Curved + Filleted Stair - Offsetting portions of poly line by different distances

Hi all,

I've designed a stair (first photo), loosely based on the stair in the photo below. I want to get a basic definition into Grasshopper so I can change change the angles and areas in the plan, tweak the tread depths, etc. without having to manually re-build the entire model every time I want to tweak it. I am a newish Grasshopper user though and haven't used it in a while. My first attempt used a simple offset to get the stair treads, but the problem is I want different sections of stair to offset different distances (one section at 280mm deep, one at 600mm deep etc). So in my second attempt I tried to use point, drew lines between them, determined the tangent at each line midpoint and shifted the points along that vector. After which my plan is to re-create a polyline and fillet with the same fillet radius. This is an extremely clunky way and I realize there must be a better way. I am surprised there doesn't seem to be anything similar online or in this forum though. If anyone has time, I would much appreciate some help as to how to better design this definition. Thanks!

Attachments:

5522.gh, 12 KB
5522.3dm, 55 KB
For GH Forum.pdf, 20 KB

Replies to This Discussion

Permalink Reply by Joseph Oster on November 7, 2017 at 3:17pm

Points that establish the initial polyline are internalized.

Attachments:

steps_2017Nov7a.gh, 22 KB

Permalink Reply by Seank on November 9, 2017 at 12:33pm

Thanks Joseph! I'm going to sped some time figuring out whats going on, but that is exactly what I was after. cheers

Permalink Reply by Joseph Oster on November 9, 2017 at 12:42pm

It has distinct limitations, as you'll soon see, caused by overlapping extended lines. Too many steps, for example, causes problems. It's complicated to do in a general way, especially if you want to add flourishes like those in your second image. Very terrain-dependent, probably easier in the end to do by hand. Not that this is the only way to code it, of course!

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