- [Instructor] Texture maps are positioned
onto geometry using a uv coordinate system
that maps each part of the texture map
to a particular vertex.
Default uv coordinates are assigned to the vertices
when the geometry is created and projecting texture maps
actually edits those original uv coordinates.
So here's a texture map.
And the uv coordinate structure puts zero-zero
down in the lower left hand corner.
In other words, a vertex that has a uv coordinate
of zero-zero will be getting this pixel right there.
This would be one comma zero.
One comma one.
Zero comma one.
The pixels right here in the center would be 0.5 in u
and 0.5 in v.
Now those numbers aren't tied to the map itself.
They're tied to the geometry like this.
So I'll cut this here.
Turn that on.
Push in.
I'm going to set the display to a wire frame
'cause we're going to be looking at the vertices
of this guy here.
I'm also going to turn off the grid.
Let's push into this corner here
so we can see our vertices really close.
There we are.
Nice dramatic angle, right?
Okay, cursor in the viewer, type S to get
the project settings for the viewer.
Switching to 3D, these now control what I can show
of my geometry.
For example, this says show me all my vertices.
There they are.
This says show me the numbers of the vertices.
Zero one two, so on and so forth.
Turn that off.
This shows the uv coordinates for the vertices.
And as you can see, the lower left hand corner here is
zero comma zero.
Moving to the right, in u, 0.12, and in v, zero.
So there are the uv coordinates, again,
assigned to the geometry.
So if I project a texture map onto this,
I'm really editing those numbers on the geometry like this.
Let me bring up my uv, let me push in here to this guy.
Okay, so we've got the uv project node up here.
And right now, the projection is turned off.
But if I decide to turn it on to something like
a planar projection, watch my uv coordinates
on the geometry.
Bang, they all snapped!
So, we are in fact, editing the uv coordinates
on the geometry.
That's what uv projection does.
And if I turn it off, I'm going to get my original coordinates.
Okay, so let's reset this viewer.
And I'm going to turn off all my funny screen displays.
Turn my grid back on.
Okay, we're done with this.
So I'm going to turn that off.
We'll cruise over here and turn this on to look
at this setup here.
What we're going to do is look at the perspective projection.
I'll open up this uv project node.
It's set for perspective.
Now perspective means you have to have a camera attached.
And the camera, it's exactly like shining
a slide projector on top of any surface.
So if I select the camera and I were to do something
like move the camera closer or further,
or if I were to tilt the camera up or down,
so that is going to affect the projection.
I could also, let me swing around the side here,
come to the lens focal length,
and if I widen the lens, it's going to cover more
of the geometry.
If I lengthen the lens, it'll cover less.
So the camera is what controls the projection
in the perspective node of the uv project node.
Okay, let's take a look at the Project On feature.
This only pertains again to perspective projection.
Project On has three options.
Both the front and the back side of the geometry,
or the front only, or the back only.
Now here's the bafflement, if I say project on the front,
I'm still getting some stuff back here.
It is doing a perspective projection on the front
so what's going on back here?
What's going on back there is it's not editing
any of the uv coordinates on that side of the geometry.
There's still the original default.
I can prove that to you by turning the projection off.
The back side didn't change at all.
We turn it back to perspective,
and the front gets the perspective coordinates
but not the back.
And if we say show me the back,
that means only the back side will get the projection
and the front side's going to get the original default.
That's not exactly the way I would have it work,
but that's the way it works in Nuke.
Okay, let's turn this off, and go look at some
more general cases.
And we'll turn this on, and take a look at this.
So what's going on here?
I'll open up this uv project node.
And I've got some geometry here.
This is none of the geometric primitives of course.
This is an actual regular piece of geometry.
And he seems to only have his pants on.
In the next video, we'll take a closer look
at how planar projection works.