Ray-traced diffusion points

Diffusion curves [Orzan et al. 2008] (DCs) has risen as an attractive vector primitive for representing complex colour gradients. Its flexible mathematical definition, taking curves with colour values as input, can be easily adopted by artists and designers because curves represent an intuitive approach to 2D drawing and design. However, the (Laplacian) diffusion process is computationally expensive and naive DCs (solving the large sparse PDE naively) are consequently unattractive as a practical vector graphics primitive. Lots of work has therefore been undertaken to identify a practical framework for defining and rendering DCs.