Grasshopper

generative modeling for Rhino

# Drawing flat Rectangle Surface from Angled surface's highest edge

Hello.

I am trying to achieve something similar to bounding box for surface which is angled in both x and y directions. In short words -  I am trying to draw flat surface on top of angled surface with  base (first) curve on angled surface's highest edge. So afterwards I could offset surface on -z direction and build a beam.

Does anybody have any idea how to achieve that?

Here are some images from pyramids I am trying to make beams for + some sketch views from back view, so it would be easier to understand, what I am trying to achieve.

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Here's a definition that gives the rafter you want.  I'm not very adept at resolving path issues so it will only display one rafter at a time depending on what values you use in the the list item component (0,1;2,3 or 4,5).

Chris

Attachments:

Hello, Chris.

Unfortunately, there are some major issues, which it doesn't suit:

1. In your approach surface before extruding is being drawn from the mid curve/line, which is being offset to both sides and these side curves are making the upper surface. In this case it's not working, because I wouldn't be possible to produce/ cut such a beam (reason why mentioned in second point). I need to make surface from highest curve/line, like in drawings before.

2. In your approach surface is being extruded on Z axis, which also gives me different beam thickness than I would need.

Imagine, I have wooden beams and I wand to make frame for pyramid from them. To do less wood cutting I would just align beam in needed angle so the bottom surface would be parallel to ground. So, because of wood is being aligned - wood thickness is equal the distance between upper surface and surface offseted normal to upper surface. If I am extruding upper surface on z direction -  I am getting beams cross cut height not the beams thickness, because beams is aligned.

From this point it is clear that I have to do surface offset from highest curve/line not the mid line, because after cutting top surface on angle, there just wont be enough "wood" for part of beams  up from top/ base surface's middle curve/line (see image attached)

Do you have any other idea? Maybe you know how it would be possible to align bounding box to each of these surfaces (It would be the most easy way to do that)?

Trythis.

Attachments:

Rafter_Problem

The link above is for a screencast.

Chris

Chris, thanks!

This is what I was looking for.

Only one more thing:

Do you have any idea, how I could pick a "highest" curve projected onto roof surface and a highest curve's centroid surface not by typing integer on "item" component, but by picking the one which higher from ground? This is important, because I have pyramids with different low-high direction, so the same integer won't work for all.

This should sort out the proper lines and faces but you'll have to test it on your geometry to be sure.

Chris

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Chris, thanks!

I'm cleaning up my function at the moment. Will try it out asap and let you know, how it worked.

Chris,

Your approach is almost working for me. Only problem - I can't find a right highest point, because from ground plane extruded pieces, from which afterwards beams are being cut off, is being extruded different directions and because of that for some highest point is on start points but for some on end points.

I am trying to sort edge curves, but this far without any luck.

Do you have any idea how it could be made?

Otto,

You might want to try inserting the Flip component into your definition to get all of the curves going in the same direction.

We're about to get hit with a hurricane here so this may be my last post for a few days depending on power outages.

Chris

Chris,

I already tried that. Didn't work out. Curves remained same direction like before.

Take care! Hope to hear from you any time soon.

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