Non-photorealistic Rendering

NPR is the area of computer graphics that makes images
resembling traditional artistic works. In my research,
I have helped computers to create numerous images in a
variety of different artistic styles, some of which are
traditional media and some of which are unique.

Stained Glass Windows (download 5.8 MB)

Prior to this work, stained glass had not been much treated by non-photorealistic rendering practitioners. This work provided an automated method for transforming an arbitrary image into a stained-glass version of that image. I used segmentation to obtain an initial set of tiles, and morphological operators to get smoothed tiles. Then, tiles were colored by choosing from the palette of heraldic tinctures, and a displacement-mapped plane rendered to obtain a final image.

Wax Crayons (download 7.5 MB)

Here, we have a physically-inspired model of wax crayons, suitable for interactive stroke-based drawing. Paper is represented by a height-field texture, and a crayon is modeled with a 2D mask that evolves as it interacts with the paper. Wax deposition is computed based on the crayon contact profile, contact force, and friction. Previously deposited wax is smeared by crayon action, based on wax softness and contact information. The distributed wax is rendered using a simplified Kubelka-Monk model, which approximates light transmittance and scattering effects.

You might also want the original paper (download 2.9 MB)

Image-Guided Fracture (download 2.4 MB)

This work makes images of cracked surfaces from an input line drawings. The cracks are the boundaries of Voronoi regions in a weighted graph, where the distance between nodes is path cost in the graph. Modifying the edge costs gives control over the placement of region boundaries.

Felt-Based Rendering (download 3.5 MB)

Felt is mankind's oldest and simplest textile, composed of a pressed mass of fibers. Images can be formed directly in the fabric by arranging the fibers to represent the image before pressure is applied, a process called "felt painting". Here, we describe an automated synthesis method that transforms input images into felt-painted images.

Stipple Placement using Distance in a Weighted Graph (download 5.0 MB)

This stipple placement method provides extra emphasis to image features, especially edges. We use distance through a weighted graph, similar to Image-Based Fracture above. Stipples are placed on the frontier whenever the current distance exceeds a threshold; since the frontier is mostly expensive parts of the image, we get good stipple placement.

Stylized Black and White Images from Photographs (download 5.7 MB)

We create two black and white versions of an input image: a base layer, using graph cuts, and a detail layer, using a variant of local histogram equalization. We then combine the two into a single output image that contains detail where the input was detailed, and that is flat-colored where there was not much detail.