How do I do a non-proportional resize of a fill?

[Anonymous]

Q: How do I select an irregular polygon fill, and then resize it's overall height without changing it's overall length?

Background:

I'm trying to make a height-control envelope along a boundary line. My local building regulations stipulate that the building should fit within a height envelope defined as 2.5m up from the contour at the boundary, and then a plane that is 45degrees in from the top of that.

I'm attempting to find the easiest way of modelling the envelope. I've done it using meshes and a fair bit of manual calculation; the Mesh to Roof addon; and SEOs.

However, using OBJECTIVE, or a Beam with a custom profile, to create the 45deg plane, would be easier:

1) In a section view, aligned with the boundary, trace the contour of the mesh along the boundary as a fill. Duplicate it and offset it a few mm. Subtract it from the original fill using the SPACE-select/magic wand method. Effectively ending up with a thin "line" (but actually is a closed polygon) that follows the boundary.
2) Make that a "section" profile, then extrude that into the property, with a 45degree tilt on the object.

Only problem is that the section is the profile looking along the tilted object, not the un-tilted object, so the moment it's tilted it no longer follows the correct shape of the boundary.

The workaround is to "squish" the section down, depending on the angle of tilt. For 45degress, its height needs multiplying by 0.707.

Now I can't do this once the section profile is created by adjusting the profile's height (neither with OBJECTIVE nor a custom-profile Beam), so I need to do it to the fill before I create the section.

How do I select an irregular polygon fill, and then resize it's overall height without affection it's overall length?

[Brett Brown]

Why aren't you using the Tools supplied by Cadimage that does this automatically? i.e. Site and Massing Tool

[Dwight]

You need to revisit the "Custom Profile as a BEAM" approach.

Your beam profile would include the height at the property line, the 45 degree incline and end at the maximum building height.

Draw the profile as a polyline beam where multiple segments are placed in sequence.

Elevate the endpoint of each segment in 3D to conform to the site contours. [see illustration for pet palette icon.]

The beam segments won't unify - use the SEO to trim off ugly overshoots.

If the solidity bothers you, make the complex profile stripes instead of one plane - they will read like dashes in section.

[Erwin Edel]

I would use a polyroof and then use the shape created by that to make a mesh out of it. You can see all the highest points in plan view (add polylines to mesh to create new points). And you can elevate the points to their proper z-value in 3d. This would be the fastest way in my opinion.

Polyroof settings:
basic elevation: 2500 mm
first part height: some rediculous big number like 50000 mm so all parts intersect
angle 45 degrees

magic wand your irregular shape and you have your roofs. Now magic wand a mesh on top of it, draw the polyline to help you find the highest points, etc.

Good luck

[Anonymous]

Thanks guys, for the speedy replies and suggestions.
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Brett: Good call - I hadn't looked at that addon, since it didn't come with the Educational download packs for Cadimage. I've since found it as a separate download from Archicadselect.com. I've looked at the manual, and the example they illustrate is a flat property. Do you know if the produced "Envelope" will follow the mesh, no matter how sloping the terrain?

Dwight: I hadn't thought of using beams facing along the property line, not inwards, so thanks for the suggestion, and illustration. It's not quite what I was aiming for, fully - places where the boundary line is straight and the contour of it heads uphill/downhill in a convex shape, the 45degree planes of the two consecutive beams don't meet to form a continuous surface. It will be a good quick technique though, for looking at discrete segments of encroachment at a particular points along the boundary.

Erwin: You may have misinterpreted - the property is actually a rectangular area, not an irregular shape, but the elevations along all boundaries are very irregular, so a polyroof won't be suitable.
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I've actually be experimenting with a number of techniques, and I think I've cracked it, both for speed, visual quality and usefulness. I'll post a tutorial (my first!) when I've refined the speed aspect.

So I've solved my larger problem, but the smaller question still remains (for other future circumstances)... Can I select an irregular polygon fill, and then resize it's overall height without affecting it's overall length? It seems such a simple operation (and common in all other vector apps), that I can't believe it's not possible.

[Brett Brown]

peter_h wrote:
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Brett: Good call - I hadn't looked at that addon, since it didn't come with the Educational download packs for Cadimage. I've since found it as a separate download from Archicadselect.com. I've looked at the manual, and the example they illustrate is a flat property. Do you know if the produced "Envelope" will follow the mesh, no matter how sloping the terrain?

Yes it does follow any shape mesh and follows the contours