Coon's Patch Examples
Hakan Tiftikci Turkey htiftik@yahoo.com
Introduction
Coon's patch defines a surface by 4 curve segments that are connected in end-to-end, forming a closed curve chain. For left, right, bottom, top boundary curves denoted by , convex sum (blending) defines two lofting surfaces from to and to .
First patch interpolates and second patch interpolates Adding two patches
and evaluating at boundaries yields
this shows that left boundary curve of , which is sought to be has extra term that can be modelled by Expanding yields
from symmetry, there is no need to perform same procedure for other direction (~ bottom,right). The final form of patch to interpolate all four curves is
Initialization
Definitions
3D Coon's Patch Example
Define control points for 4 boundary curves
Define 4 Bezier curves
plot corner curves
Plot control points for four corner curves
Define Coon's patch
Plot defined Coon's patch
2D Coons Patch example-1
Define control points
Define corner curves
plot 2D patch
plot corner curves and surface
2D Coons Patch example-2 : square net with equally rotationg tangents
animation for the sweep of tangent angle
2D Coon's Patch example-3 : grid generation for nozzle like geometry
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