without too much of a problem.
Besides, soon enough i guess you'll have to give in to the Max side, with what's cooking these days...

[jasonhuang1115]

Allright, where do i send the flowers, Jase? ^^

Err, Autodesk, i think, has a 30 day trial of their latest and greatest, pending registration.
If not, you know how to reach me, i'll go cry on friendly shoulders, and i am sure a custom timed demo could be arranged without too much of a problem.
Besides, soon enough i guess you'll have to give in to the Max side, with what's cooking these days...

Yeah, I should definitely find some time to pick Max up as it has the latest V-Ray features cooking...The problem is I always have a long laundry list for learning and I am pretty bad at time management....

Gotta check your previous post to learn what's going on...

[LudvikKoutny]

Hehe okay:

A, Are you sure you have attached the right file? Because if I open it, all of the objects are hidden, and if i unhide them, i get output with background, not black background.

B, Check the post three post above yours. You can see me saying:

Actually, the compositing part of the workflow seems to be okay finally. Everything seems to be working right in that case. The problem I am having here is actually that workflow of rendering everything together (not comping it in post) is not working correctly now.

Yes, here I am looking for a correct way of rendering everything together. Not rendering a layer for composition.

Basically, matte/shadow workflow usually has two use cases, but in V-Ray, currently only one of them works. The one with setup for composition works flawlessly. For that, all you have to do is following:

1, Create DomeLight, put your HDRI into it and disable it's visibility

2, Put your backplate into secondary matte environment override slot

3, Make sure your environment background color is black

4, Enable matte and matte for refl/refr on your ground plane

And it will work, and it won't have the GI + DomeLight darkening bug, nor will it have the automatic projection working only for certain ray types problem. The problem I am talking about here is case where you render everything together. When you are doing lookdev, especially with client behind your back, or just building the scene, you can't just watch blank black emptiness.

And if I was to composite render with backplate in post, even if i did not lose any information (which I will), it would still just be another pointless step that could be avoided if these two problems could be fixed. I do not need any separate control over backplate and my CG objects. I don't need to color correct or transform my backplate or integrated objects separately. I usually get that right already in the renderer, with no need of fixing it in post. - That being said, having compositing workflow working correctly is also very important, so I am thankful we have that option now (with the new secondary matte environment slot). It's just that both of the workflows have their specific important use cases.

[LudvikKoutny]

Okay, so here comes the promised video

https://www.youtube.com/watch?v=VMSYerUmxx8

First 9 minutes and 30 seconds showcase the workflow in other renderers, for comparison. If you do not care about other renderers, then you may skip it, but I really strongly suggest you don't, to better get into the context and understand in which ways V-Ray falls behind

[^Lele^]

thanks, watching!

[^Lele^]

Well, mentalray behaves much similarly to V-Ray if both direct and indirect lighting are active (just it darkens in the reflections, and brightens in the direct view.).
That goes away if the skylight is turned off, losing the sharp, direct shadows.
I can't tell if you use both a dome (ie. a direct environment light) and GI in your video, with mentalray, also because the map lacks directional lighting.



Turn off the dome, lose the sharp contact direct shadows from the environment, and V-Ray will do the same thing.

Corona, likewise, doesn't use a direct light to shade your mattes (well, at least it didn't have one when i last tried.), it importance samples the max background directly (us and mR do not, atm. We will soon.), so given you're not mixing and matching projection types and ray types, it works.
Again, i'd be grateful if you could show me a scene with an HDR with a bright sun in it, so to be able to gauge the quality of the shadowing when we aren't just talking of very diffuse, contact patches (which look nigh identical with just GI and with a dome, in the case of an overcast sky.)

I suspect only Corona may be able to pull off both, at the moment, due to IS directly on the background map.

[jasonhuang1115]

Just watched it. Nice job putting all the issues together and use a simple scene to demo it again at the end. Though Max is a foreign language to me but telling from the renders I definitely experienced similar issues in Maya as well.

Similar issues were brought up in this thread here and here. I am hoping these issues got taken care for both Max and Maya users as it seems to be lingering for quite a while...

