- [Instructor] Multi-pass rendering is a technique
that allows you to easily make changes in post.
And once you've rendered out an image in multiple passes,
you can then adjust things like your reflection, refraction,
or even the relative values
of different lights in your scene.
Now, let's go ahead and set up our project
for multi-pass rendering.
So in the render settings,
we're going to turn on multi-pass.
And you can see in the save dialogue here
that we have multi-pass image available to us now.
There's similar settings to the regular image.
We can choose a file format, a bit depth,
and save it using tokens or whatever we prefer.
Now you can add passes
by pressing the multi-pass button here.
But what passes do you need?
Well, if your goal is ultimate control over the beauty pass,
you can choose all the passes
that make up the flattened image.
Now, knowing which ones they are can be difficult initially,
but a good tip is to look at your materials.
So first we're going to look at the logo material,
and we've got luminance.
We have some color, but luminance is going to override that.
We also have reflectance as well.
And so what we can do, then, is choose some passes
which will help us to build up that image.
Reflection is obvious,
and ambient is what we'd need for the luminance.
Now, let's check what kind of lighting we have in our scene.
Let's close down the render settings.
Look at the lighting.
So all volumetric lighting.
Well, let's come back to our render settings,
and we'll choose to add the atmosphere pass.
Now, I'm going to add the ambient occlusion effect.
And I also want to control that in post,
so I'll come over to multi-pass
and choose to add ambient occlusion.
Finally, I'll add special passes,
like motion vector
and depth.
And then I'm going to check through the scene,
and I'll add any object buffers.
Close down the render settings.
Twirl open my objects, and I can see I've got a couple of
compositing tags here.
If I just look through the rest of the scene.
Yep, there's another one.
I need to enable object buffer one, two,
three, and four.
And so I'll do that by coming over to multi-pass
and choosing object buffer here.
Now you can see the group ID is set to one.
If I add another one, it stays on one.
It doesn't count up.
So you do have to manually input these.
It's not automated.
So there we go.
We've got object buffer one, two, three, and four.
So when we come to save this,
we don't necessarily need to have the regular image anymore.
We could come over to our multi-pass
and just use RGBA image,
and that would give us essentially the same thing.
So I'm going to output just a single frame, current frame.
And let's just scrub through to somewhere around here.
And I'm not going to save this.
I'll just view it in the picture viewer.
One thing to note is,
especially if you're using motion vector and depth,
you want to make sure your depth of your images
are 16 bit or greater so that you've got that information
there to use in post.
So I'm going to render this now to the picture viewer,
and we won't see any effects like depth of field
because, of course, we're adding that in post.
We're just using the depth pass to get that information,
and you can see, if I go to single-pass mode,
there's the information in our depth pass.
There's the information in motion vector.
This is the background image or the RGBA.
And, if I turn off motion vector and turn on multi-pass,
we can see it's exactly the same as the flattened image.
Now we can be sure that we have all the right passes here.
So we can step through.
We've got the atmosphere, reflection, ambient occlusion,
the ambient pass, and all our other ones
including our object buffer which has all our objects in,
and then we're isolating certain elements.
So the picture viewer is really cool, really useful.
If you've never used multi-pass rendering before,
it even shows you how you should composite the layers
and the blending modes.
And of course, we can
adjust them right here.
So that just shows how flexible this system
and way of rendering is.
And so, by taking the passes into a compositing program,
you can really tailor the look of the final output.
So that's how we'd set up a multi-pass render in Cinema 4D.
By separating the passes, we have more control in post.