30485pb01 Windscreen 8 x 6 x 3 Curved Top Angled Canopy Pattern, how to finish?

Conditional lines - was Re: 30485pb01 ,,,
Conditional lines exist so that parts with curved surfaces, that would otherwise have no edge, can have an edge that shows only when the angle is right.

Think of a cylindercone made of 16 triangles with one point at the top, and the other two on a 16-agon at the bottom. At the side of each triangle you'd like an edge, but only if that edge will be at the side of the cylindercone. So how do you know if it's at the side?

Well... each edge is shared by two triangles. If the base of one of those triangles goes from left to right (eg. out the front), and the base of the other goes from right to left (eg. out the back) then the edge is at the side of the cylindercone. Otherwise it is not. SO we can use this to set up control points.

See the attached file. I've marked the cond-line so that it, and its control points are tan normally, but the conditional line shows up black when it's activated. Play around with rotating this and see what happens to the triangles and lines when the black line appears and disappears.

Hope that helps.

Attached Files
.dat   conddemo.dat (Size: 974 bytes / Downloads: 0)
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Conditional lines - was Re: 30485pb01 ,,, - by Tim Gould - 2012-03-24, 22:35

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