Materials: luminous surfaces

In our ongoing series exploring materials and shaders, this issue we look at luminous surfaces

I f you’re new to CGI, you may feel that there are far too many tools to choose from in a dizzying array of software. This series aims to break everything in CGI down to the very basics, so that every artist can be armed with the knowledge of which tool is best. Let’s continue exploring materials and shaders by looking at luminous surfaces.

Lighting is one of the key skills to master in CG, and learning what each of the light types can do really helps artists mimic the real world in their CG scenes. The issue is, not all lights are… lights. A lot of objects emit light, a classic example being the rear of a firefly. So how do CG artists re-create emissive objects? They do it through the use of luminous effects within the material itself.

The luminance properties of a shader/material are some of the most fun elements of texture work, as they can bring a scene to life instantly, whether it’s lava from a volcano or the screen of an old TV set. As the luminance channel is usually interacting with a wide range of colours from the shader, it really adds pop to a scene.

Dependant on the render software being used, the luminance properties of a material can have a lot if not all of the same properties as a light object, making them truly powerful and a key part of a compositing workflow. Clever use of luminance properties can bring big improvements to a scene, especially for effects that would be quite difficult to create with light objects alone. Motion graphic UI elements for example are really enhanced by the use of emissive properties.

As luminance materials are embedded within a material, they can use the same sources as other parts of the material, for example animations for the screen of a TV can be played through a luminance channel, creating realistic interactive lighting.

In fact, luminous materials can also be used as actual lighting, for example when lighting a product shot. The full range of modelling tools from the application can be used to create easy-to-preview light shapes to enhance the reflections in a scene.