[LudvikKoutny]

Well, mentalray behaves much similarly to V-Ray if both direct and indirect lighting are active (just it darkens in the reflections, and brightens in the direct view.).
That goes away if the skylight is turned off, losing the sharp, direct shadows.
I can't tell if you use both a dome (ie. a direct environment light) and GI in your video, with mentalray, also because the map lacks directional lighting.

[ATTACH=CONFIG]27645[/ATTACH] [ATTACH=CONFIG]27646[/ATTACH]

Turn off the dome, lose the sharp contact direct shadows from the environment, and V-Ray will do the same thing.

Corona, likewise, doesn't use a direct light to shade your mattes (well, at least it didn't have one when i last tried.), it importance samples the max background directly (us and mR do not, atm. We will soon.), so given you're not mixing and matching projection types and ray types, it works.
Again, i'd be grateful if you could show me a scene with an HDR with a bright sun in it, so to be able to gauge the quality of the shadowing when we aren't just talking of very diffuse, contact patches (which look nigh identical with just GI and with a dome, in the case of an overcast sky.)

I suspect only Corona may be able to pull off both, at the moment, due to IS directly on the background map.

Sorry to sound blunt, but you probably do not know how to use mental ray. You don't have any IBL going on in there, as in MR, for IBL to be active, you also need to put in skylight light source set to "use scene environment".

It's brighter in your picture, because there are still defaults light shining in the scene. I will make you identical scene for MR, V-Ray and Corona in a moment. Just hold on

As I relied on Mental Ray to do this kind of work for several years in production, so I know what it can and can not do

EDIT: We have now have one free HDRI to use. We need also one backplate we will use, as part of the problem is specific to the HDRI+Backplate scenario, not HDRI only. I will try to figure something out

[^Lele^]

Sorry to sound blunt, but you probably do not know how to use mental ray. You don't have any IBL going on in there, as in MR, for IBL to be active, you also need to put in skylight light source set to "use scene environment".

Of course i did.
Which is why instead of black, on the diffuse sphere, you see a non-importance sampled FG mess when the skylight is off.

It's brighter in your picture, because there are still defaults light shining in the scene. I will make you identical scene for MR, V-Ray and Corona in a moment. Just hold on

Eheh, neither, i had the dome turned off, not non-existent.

To clear these up, i rotated the map around, so you will see that all that will go amiss is the contribution of the very bright, very small spot of the sun in the environment map.

As I relied on Mental Ray to do this kind of work for several years in production, so I know what it can and can not do

Feel free to peruse the links i provide in my signature: while i left it behind as soon as i could, i had to suffer the ignominy long enough, if long enough ago...
See if you find anything off the bonk with the attached file, it's quite possible as a result of the creeping old age.
Mind you, i did set it up to the best of my abilities...

EDIT: We have now have one free HDRI to use. We need also one backplate we will use, as part of the problem is specific to the HDRI+Backplate scenario, not HDRI only. I will try to figure something out

I don't think adding one more variable will make things easier on us all.
We are getting somewhere, both on the technical and the personal side, i feel (pleasantries over, i mean, we're going in the same direction. ^^), and we're close enough to get to the bottom of it, either hacking it, or requesting a change with some precision, and the least guesswork possible from Vlado and the guys.

Right at the moment, the only way out of this conundrum of wanting to both see and render the bg on mattes with both GI and Dome would be to get rid of the dome entirely, as the IS for the HDR map would be done automatically for the backdrop slot.
With BF as primary, you'd get as good shadows as any, without the mind-boggling projection and ray type mix.
Mind you, i'll change my mind a few times before this will be over... ^^

[LudvikKoutny]

Ah, I apologize. But still believe you did something wrong in your MR setup. Anyway, let's consider this our standardized testing scene: https://dl.dropboxusercontent.com/u/...MatteScene.zip

It has one backplate and one matching HDRI with strong sunlight. No variables here.

