OK.

So welcome for the last lecture of computer graphics this year.

And today we want to finish the modeling chapter.

And last time, what I described were data structures

to store polygon or triangle meshes.

And we saw different representations

that some are very simple and just sufficient for rendering.

Others are more complicated but allow you to traverse

and to iterate over triangles and stuff like that.

So that's the most common way polygon meshes

to represent single objects in computer graphics.

There are other methods.

I already mentioned these.

So things like parametric surfaces, splines,

or NURB surfaces.

I won't detail on this here in this lecture.

This is done in detail in geometric modeling.

Then there is constructive solid geometry,

which means computing with objects, computing unions,

subtractions, and so on on objects

to construct new models.

We won't speak on that.

Subdivision surfaces is also a sort

of variant of parametric surfaces

and procedural models, really models

that generate geometry that accept a number of parameters

and then a tree or something is generated.

But most of these for rendering are

transformed to polygonal meshes.

And these are then rendered.

So this is really the basic common denominator

for rendering polygonal meshes.

But nevertheless, these meshes typically only

describe single objects.

So we can describe a table, a computer, a projector,

whatever.

But on top of this, typically models

are still combined to generate an entire scene.

And this is what we want to speak about today.

That's what we call hierarchical modeling.

Or this modeling is typically done in a hierarchical manner.

That's the obvious way to arrange objects.

And this is what we are going to speak about today.

So as a simple example, let's take

the modeling of the mensa.

I think most of you know the mensa.

So first of all, of course, we have the building parts.

That's walls around, windows, the floor, ceiling,

and stuff like that.

So that's the building itself.