TouchDesigner | The Underlying Geometry

One of the benefits of working with TouchDesigner is the ability to work in 3D. 3D objects are in the family of operators called SOPs – Surface Operators. One of the aesthetic directions that I wanted to explore was the feeling of looking into a long box. The world inside of this box would be characterized by examining artifacts as either particles or waves with a vaguely dual-slit kind of suggestion. With that as a starting point I headed into making the container for these worlds of particles and waves.

Before making any 3D content it’s important to know how TouchDesigner processes these objects in order to display them. On their own, Surface Operators can’t be displayed as a rendered texture. In TouchDesigner’s idiom textures are two-dimension surfaces, and it follows that the objects that live in that category are called TOPs, Texture Operators. Operators from different families can’t be directly connected with patch chords. In order to pass the information from a SOP to a TOP one must use a TOP called a Render. The Render TOP must be connected to three COMPs (Compositions) in order to create an image that can be displayed. The render TOP requires a Geometry COMP (something to be rendered), a Light COMP (something to illuminate the scene), and a Camera COMP (the perspective from which the object is to rendered). In this respect TD pulls from conventions familiar to anyone who has worked with Adobe’s After Effects.

Knowing the component pieces required in order to successfully render a 3D object it’s easier to understand how I started to create the underlying geometry. The Geometry COMP is essentially a container object (with some special attributes) that holds the SOPs responsible for passing a surface to the Render TOP. The default Geometry COMP contains a torus as a geometry.

We can learn a little about how the COMP is working by taking a look inside of the Geometry object.

Here the things to pay close attention to are the two flags on the torus object. You’ll notice in the bottom right corner there is a purple and a blue circle that are illuminated. The purple circle is a “Render Flag” and tells TouchDesigner to render the object, and the blue circle is a “Display Flag” which tells TouchDesigner that this is the object that should be displayed in the Geometry COMP.

Let’s take a look at the network that I created.

Now let’s dissect how my geometry network is actually working. At first glance we can see that multiple objects are being combined into a single piece of geometry that’s ultimately being passed out of this Geometry COMP.

If we look closer we’ll see that here that the SOP network looks like this:

Grid – Noise – Transform – Alpha Noise (here the bypass flag is turned on)

Grid creates a plane that’s created out of polygons. This is different from a rectangle that’s only composed four points. In order to create a surface that can deform I needed a SOP points in the middle of it. The grid is attached to a Noise SOP that’s animating the surface. Noise is attached to a transform SOP that allows me to change the position of this individual plane. The last stop in this chain is another Noise SOP. Originally I was experimenting with varying the transparency of the surface. Ultimately, I decided to move away from this look. Rather than cutting this out of the chain, I simply turned on the Bypass Flag which turns off this single SOP. This whole chain is repeated eight times (for a total of eight grids).

These Nine planes are then connected so that the rest of the network looks like this:

Merge – Transform – Facet – Texture – Null – Out

Merge takes all of the inputs and puts them together into a single piece of geometry. Transform allows me to move object as a whole in space. Facet is a handy operator that allows you to compute the normals’ of a geometry, which is useful for creating some more dynamic shading. Texture was useful for another direction that I was exploring, ultimately ended up turning on the bypass flag for this SOP. A null, like in other environments, is really just a place holder kind of object. In the idiomatic structure of TouchDesigner, the Null is operationally an object that one places at the end of operation string. This is considered a best practice for a number of reasons. High on the list of reasons to end a string in a Null is because this allows easy access for making changes to a string. TouchDesigner allows the programmer to insert operations between objects. By always ending a string in a Null it becomes very easy to make changes to the stream without having to worry about re-exporting parameters. Finally all of this ends in an Out. While the Out isn’t necessary for this string, at one point I wasn’t sure if I was going to pass this geometry into another component. Ending in the Out ensured that I would have that flexibility if I needed it.

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