1MAE 455 Computer-Aided Design and DraftingThis image cannot currently be displayed.Freeform Surface ModelingImage from Chad DickmanImage from Brent LiedkeThis image cannot currently be displayed.Image from Jeff LeismerImage from Michael BieryImage from Christopher RockMAE 455 Computer-Aided Design and Drafting2Review of Sweep Operations• Types of sweep operations are:–––• Elements of sweep operations are:––2MAE 455 Computer-Aided Design and Drafting3Types of Freeform Surfaces1. Surfaces from points• Point interpolation• Control points• Point cloudSurface is incident with a grid of points.Grid of points “pull” surface.(Not necessarily incident.)Best fit to jumble of points.(E.g., laser scanned data)MAE 455 Computer-Aided Design and Drafting4Types of Freeform Surfaces2. Surfaces from multiple sections• Ruled surface• Through curves (loft)Matching points on each curve are joined by straight lines.Best fit of surface to curves. (If only two curves, same as ruled.)3MAE 455 Computer-Aided Design and Drafting5Types of Freeform Surfaces2. Surfaces from multiple sections• Through curve mesh• Advanced/variational sweepBest fit to two sets of curves, one set for each direction.Similar to basic sweep, but “guide rails” can be used to change size and orientation of cross-section.Sketch constraints may also be used for control of swept profile.MAE 455 Computer-Aided Design and Drafting6Types of Freeform Surfaces2. Surfaces from multiple sections• Bounded plane or surfaceBest fit to bounding curves.• Can sometimes also control edge tangency/curvature to match adjacent face.4MAE 455 Computer-Aided Design and Drafting7Types of Freeform Surfaces3. Surface construction from existing surfaces• Offset surface• MidsurfaceOffset surface is same perpendicular dist-ance from original surface at every point.Can also offset in specific directions.Midsurface is same perpendicular distance from both original surfaces at each point.• Both of these surfaces are associative.MAE 455 Computer-Aided Design and Drafting8Types of Freeform Surfaces3. Surface construction from existing surfacesOthers we already use:•••5MAE 455 Computer-Aided Design and Drafting9Types of Freeform Surfaces4. Operations on sheets and faces• Trim sheet• Split face• Sew faceMAE 455 Computer-Aided Design and Drafting10Practical Hints• Choosing loft direction: • Fixing twist:• Difference between sweep and loft:• Rounding