# Outline Rendering of 3D Models (POV-Ray)

Xah Lee, 2010-11-09

Here are some images:

Outline rendering of 3D models. Source

The interesting thing about these is that they are computer rendered 3D models (in POV-Ray), not created in 2D drawing programs such as photoshop or Inkscape. Am surprised to learn, that this is not possible with POV-Ray (See: Introduction to POV-Ray) Instead, you have to use a special add-on software.

The outline rendering is significant, because it has a lot applications, especially in illustration or technical drawing. The essence is that this illustration-style shows the important aspects and hides away irrelevant details, such as complex meshes in wireframe rendering or the realism detail from ray-tracing. (much like black'n'white photos make you see the composition) My need for 3D modeling is mostly illustration of geometry, so i really want to render 3D objects like this. (See: Illustrating Geometry with POV-Ray, • Requirements For A Visualization Software System For 2020)

Here's a example of illustration of so-called “stereographic projection”.

A illustration done in Mathematica. (See: Stereographic Projection.)

It is rendered in a wireframe mode. Note, a desired rendering, is to actually hide the meshes behind the sphere.

It's somewhat surprising that POV-Ray can't do it, thinking about all the trouble it went thru with ray-tracing. If you think about it, it does make sense, because the essence of illustration-style drawing is a parallel projection from the camera, but realistic 3D rendering is about tracing every light ray to render every point on the object. However, i think the 2 issues are still quite related and is not something totally separate. I think the fact POV-Ray cannot do it is just a particular historical or idiosyncratic reason. Because, for example, when rendering in POV-Ray or any 3D modeler, you have to have algorithms that hide invisible parts. (that is, you shouldn't see what's behind a box) The hiding invisible object algorithm is part of the parallel projection from the camera, same with rendering in outline mode.

A screenshot of a character in Second Life (outline renedering in real time).

Note that Second Life (a virtual world 3D “game” application), is capable of outline rendering, in real time. See: Toons in Second Life.

(thanks to namejuseijin for mentioning the POV-Ray outline-rendering add-on.)

2010-11-10

Thanks to meowcat for mentioning Penguin3D at. It's a plug-in for Rhinoceros 3D and AutoCAD. It does outline rendering. Penguin3D has a gallery at penguin3d.com. Here's a example:

A mall, rendered in outline. Animation courtesy of Heath Satow. Source