Animations: UV Emission Data

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In the scene, a shot of particles is emitted from a Plane object using ‘Polygon Area’ mode and in the emitter's Extended Data tab, the 'UV Emission Data' switch is turned on. The texture on the Plane, an animated noise, isn’t used to control emission of the particles, but instead it controls the particle radius. The radius changes so that it is zero on black areas and maximum size (set at 3 units here) in white areas. Grey areas will give the particles a size between these values. Since the noise is animated, we want the particle radius to change as the animation is played.

This technique uses data mapping. The particle radius is mapped to the brightness of the texture. Each frame, for each particle the texture is sampled at the UV coordinates stored in the particle. These coordinates won’t change but the colour at those coordinates might do so. Internally the brightness is calculated as a value from 0 to 1, and then this is multiplied with the maximum radius value, which is is 3. This gives us a radius from 0 to 3 which will vary as the texture varies on the object.

Page last updated September 24th 2021