An approach to visualizing transparency in computer-generated line drawings

Expressive Rendering

“…A transparent surface is "textured" with uniformly distributed opaque short strokes, locally oriented in the direction of greatest normal curvature and of length proportional to the magnitude of the surface curvature in the stroke direction. Copyright of IEEE, used with permission Hamel et al summarized principles of depicting transparency in handmade line drawings, and developed a method to generate similar, but computer-generated line drawings [Hamel et al, 1998]. (see Fig.…”

“…Three different ways of expressing transparency in a line-drawing [Hamel et al, 1998]. (a) Increasing the thickness of lines; (b) Inserting additional lines; (c) Using a different style (stippling).…”

“…[Hamel et al, 1998]. Lines are intersected with the edge of the mask and the part inside is drawn with a thickness based on the brightness of the transparent picture.…”

Transparency in Interactive Technical Illustrations

“…Hamel et al 13 recommend to use an image-space method by establishing an object ID buffer and an edge extraction filter. However, this method is very time-consuming as you first have to render the objects with an ID tag, find the edges, vectorize these edges to 2D lines, and-with the help of these linescalculate the distance of each pixel to the outline.…”

Transparency in Interactive Technical Illustrations

“…Neither has transparency yet been addressed in automatic technical illustrations, nor has it been addressed extensively in other fields of non‐photorealistic rendering (NPR). To the authors' knowledge, the paper by Hamel et al 13 is the only work specifically dealing with transparency in NPR. They concentrate on transparency in line drawings, whereas this paper is focused on illustrations consisting of smoothly shaded, colored surfaces.…”