Creating a Wireframe using Contour Rendering

Minor Project Technical Paper Daniel Rolph

Contour rendering is a way of creating wireframe images without using the Toon render options, and without having to harden edges. It can also be used to create an outline around an object, give the impression of a drawing, or many other tricks.

The first step is to enable contour rendering. This is done by opening the attribute editor for the shading group that the material on the object in question. If you are making a wireframe, it is best to apply a Lambert shader with Matte Opacity set to Black Hole.

Expand the “Mental Ray” options in the group attributes, and click the box marked “Enable Contour Rendering.

Make sure that it is set to “Absolute Width”

The “Width” slider controls the width of the lines; it is the only way to control this.

Next, open the Render Settings, and set the scene to render using Mental Ray.

Open the “Features” Tab, and scroll down to the bottom.

Expand the Contours Tab, and click on the “Enable Contour Rendering” box.

Next, set Over-Sample to 3 (this improves the smoothness of the wireframe, by rendering it 3 times and averaging)

Then, set the Filter Type to “Gaussian Filter”

At the moment, rendering produces no lines, as none of the render options are enabled

Selecting “Around Silhouette (Coverage)” results in a line being drawn around the outside edge of the object.

Selecting “Around all poly faces” draws a line around every poly face. Usually, this will be enough to create a wireframe, but sometimes a few edges will be missing

Selecting “Around coplanar faces” draws a line at every hard edge that isn’t flat

Selecting “Front vs. back face contours” draws a line wherever a piece of geometry is in front of a different piece of geometry

To make a wireframe, enable:

• Around silhouette (Coverage)

• Around all poly faces

• Front vs. back face contours

It’s also possible to show the triangles that make up the polygons of the model without changing the geometry. To do this, enable:

• Around silhouette (Coverage)

• Around coplanar faces

• Between different instances

• Around render tesselation

• Front vs. back face contours

One final piece of advice: Since contour rendering is part of mental ray, it will take account of any smoothing you have done in the viewport. Therefore, it is usually a good idea to unsmooth the geometry of whatever you are wireframing, unless you want an extremely high-resolution wireframe.