<J22>
the lower are polyhedron .. is there a way to get the result with a hull ? the upper are with cylinder and linear_extrude(slices=10) - both led to that edge between both. ( the internal hull seems to render faster then my polyhedron);
<J22>
1sec < 4sec
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<peepsalot>
a (convex) hull() can technically be used to create any convex shape
<Scopeuk>
J22 those bottom shapes to me look like two pairs at the bottom sphere, cylinder hull and at the top a pair of cones (cylinder with differing d1/d2 values)
<J22>
peepsalot well obviously not in scad as the hull ignores the slices
<peepsalot>
ignores what slices?
<J22>
scopeuk there are 4 objects at the bottom two polyhedra and above two hull() generated
<Scopeuk>
J22 yes I assumed we were only debating the construction of the lower two
<Scopeuk>
perhaps I misunderstood the query
<J22>
peepsalot the slices from the linear extruded circles (cones) - you get very irregular faces on the surface but between both are more or less only 2(4) faces
<J22>
scopeuk i want the second ( two cones) result with a hull () instead of a polyhedron
<peepsalot>
so just do a hull on two cones
<J22>
peepsalot did you see the picture? because exactly this is not working.
<peepsalot>
yes i see the picture, and i have no idea what is right or wrong about it without knowing your intended shape or what script produced it
<J22>
when using a hull i got that diagonal edge between both objects
<J22>
probably that piece is concave - in linear extrusions this is solved with peepsalots improved slices or segments - but a hull didn't use those
<peepsalot>
yep, well the sides transitioning between an expanding cone and contracting cone, are not convex then... so a convex hull cannot be used to create that shape
<Scopeuk>
I wonder if defining a central cuboid might fix it
<Scopeuk>
well "fix"
<Scopeuk>
short answer nope
<Scopeuk>
you could manually slice your shapes and hull them with some for loop and an intersection with a cuboid covering the "layer" note entirely sure that wont just create the same visual artifact with more steps however
<peepsalot>
J22: hull does not ignore anything though. its just that concave parts get "hulled over"
<peepsalot>
didn't have any truncated cones on hand so used some light bulbs as very rough cone models
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<Scopeuk>
peepsalot dedication right there
<peepsalot>
:)
<Scopeuk>
I had a hard time fully wrapping my head around it but in essence its quite simple a full hull is doing essentially shortest lines between all pairs of points (effectively) and in this case we want to ignore the existence of some of those (the diagonal pairs) in favour of doing it in a "layered" manner which is what I did in the paste bin. its
<Scopeuk>
plenty slow though and probably holds no advantage over the polygon (if you have it setup)
<J22>
peepsalot is that cheese or a pancake
<peepsalot>
theraband
<Scopeuk>
you see I went to pasta
<J22>
interesting - seems to be latex .. good to know for tinkering
<peepsalot>
you guys clearly don't watch enough Joerg Sprave videos
<J22>
i thought he was using tubes
<Scopeuk>
in my defence there is only a lasagne sheet sized bit visible :P, is that the slingshot guy?
<Scopeuk>
google suggests yes
<peepsalot>
yeah, he uses that same material for his slingshots
<J22>
scopeuk those multi chained objects are normally much worse compared to a polyhedron (and they have steps)
<Scopeuk>
I don't think its the best solution, but its teh closet approximation of your shape "with hull"
<Scopeuk>
s/its teh/it's the
<J22>
yes .. (you could make the hull around each 2 steps to get rid of the steps)
<J22>
thinking about - it is clear as the sides are twisted which is always hyperbolic
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<Scopeuk>
yeh it wasn't until I tried the stack method it all clicked into place for me
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