I've tested it in all 3 renderers:

Corona:


Mental Ray:


V-Ray:


While Corona and MR are very consistent, V-Ray seems to do something odd. Aside from the matte darkening bug, there seems to be also something odd going on with projection in refraction, and self illuminated material seems to emit significantly more light than it should. Multiplier of self illumination in all 3 scenes is set to same - 1 image unit, and none of the scene contains any exposure control/tone mapping.

But mainly, this is a nice example that V-Ray is only renderer that currently can not do this simple thing without issue.

[LudvikKoutny]

Okay, and regarding your MR scene, you have indeed made a few mistakes:

1, By default, MR's matte material has slightly transparent shadows. This is due to the enabled AO. MR's defaults are still in 90's, so first thing you have to do is this:


2, You have enabled "receive direct illumination" checkbox. That is wrong. That checkbox is for special light source types called illuminators. Illuminators are light sources that were not present in footage/backplate at the time it was being captured. It's for example when you add car with headlights into a night shot. Headlights were not there at the time of photographing the plate, so renderer needs to know to not use those lights to reproduce already present lighting scenario, but to add them to the scene. By enabling that checkbox and not using include list below, you made your skylight light source illuminator, effectively doubling the amount of light on matte material.


3, Your sphere does not glow because you forgot to enable FG visibility of self illumination:


After that, i just enabled IBL and Skylight, and everything was nice and dandy:


Here's also fixed scene for you
BackplateSetup-mr_fixed.zip

[^Lele^]

Also, i just checked in Corona.

There is a fair warning on the alpha channel for the matte material: if i want also the shadows in the alpha ("for compositing") i am told to make the Background Black.
As ofc it can't to do both things at the same time, and darkens the plane in the direct rays.
So, in corona, if i want the plane to behave as you say, i am stuck to the render, as the matte's alpha will be solid.
If i want the shadows to be the matte object's alpha, i have to do precisely like i did in V-Ray: make it all black. go on to be a happy Comper.

See in the attached contact sheet the top row being "always solid", and the bottom being "for compositing".


Notice this type of behavior can be mimicked in V-Ray quite precisely, with a mix of the stuff i posted here in the thread.
Simply turn off "receive GI" and the vray plane will catch the direct shadows without darkening up.
Just like in corona (it turns the shader pitch black: tantamount to.), however, you lose the ability to light the environment projected mattes.
For V-Ray to behave as corona in composite Mode, you need to deactivate the environment backdrop map (ie. black), and make sure your dome is visible to provide for a BG for the direct rays.
And then turn back on receive GI on the matte.

Example of it in Vray:



What gives, then?

[LudvikKoutny]

Ehhh... I am a bit confused now...

First of all, to make BG black in Corona to set it up for compositing - once you set shadowcatcher mode for compositing, just go to render settings, and in Scene tab, under environment rollout, just enable direct visibility override, and leave it black - tadaaaa, you have your pass ready for compositing.

That being said, how is that even relevant to this thread? This thread is about an issue of V-Ray currently not being able to correctly handle Backplate integration in case of rendering everything together in one pass. It is not dedicated to searching for problems in other renderers, nor is it dedicated to the workflow of rendering mattes on black background for compositing. I am interested in how to get correct results in one pass, without need of compositing, and how to do it in V-ray

Edit: I would also suggest you use the scene I have prepared two pages back, one on wooden table, so we can have one unified scene we both try our examples on That scene is also correctly set up for both MR and Corona, so you can do fair comparisons.

Edit 2: The point it is that way in Corona is that when you render on a backplate directly, you don't have much use for alpha, since you can't comp it correctly as it was not rendered on black background. If V-Ray would work correctly with the "render everything in one pass" workflow, I could not care less about how alpha looks. That matters only when you render on black for compositing.

[^Lele^]

Okay, and regarding your MR scene, you have indeed made a few mistakes:

1, By default, MR's matte material has slightly transparent shadows. This is due to the enabled AO. MR's defaults are still in 90's, so first thing you have to do is this:
[ATTACH=CONFIG]27652[/ATTACH]

I had AO manually disabled in my scene, from the moment i created the shader.
I further reopened the packed scene, same thing.
No matter either way.

