Frame-Coherent Stippling

Stippling is an artistic rendering technique where shading and texture is given by placing points or stipples on the canvas until the desired darkness is achieved. Computer-generated stippling has focused on producing high quality 2D renditions for print media, while stippling of 3D models in animation has received little attention. In this paper we present a technique to produce frame-coherent animations of 3D models using stippling as a rendering style. The problem for which we provide a solution is how to obtain an even distribution of stipples and at the same time ensure frame-to-frame coherence while shading changes over time. In our approach, particles are placed on the surface of the 3D model and adaptively rendered as stipples using OpenGL point primitives and the input model as a canvas. At each frame, the density of particles can be increased if necessary. Selection of particles during rendering takes into account the screen space projection of the edges of a polygon fan that surrounds the particles and the desired tone at the position of the particles. The rendering technique presented here can be applied to arbitrary polygonal meshes and can be extended to include grey scale textures, bump mapping and custom illumination models.