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# a "Real" 3D Polygon

## Question

A GC I work with on some projects jokes : "It sometimes takes you longer to model or draw something than it does for me to build it!"

He's only half joking, & he's close to accurate in some instances. In this case I'm calling for a cricket on a complex roof, & the roof has been tough enough to model but the cricket has been a real bear. I have used a roof face, to create the cricket but how much faster this would be if one could just draw this as a 3D object.

So my wish is for a 3D Object I can draw either on the fly or with the help of 3D Loci that would give me intersection points in 3D. (So I guess that's a 2nd wish.)

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I just learned what a roof cricket is 😀

I draw objects like this all the time using loci guides and NURBS. I would draw three NURBS curves (degree 1 creates straight sides), convert each to a NURBS surface and Stitch & Trim them together into a solid.

It would be great to have a solids object that you could drag corner points around but it wouldn't be very easy to control until VW adds a 3d dragger type interface for point movement.

Kevin

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Posted (edited)
10 hours ago, Kevin McAllister said:

I just learned what a roof cricket is 😀

I draw objects like this all the time using loci guides and NURBS. I would draw three NURBS curves (degree 1 creates straight sides), convert each to a NURBS surface and Stitch & Trim them together into a solid.

It would be great to have a solids object that you could drag corner points around but it wouldn't be very easy to control until VW adds a 3d dragger type interface for point movement.

Kevin

Is the subdivision tool then perhaps a bit of an overkill?  I do think though that a simplified version may be helpful.  I haven't used the subdivision tool myself simply because it starts from an organic point of view.

Edited by Markvl

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@Kevin McAllister @Markvl - Regarding the roof cricket, I'm old enough, that my drafting classes included a lesson on Ballon Framing!

As for how I do this now is I make a Roof Face that mimics the size, angle & location of the cricket. The main Roof Faces will "hide" the Roof face / Cricket, so I then use a 3D Poly to get the shape of the Cricket then in plan I convert this 3D Poly to a 2D Poly & use this to edit the shape of the roof face.

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I don't understand what the problem is here... why is it so difficult to draw?

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Posted (edited)

@line-weight When I need a roof cricket, I have 3 or more Roof Faces that intersect. Even if they all have the same pitch, I have to find a wall to "fill in" the offending space so that it will drain properly & won't be a nice place for snow to build up. The cricket itself will be by nature at a different pitch.

Rather than a Roof Face I could use a series of extruded objects & Subtract Surfaces, but that means duplicating a bunch of roof objects.

Here's a grab of my playing with the roof in Annotation to get an idea of where & how big the cricket should be. If instead I had a "Real 3D" Polygon tool, I could use to fashion this shape & extrude it is my wish.

Subdivision may be good for some users but in my work it isn't a tool that I use as it's not very intuitive, & far too complex to use. That, & I'm not a fan of Blob-a-tecture. 😉

Edited by Jim Smith

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Oh, ok, is it to do with trying to draw it with the roof face tool and the limitations of that?

I never use that, when I draw roofs I model them directly as solids, I guess for the sorts of reasons you describe.

Roofs often being one of the most complex parts of a building envelope, they always seem to me to be  the least suited to being drawn with an inflexible tool.

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Yup, I get the rational for not using the roof PIO. I think I may have built one project & used it without having to break the roof into smaller parts. This project would have been the 2nd, until for zoning reasons we had to remove the gap between the two Noth / South parts of the roof

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A side note on the subdivision tool: It can be used in a "linear" mode, and is actually rather powerful.

For roofs, here is a "sample" method: Draw a 2d polyline describing the roof edges from above, push/pull that to some starting thickness, eg. 200mm for the eaves, the convert to -> subdivision, and set "iterations" to 0.

Of course the subdivision tool doesn't have the roof tool functionality as to components etc., but for some situations and especially massing it's practical.

Below is a screenshot of a subdivision roof made as described above.

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Where do you set 'iterations' to 0? I can't see anything in the subdivision OIP.

A reason I've not really used the subdivision tool is that it seems to create 'hollow' objects rather than solids, which means they don't section properly. You can convert to generic solid, but then you lose the edit capability.

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4 hours ago, line-weight said:

A reason I've not really used the subdivision tool is that it seems to create 'hollow' objects rather than solids, which means they don't section properly. You can convert to generic solid, but then you lose the edit capability.

The subdivision tool creating hollow object in section is an issue. Hopefully this will be corrected in a future version. I miss Jim W right about now.... @Matt Panzer is there someone who can speak to this?

Kevin

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54 minutes ago, Kevin McAllister said:
5 hours ago, line-weight said:

A reason I've not really used the subdivision tool is that it seems to create 'hollow' objects rather than solids, which means they don't section properly. You can convert to generic solid, but then you lose the edit capability.

The subdivision tool creating hollow object in section is an issue. Hopefully this will be corrected in a future version. I miss Jim W right about now.... @Matt Panzer is there someone who can speak to this?

The geometry a subdivision produces is a mesh. This would cause it to show as hollow with the clip cube (as all meshes do), but it should show solid in section viewports (as long as it's a closed surface). You may ask why we don't convert the geometry to a solid within the object. The answer is simply due to performance issues.

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@JMR Very innovative looking roof!

I guess I still would like the ability to just grab points in 3D and make an extruded object not a mesh, but a solid. This way in my example one could model the ply as well as the sticks that make up the assembly, & not have to fudge it in annotations. Guess I'm lazy & just want to do stuff easy & once.

In the pencil & paper days I would have just drawn this in section, then taken my measurements & transferred these to a plan view; the end.

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On 5/3/2019 at 12:41 PM, line-weight said:

Where do you set 'iterations' to 0? I can't see anything in the subdivision OIP.

When you eg. convert an extrude to subdivison:

And if you have already done it, in the OIP

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I don't get that option... I am on 2018; is it a 2019 thing?

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Well, bummer, it seems to be indeed. You can get similar results though by creating a subdivision primitive as cube in 2018 and continue from there. Not quite the same though.

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