2, You have enabled "receive direct illumination" checkbox. That is wrong. That checkbox is for special light source types called illuminators. Illuminators are light sources that were not present in footage/backplate at the time it was being captured. It's for example when you add car with headlights into a night shot. Headlights were not there at the time of photographing the plate, so renderer needs to know to not use those lights to reproduce already present lighting scenario, but to add them to the scene. By enabling that checkbox and not using include list below, you made your skylight light source illuminator, effectively doubling the amount of light on matte material.

I had it enabled because you required me to have both direct lighting and GI lights lighting the mattes.
This isn't trivial a point, and rather the whole crux of the matter, which i have been beating upon like a mordor blacksmith for the past two days: you can not mix and match as you please, but should take great care when matting.
Cfr the autodesk manual on the matte material:

http://help.autodesk.com/view/3DSMAX...2-A96A0880CF84

[B]Direct Illumination rollout[/B]

[COLOR=#333333][FONT=Arial][COLOR=#333388]Note:[/COLOR] The lights specified on this rollout actually illuminate the background, unlike [URL="http://help.autodesk.com/cloudhelp/2016/ENU/3DSMax/files/GUID-3F934E37-CC74-4EC7-A0E2-A96A0880CF84.htm#GUID-3F934E37-CC74-4EC7-A0E2-A96A0880CF84__WS73099CC142F487553B93539F117EA10CE8F-DE3"]shadow-casting lights[/URL]. [B]Thus, for the effect to be correct, make sure no light source exists in both lists.[/B][/FONT][/COLOR]
[COLOR=#333333][FONT=Arial]
[/FONT][/COLOR][COLOR=#333333][FONT=Arial]Receive Direct Illumination: When on, the surface renders where struck by direct illumination. Default=off.
[B]If Illuminating Lights List is off, all lights in the scene illuminate the surface.[/B][/FONT][/COLOR]

The bolding is mine, for readability.
Which is precisely what is happening which shouldn't, in V-Ray and mR, and Corona under the same conditions.

3, Your sphere does not glow because you forgot to enable FG visibility of self illumination:

That is correct, my mistake there.
You will notice nothing in fact changes: we just can't have both.

After that, i just enabled IBL and Skylight, and everything was nice and dandy:


Here's also fixed scene for you
[ATTACH]27656[/ATTACH]

It isn't fixed at all, unfortunately.
It works precisely like V-Ray and Corona.
And Renderman, and Arnold, and iRay.

here, the render from your scene (opened, pressed render, screenshotted.):


I think i proved my point quite largely and quite inescapably, blunt for blunt, and in any event i would not really know how to add more to the discussion, by now.
Maybe, as i pointed out, having the IS done in the background slot could solve the issue by not mixing ray types, but who knows, in corona it doesn't, for example.

• You want V-Ray render with your backplate, you have the setup with the alpha unusable but no darkening.
• You want to composite it , you have the setup to render it on black with the correct alpha.
• You want both, no one on the planet has it, as far as i know.

Surely not the ones you claimed were "ages ahead" in terms of workflow: mR is horrible, Corona simplistic, still, and in any event neither does what you claim V-Ray should do to be at least on par with them.

[LudvikKoutny]

Come on man, really?

Two pages ago, you were showing me mental ray scene telling me mental ray has same problem of the matte object creating visible outline. I fixed that and now you fixate on alpha? As I said, if the workflow works and does not darken anything, I could not care less about alpha looks. If you have solution that does work with domelight, does not darken the matte objects, keeps GI working in all aspects and does not introduce any splotchy artifacts around contact area, then please send me the scene example. I haven't seen any working example from you so far.



In this post: http://forums.chaosgroup.com/showthr...765#post675765

You can see same scene rendered in both MR and Corona, doing exactly what I claim it to do. Render everything together in one pass, with Correct GI, correct projection, and no weird darkening or outlines of ground plane. With V-Ray, you can not. You have to either sacrifice GI on the matte object, or using high contrast HDRI. The claim is backed up with a file containing all 3 scenes.