Precise Ink Drawing of 3D Models

Abstract

Drawings made with precise pen strokes accurately reveal the geometric forms that give subjects their characteristicshape. We present a system for non‐photorealistic rendering of precise drawing strokes over dense 3Dtriangle meshes with arbitrary topology. During an automatic pre‐process, we construct an extended version ofthe edge‐buffer data structure to allow the calculation of shape measures at each mesh edge, by adapting numericalmethods used in geomorphology. At runtime, feature edges related to shape measures are extracted andrendered as strokes with varying thickness and pen marking styles. Stroke thickness is automatically adjusted byconsidering surface curvature. Pen marking styles and visual effects of ink distribution are both controlled by theuser. We demonstrate precise drawing strokes over complex meshes revealing a variety of shape characteristics.

IRIS: Illustrative Rendering for Integral Surfaces

“…For non-photorealistic rendering, approaches have been presented to reproduce numerous artistic techniques, such as tone shading [12], pencil drawing [4], hatching [27], or ink drawing [31]. In the context of integral surfaces, however, artistic representation plays a secondary role to an accurate depiction the structure of the flow as captured by the surface.…”

Silhouette rendering based on stability measurement

“…The visual result achieved by the precise ink rendering style using our stability measures is comparable to that of the more time consuming measures used in [Sousa et al 2003]. This ink stroke method requires additional time compared to our local rendering method due to the calculation of vertex normals.…”

“…Another use we have found for our silhouette stability measures is to use these measures to create filled ink strokes as described by Sousa et al [2003]. In this paper a filled ink stroke is described as ribbon a, b, b , a where (a, b) are the vertices of a polygonal mesh and (a , b ) is found "by extruding its vertices (a, b) in the direction of their normals (n 1 , n 2 ) [Sousa et al 2003].…”

“…In this paper a filled ink stroke is described as ribbon a, b, b , a where (a, b) are the vertices of a polygonal mesh and (a , b ) is found "by extruding its vertices (a, b) in the direction of their normals (n 1 , n 2 ) [Sousa et al 2003]. The amount of extrusion in originally used in [Sousa et al 2003] is based upon the curvature of the mesh multiplied by a user defined amount. One can think of the area of the silhouette edges as the area of the mesh an artist might place a silhouette stroke in.…”

“…In our system we achieve this by rendering the mesh in the object's chosen fill color with the vertices of its polygons displaced a small fraction along the reverse of the vertex normal. This is the same approach as used by Sousa [2003]. An example of silhouettes with and without hidden line removal is shown in figure 14 …”