Intersect function

DELFTship forum Hull modeling Intersect function

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    • #39524

      I’ve drawn a kajak. It has the layers bottom, side, deck, coaming, and paddler. All is well so far.
      Now I’d like to cut out the hole in the deck inside of the coaming, and the unused parts of the walls of the coaming as well.

      So I extruded “wall” of the coaming vertically to cut through the deck.

      Then I run the function “Intersect”.
      I’m able to get the new control points in the coaming only, but not in the deck.

      This means:
      -selection of “coaming” and “deck” works -> creates new control points in the coaming, but none in the deck
      the function does what it says: new control points in the coaming, as selected in the function
      the unused coaming parts below the deck can be removed

      -selection “deck” and “coaming” does not work -> no new control points in the deck, nor in the coaming
      removing not used parts of the coaming (below the deck), and the deck inside of the coaming cannot be made

      Seems that I’ve something misunderstood. Any help is highly appreciated.

    • #39525

      Hi Ruedi!

      When I use the INTERSECTION function, I noticed that the layers’ selecting order is important. “Deck” then ” Coaming” won’t give exactly the same result than “Coaming” then “Deck”.
      So, I’m used to always use both selections, one after other, to get as many intersection points as possible, then I connect the most convenient points to get the right intersection curve, the I delete the surplus surface.

      An other way to do can be to use the OFFSET SURFACE function to draw a temporary surface parallele to the deck, above it, to draw a vertical cylinder thru both surfaces and to ovalize it (the *temporary* coaming’s *template*). Then you use the INTERSECTION function to draw the coaming edges and connect them drawing one afet other each polygon of the coaming.
      Finaly, you have to punch the hole and delete the temporary surfaces (offset deck and coaming template).

      Using this “temporary surface as template” method can be interesting when you have to draw many times the same thing on many places (portholes for example). Instead of deleting the template, just move it to the new place, ask the new Intersection points, draw the new wafer side, delete new unused surface, move, draw, delete again… and again…

      Is it clear? Does it help?

    • #39530

      Hi Icare
      I know how the intersect (not intersection) function works, and the importance of the layer selection order as well. I’ve tried both orders, and the combination of both orders as well before asking here. None of them delivered what I want to get.

      I’ll try your suggestion to use an offset surface. My understanding
      -I draw a parallel deck surface above the existing deck (tool / Offset surface)
      Which value for offset?
      Which Layer?

      -I draw a vertical cylinder through both deck surfaces
      Which diameter and height?
      Ovalize to what? My coaming is not oval.
      Which Layer?

      -I run intersect
      Which layers? Which layer sequence?
      One or more times with different layers?

      -What do you mean with “draw the coaming edges and connect them drawing one afet other each polygon of the coaming”?
      I’m puzzled

      -If and after all intersection control points are o.k., the deletion of all unneeded surfaces is clear to me

      have you checked to run intersect with my drawing?
      It really does not delver the intersection points needed for proper surface deletion of the deck surfaces inside of the coaming (my opinion)

      kind regards

    • #43652
      Anneler Ruedi

      found out how this works now.

      I did al right, BUT I’ve overlooked the info in the delftship manual, that the surface in the layer (layer one) that should be cut by layer two (the cutter) must have a rather fine net of edges. The layer to be used for the cut seems not to be critical, but the layer that should contain the new control points is.

      New control points are only generated in existing edges that are defined on layer one – the cutted one – and are cutted by layer two – the cutter.

      There are no new points created in a surface!

      Stupid, huh? But this has eaten a lot of my time for trying to make something happen that really does not work – because of way too less edges in the surface to be cut.

      They can easily created by selecting the edges around the area where the cut lies and then clicking “split advanced” one or more times before the intersect attempt.

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