3D modelling tips: creating a blur effect

Digital artist Hugues Giboire explains the process of modelling a bokeh effect.

In one of my recent personal works (above), I wanted to use the negative space of the blue velvet background of the scene
to create an effect reminiscent of the stars against the night sky.

In general, I tend not to leave anything to the post-processing stage. I take pride in making sure that everything I want the viewer to see is physically present in the scene. This is one luxury that using an unbiased renderer offers: if I don't want to fake it, then I don't have to. I can simply model it. In this specific case, I decided to fill the volume of the scene with dust.

Dust specks floating in the scene create a bokeh effect against the background

Starting from a cylinder that I then deformed and sculpted, I created a dust speck with convoluted shapes offering more surface area for the light to hit. It is modelled to scale, which is less than a millimetre in diameter.

The material created for the speck has soap-bubble characteristics: firstly it is very specular to reflect as much light as possible; and secondly it is finished with a thin film in order to create mild colour variations, dependent on the viewing angle of the surface.

In Maya, I used a simple emitter and filled the scene with particles that were then used as input co-ordinates to generate the thousands of instances it takes to create a convincing effect in the final render. Once out of focus, the specks that catch the light will bloom into a fairly convincing bokeh effect.

Words: Hugues Giboire

A 3D artist with more than 20 years' experience in the CG industry,
Hugues Giboire is a BAFTA nominee for artistic achievement in video games. This article originally appeared in 3D World issue 180.