- [Instructor] Let's go a bit deeper
into the physical material parameters
and see how to control reflections.
I'll create a material in the slate material editor,
right click in the view, choose materials,
general, physical material.
And let's double click on the sample swatch here.
We can also minimize the material,
just make it a swatch only.
Let's choose a preset from the pull down list.
We'll go down into metals
and let's go for silver.
Choose the silver preset
and then we want to change the material mode over
to Autodesk standard surface compliant.
Now our preview here looks a little bit strange.
It looks almost transparent.
Actually, what's happening is it's reflecting the background
and that background is just a solid gray.
We can substitute a checkered background.
Right click on that sample.
From that popup menu, choose show background in preview.
And now we see a checkered background and we see a sphere
that's almost perfectly reflecting that background.
In order to really see what we're doing,
we need to have a proper model with some proper lighting
and I've got that set up already.
We can just launch the active shade window.
Click on active shade on the main toolbar.
And I've set that with a very small preview
so that we'll get faster updates.
Let's go back to our material
and make some more adjustments.
Let's assign our material to the tabletop.
Click on the output of that material,
drag over to the tabletop in the 3D view
and now we see we've got a silver preset assigned there.
And we get very shiny highlights.
They're not perfectly shiny.
It's still a little bit fuzzy.
We could give this the effect
of a perfect first surface mirror
that was absolutely smooth
and to do that,
we would give it a reflection roughness of zero.
We'll just type in a zero there, press enter.
Now we have perfectly sharp mirror reflections.
Notice that the material sample did not update
and in fact, it just went away.
The Max 2A plugin only allows one rendering at a time.
To render both active shade
and the material editor sample at the same time,
you need to pay extra for a full license
of the Arnold base package.
Let's talk about metalness.
That's what's giving us this silver effect.
We see under reflections, there's a metalness parameter
and it ranges from zero to one.
It fades between two different shading models,
metallic and non metallic.
If I bring this back down to zero,
we see we're getting a bright material here
with shiny highlights, but it doesn't look like silver.
We can bring metalness back up to one
and we've fully enabled metalness.
With a high metalness,
the color of the reflections will be strongly influenced
by the base color of the material.
Let's adjust that.
We'll click on the base color swatch
and in the color selector, let's set the hue to 0.1,
press tab and set the saturation to one
and press tab and also set the value to its maximum of one
and now we have a gold tabletop instead of a silver one.
Let's set our base color reflections back to what we had.
We'll bring the saturation back down to zero
and click okay.
Let's explore some of the possibilities with reflections.
We've got currently, a base color of white
in order to see the reflections more clearly.
Let's bring the base color weight down to zero
and now we get dimmed metallic reflections.
And that is going to be influenced
by the reflection roughness over here.
With a roughness of zero, we have shiny sharp reflections.
If we increase the reflection roughness
up to its maximum of one,
then we actually still get some reflections.
They're just really scattered.
We don't have a perfectly black surface here
and we could try to reduce the reflection amount
but that will only work
if the metalness value is not set to one.
And we could try to dim down the reflections
by adjusting the reflection weight over here,
but because the metalness is set to one,
that is actually disabled currently.
Let's look at non-metallic reflections.
We'll bring the metalness parameter down
to the minimum of zero.
And now in our active shade,
we see that the reflections are even more diffused.
But now we have the ability to adjust the reflection weight.
So we can bring that down to zero
and now we have a perfectly black rendering
because we have no base color, no reflections
and in fact, no other shading component.
All the weights are set to zero now.
Now technically, reducing the reflection weight
is a non physically accurate technique
but it is extremely useful for art directing materials.
Let's talk about the sort of proper,
more physically accurate way to adjust reflections.
We'll bring the reflection weight back up to one.
We'll set the reflection roughness down to zero
so we can really see it very clearly.
And for non metals, the spread of reflections
is controlled by high OR, or index of refraction.
That's the density of the material
and as the name indicates,
it also applies to transmission or light refracting
as it travels through a material.
A high index of refraction is going to bend light more
when it passes through or bounces off a surface.
With a low IOR, if we bring this down,
we will only get reflections on the edges of objects
where the surface is more perpendicular
to the camera's line of sight.
With a high IOR, the reflections will spread out more.
We'll get stronger reflections in areas
where the surface is more parallel
to the camera's line of sight.
Physically plausible values will range from one,
which is the density of air,
up to an IOR of about 2.4, which is the density of diamond.
But the IOR field
lets you plug in non physically accurate values
just as the reflection weight does.
So we can take our IOR above 2.4.
It's not going to have a lot of effect in this particular case.
We can also bring IOR down below one
and when we bring that down into fractional values,
we get extremely hot highlights
that are not physically possible
but they may be just what you need in your rendering.
All right, that's an overview of the reflection parameters
for the physical material.