Vray versus Mental Ray Interior scene

[paraganek]

First of all thank you all guys for a lot of helpfull information and testing in the previous Vray versus Mental Ray Exterior scene topic.
As many of you have suggested, an interior scene is going to be the only real test between those two renderers.

I have just started using one older simple interior scene and here we go:

One exterior Direct Light (Sun), Skylight and 2 Spot lights in the kitchen.
There is not much to tweak in the vray setup I guess, it is pretty straightforward: IR map for primaries, Light Cache for secondaries, the first one is set to HSV Exponential Color mapping.

[img]ftp://visitor:newlands@ftp.newlands.cc/mr/vray_int_01.JPG[/img]

The same with Linear Color mapping:
[img]ftp://visitor:newlands@ftp.newlands.cc/mr/vray_int_02.JPG[/img]

Mental Ray:
[img]ftp://visitor:newlands@ftp.newlands.cc/mr/mr_int_01.JPG[/img]

The image still has many bad splotchy areas and the render time is already higher than the vray one. I am trying to get rid of these without sacrificing the render time now. This is the current setting:
[img]ftp://visitor:newlands@ftp.newlands.cc/mr/mr_int_01_setup.JPG[/img]
Any suggestions welcome

[Morbid Angel]

well your final gather samples are way low. try increasing those or working with radii in pixels or radius.

[paraganek]

well your final gather samples are way low. try increasing those or working with radii in pixels or radius.

Well OK. Final gather is going higher so to compensate for the longer render time I had to reduce the number of photons this time.

[img]ftp://visitor:newlands@ftp.newlands.cc/mr/mr_int_02.jpg[/img]

It definitely helps but the render time goes up again and I am trying to stay below 4 minutes on my machine (or even better - to beat the vray time :P ).
I have posted a thread in the Mental Ray forum so we will see if someone comes with an idea.

[percydaman]

I dont think your going to find alot of mental ray experts here. Try www.cgtalk.com or another less centric rendering forum.

[paraganek]

By the way, if someone wants to play with the Vray scene to get maybe even faster render time, then here is the scene

Vray, Max7, maps included

Mental Ray, Max7, maps included

So far, Vray seems to have jumped out to a bit of a lead. I wonder if it is somehow possible for Mental Ray to come closer in both speed and quality in this scene.

[paraganek]

I dont think your going to find alot of mental ray experts here.

You are absolutely right Percy
When I get some advices from Mental Ray community (if ever ) hopefully the Mental Ray scene will render in a snap then and I can come back here and challenge some of you to take the vray setup and tweak it to beat the Mental Ray time ! How does that sound ? :P

[paraganek]

Well I have been tweaking the Mental Ray scene and got some nice clean image rendered really fast.
I have also optimized the Vray scene (switching all materials into vray ones, tweaking IRmap and light Cache) and rendered a new image.
Both engines now render in close enough times so I am posting both images for you to compare the differences.

[img]ftp://visitor:newlands@ftp.newlands.cc/mr/mr_int_03.jpg[/img]

[img]ftp://visitor:newlands@ftp.newlands.cc/mr/vray_int_03.jpg[/img]

I personally like the Mental Ray render better, it has nice shadowing in some areas (darker wall behind the kitchen block, shadows from the fridge handles) and the overall atmosphere feel warmer (closer to a real sunlight).
If anyone has any ideas how to render the vray scene to match the mental ray render close please share.[/img]

[Sawyer]

Is it possible to share the file (vray only)

Thanks

[paraganek]

Is it possible to share the file (vray only)

Check my post from Tue Jan 17, 2006 9:15 pm, there is a link.

[vlado]

The mental ray image has some light leaks in corners caused by too little photons in the photon map. Also, it has too few light bounces for a scene like this - adding more bounces would change the result significantly. The direct sunlight also appears stronger in the mental ray image. Anyways, I will play with this tomorrow...

Best regards,
Vlado

[Sawyer]

Here is what I have:

This images uses gamma correction 1 - .4545. I increased the lights by about 4-5x and used inv sq. falloff. I also have the sunlight ussing area shadows - 4" size. I tweaked the kitchen light color.
Also the falloff you have for the kichen lights is really huge.
I changed to the preset low setting for the irr map and put subs and samples down to 20. And it's really too low you need to up these settings but it's a nice time for a preview.

The only thing I changed on the mats was that the refraction subs were set to 50 I placed it at 8.

Rendering took me 1min 40s

[Sawyer]

This image is using the high irr map preset and 30/30 subs/samples. There is a lot more shadow detail.

This rendered at 5:13.

[Morbid Angel]

guys, now we all know that the right amount of photons and fg/lc gi can produce a reletevly close render times in both engines, however now try applying some effects to the scene like glossy reflections to the floor for example, use displacement, turn on motion blur or dof....good luck mental ray

[Da_elf]

good luck to the computer rendering, hopefully it wont fry the motherboard and chips

[vlado]

A bit late, but here are my attempts at this scene.

Some notes:

(*) I used max8, since the mental ray version that comes with it seems to do a better job at FG, and FG is essential for this image. Further on, mental ray in max8 supports multibounce FG, which is also essential for a correct result.

(*) Since photon-mapped GI in mental ray does not work with skylight, you cannot use it in this scene. Using it will not produce a correct image, as it will be lacking a major component in the lighting. Apparently, this seems to be a common mistake when using mental ray. To make up for the missing lighting, you have to use area lights at the windows, but settings them up in mental ray is complicated and I didn't do that.

This puts mental ray at a disadvantage for this scene, as you have to use multibounce FG to get correct lighting, which is slow with many bounces. And to get the lighting more or less correct for this scene, you *do* need a lot of bounces, as shown in the images below. Of course, you can resort to some fakes so that you can use photon-mapped GI after all (e.g. adding an additional blue omni light or similar), but I didn't do that either.

In V-Ray, you can use the light cache to get the secondary lighting correct and fast, and it does account for the skylight. Further on, similar to radiosity methods, the light cache does not place a limit on the number of light bounces. What you get is the correct final lighting distribution in the scene. At present, there is no comparable indirect illumination method in mental ray, as both photon mapped GI and final gather are limited in the number of bounces they account for. Of course, you can get results that are sufficiently close to the correct solution, but this takes additional time.

Here is an image of mental ray rendering with GI, without the sun, to demonstrate better the fact that GI alone does not account for skylight:

full-res image: http://www.spot3d.com/vray/images/st..._gi_no_sun.png

Here is a series of renderings with different number of bounces for final gather; as you can see, more bounces (more than 1 at any rate) drastically change the result. I have disabled the sunlight to better demonstrate the effect of skylight:

full-res images: http://www.spot3d.com/vray/images/st...no_sun_all.png

Here is a series of similar images done with V-Ray. As you can see, render times are pretty similar, although the result in V-Ray is a little more detailed. In the last image, the light cache accelerates the rendering a lot, plus it gives you the total correct solution:

full-res images: http://www.spot3d.com/vray/images/st...no_sun_all.png

Here I have enabled the sun and re-rendered:

full-res images: http://www.spot3d.com/vray/images/st..._mr/finals.png

The results for both a pretty similar, but the light cache gives V-Ray a distinct advantage with respect to rendering speed.

Best regards,
Vlado