Multi-region rendering

[TheLooopCGI]

I can't really tell you why but if you render and compare two images: once rendered normally and second time with everything matte except the object of interest you will see a difference. It can be only subtle or very different, depending on the scene.

I made a simple test render and attached comparison pictures below. The scene is a ball enclosed in a small "room" created by 4 planes. The light is emitted by a very bright vray light on the left. You can see a big difference between the ball that is rendered normally and the ball that is enclosed by matte planes.



Instead of making the objects matte I'd better make them invisible to camera. The light also changes but it's almost unrecognizable.

[glorybound]

The benchmark scene, that I posted (http://www.chaosgroup.com/forums/vbu...ight=benchmark) requires you to select the items you want to render. I think this is a plug-in, or maybe it's part of MAX, but wouldn't it accomplish what you are asking?

[TheLooopCGI]

glorybound, I downloaded the scene you mentioned but the only plugin there is the greeble plugin. It's only for those paneling details on the walls.

3dsmax has some options to render only selected parts but it only makes one large region that encompasses the selected objects. It won't create several small regions that would contain only the selected objects.

[vlado]

I think you need something like the ability to render only the pixels of the selected object(s), rather than multiple regions, is that correct?

Best regards,
Vlado

[TheLooopCGI]

Ah, Vlado! You're alive!

Nooo, this is something that cubiclegangster would love so he can have exactly his layers, but the problem with exchanging objects is that the light on the surrounding objects gets influenced by them. So we really need a region - big enough to include the whole change. Sometimes smaller, sometimes bigger, depending on the position and color of the surrounding objects. Having only the exact pixels of the selected object is not enough unfortunately.

I was thinking that since the ability to render a region in VFB is already there then implementing multiple region ability should be relatively easy, no?

[TheLooopCGI]

Seems like my enthusiasm was premature...

[trixian]

Are you looking for features like in this product?
They let you separate your object in passes but include the gi from it so for example changing the texture\colour of an object changes its GI in the rest of the scene as well.

[TheLooopCGI]

Wow! Thanks a lot for the tip Christian!

It's exactly the type of work we often do so I'll definitely look into it. Of course there's always a question of what it can or can't do. Multi-region rendering is primitive in comparison to Calimo but you don't have any limitations, it's bundled (or could be ) with V-Ray and it solves the situation when you have several mistakes on your picture that you just want to re-render and don't want to baby-sit the rendering of each region.

[Swahn_Kung]

One easy workaround is to create a flat spline object (a rectangle) and create one or more holes in it.
Orient the object towards the camera and place it in between the camera and the rest of the scene.
Use Face Extrude modifier on the spline object to make a surface out of it.
Make the object a Vray matte object (Alpha contribution -1,0) and animate the splines that make out the holes as needed.

This way you can emulate render region, but with multiple regions as well as the ability to animate them it terms of size and shape. Just link the spline object to the camera and you are free to move it around without messing up your render regions. It helps to create a grid object, align and link it to the spline object in case you want to create more regions or move existing ones.

I'm sure it wouldn't be that hard to make a macro script that allows one to quickly create this with just a button.
I've used this on several scenes when I only needed to render a small moving object but needed a projection culling rather than a volume culler (such as VraySpereFade.)

[TheLooopCGI]

Or make it easier and just create a small black plane very close to the camera, oriented toward it and cut holes in it with a cut tool.

Unfortunately it still doesn't solve the problem of keeping the image intact outside of render regions. All these ideas you guys presented overwrites the entire image.

[Swahn_Kung]

But using a compositing tool might help you though?

If you render out linear material it's quite easy to just overlay a "render region render" on top of a previous full-sized render. You won't get the direct feedback you perhaps seek in the frame buffer though.

[TheLooopCGI]

It's exactly what we discussed with cubiclegangster already.

You might say that my request for multi-region rendering is exactly for the purpose of not needing to use Photoshop when I just need to render several regions of a picture.

[Swahn_Kung]

My apologies
I guess I have no solution to your problem then.

[JohnVK]

+1 for multi-region render options

I would really find a multi-region rendering option VERY usefull as well! It happens many, many times that I simply want to render multiple parts or "L-shaped parts" of the entire image anew. Indeed it would be great if that could be done from within 3ds Max/VRay in one go without the need for alternative methods or having to render those seperate parts manually (and losing the previously selected region selection rectangle in the process).

[Micha]

Any news from a multi-region-feature? Often missed here too.