Painterly Rendering for Animation

1. Painterly Rendering for Animation • The author starts with the assumption that painterly rendering is necessary or desirable. Most of the Introduction is spent justifying this point of view. • The second assumption is that current techniques are inadequate.

2. This technique solves 2 major problems with current approaches • The “shower door” effect. • Lack of frame-to-frame coherence. Both of these effects result from the fact that brush strokes are not positioned based on constant locations in Model Space.

3. Past Research • Created still images using brush strokes generated from 2D source pictures. [Haerbli] This does not allow for usefull frame-to-frame coherence (must be totally random or “stuck” to view-plane).

4. Past Research continued • Particle Rendering, which has been used before [Reeves], rendering particles in Model Space as simple 2D elements in Screen Space. This has not been used before for creating painterly images.

5. Brush Attributes • Image – typically a monochrome bitmap. • Color – obtained from a smooth-shaded rendered image. • Orientation – determined by a 3D-to-2D projection of surface normals OR surface parameter. • Size – scalar values are maped to a range of predefined sizes. • Position – determined by particle’s position in Screen Space.

6. Future Directions • In many cases single brush strokes are a very effective way of abstractly rendering repetative elements i.e. tree leaves. • The brush stroke size could be made constant relative to the screen surface. • Particle placement could be improved. • The brush strokes could be lengthened and deformed to follow curves.

7. Conclusions • That two previous rendering methods have been successfully brought together to solve the two major problems of “shower door” effect and frame-to-frame coherence. • The painterly algorithem produces images with effects similar to those used by impressionist painters.