[solved] Is there any way to exclude a part of image from the iray render?

drinformation

I wonder if there is any way to add a mask or something and pervent iray from rendering a part of image?
there are part of image that are not important and it would be awesome of we could make iray skip those parts and spend the render time on the more important part. is that possible?

prixat

Are you asking about making part of the image transparent?

drinformation

no, though if we exclude parts of images those parts will remain transparent but what I want to do is perventing iray from spending lots of time on less important parts of the image it's rendering and make it render the only parts that are important to me.
like rendering only half of the face, the eye on the other side and some of the hair. leaving the rest blank

barbult

Iray Section Plane will do that for you.

drinformation

section plane is a handy tool but I'm afraid it adds to amount of render I'll have to do, what I want to do is re-render those grainy parts of my previous render that never clear and add it over in post. there should be a way to tell the render engine to leave the out of depth part of image alone and focus on the shady part of the face.
there is this tool that allows us to mark certain pixels as finished so Iray ignores them but unfortunately it exist only in my head...

Tobor

You can achieve *some* of this with light path expressions, but be forewarned this feature is not well documented, and you'll need to do considerable trial-and-error to get the effect you want. You can find some threads about it here. As it's a standard Iray feature, you can also look for non-D|S discussions at other sites.

In the end, however, using LPEs doesn't dramatically cut down on rendering time. Its intended purpose is to allow easier compositing of multiple rendered images, so you can adjust the output in post.

Unlike some renderers (like Lux), Iray doesn't have a feature to "paint" over pixels you want the engine to concentrate on, or conversely, ignore. It would actually be a nice feature. If Iray supports it internally, at present D|S lacks the user interface to take advantage of it.

Richard Haseltine

You could use the Spot Render tool, setting it to render to a new window in the Tool Settings pane.

drinformation

@Tobor, I've looked into LPE before and it didn't look to be any help.
oh and I didn't know there are render engines that do that, guess my brain wasn't the only one thinking of that...

@Richard, that's exactly what I needed, I just wasn't sure if it's possible since my tool setting panel is always hidden and I never seen the options ^_^

Tobor

When you use a canvas and nodes to render specific items you're really using LPEs. The expressions are just done "under the hood" for you. Using a Beauty canvas and selecting the nodes (objects) to render is a good way to learn how to use this feature.

It all depends on what the "most important part" means. Depending on the scene and its components, node selection alone is one method of hiding an object but still having it influence the scene (e.g. shadows). With that, you could combine scene elements in post and still have something realistic to work from. Simply hiding an object can make for unrealistic renders.

Spot renders are useful but they can be hard to control so the various spots you might create can be seemlessly combined.