Using Google Sketchup for dome modeling

[OpenD]

Aloha,

Anybody else using Google Sketchup to design the dome home of your dreams?

I'm using the free version and it's fabulous for visual thinking about home plans, because you can easily move pieces around on the screen, trying different different things until you find an arrangement you like, then helicoptering around looking at it from different angles and distances. There's even a sun/shadow modeling tool that allows you to plug in the latitude and longitude of your specific lot (or the nearest city if you are lazy) and then pan through the months of the year and hours of the day to see where the sun hits and the shadows fall. That saved me a big oopsie about where I first thought the vegetable gardens would go. And the free library of standard plumbing fixtures, kitchen appliances, doors and windows, and furniture means you can pull in realistic pieces of the puzzle to get a better idea how everything will look together.

The one thing I'm having trouble with is getting a good model of the shape of a Monolithic airform. Hemispherical domes are easy to make in Sketchup, as are supporting stem walls. But the Ecoshell airform I want to use is not hemispherical in shape, and I'm having trouble approximating its shape accurately using polygons or joined curves. It's not off by enough to be an issue in planning, it just bugs me that I can't get the shape right so that it looks like the real thing. (For non users, creating a dome model involves drawing a cross section in 2D using basic shapes like rectangles, lines, circles, and polygons, then spinning the 2D shape 360 degrees to generate the 3D shape)

Any suggestions?

Mahalo,
OpenD

[wingman]

I have tried several tools for modeling domes over the years including Autocad(Intellicad), Blender and finally Sketchup.
Sketchup seems to be a superior tool for all the reasons that you list and more.
To draw a non hemispherical dome just draw the profile on one plane and then revolve it 360 degrees using the FollowMe tool.
If you wanted to draw a partial dome just revolve it less than 360.
By the way the shape that you revolve around does not have to be round either.
Attached is an example of a 40' dome profile that I created before rotation.
It took several tries drawing the curve using several arcs joined together and then lots of tweaking to get the shape that I was looking for.
Sketchup is a great tool with almost unlimited potential but it does take some time to learn it.

Jim

[3dO]

When I draw a dome using Sketchup I start by drawing a circle for the floor diameter. Then draw a line across the diameter. Next draw a vertical line the length of the radius. Then draw a half circle. Erase one side of half circle. This will leave a quarter circle. Select this quarter circle and use the scale tool to change the size of the verticle axis. This will allow the profile to be made oblate or prolate. Then use the followme tool to create the dome. It sounds a lot more complicated than it really is.

[wingman]

That is one of the interesting aspects of Sketchup, that there are many ways to achieve the same results.
I had not considered the scale tool for this purpose but it makes perfect sense.
Thanks John for the alternate method.
I'll keep this in mind for any futher dome drawings.

Jim

[OpenD]

When I draw a dome using Sketchup I start by drawing a circle for the floor diameter. Then draw a line across the diameter. Next draw a vertical line the length of the radius. Then draw a half circle. Erase one side of half circle. This will leave a quarter circle. Select this quarter circle and use the scale tool to change the size of the verticle axis. This will allow the profile to be made oblate or prolate. Then use the followme tool to create the dome. It sounds a lot more complicated than it really is.

Yo 3dO, thanks, that's exactly what I was looking for. I already knew how to create the hollow dome shape, but I couldn't get that oblate curve quite right using arcs and polygons and such. They were close enough for general planning purposes and visual thinking, but they just never quite looked right, and the tool doesn't have the complex curve technolgy I have in other drawing tools. Never though of "squashing" a hemisphere with the Scale tool. Now I can just pop that oblate curve on top of the 3'6" stemwall, use the Offset tool set for the wall thickness to create the same curve inside, delete the middle, spin it with Follow Me and voila! A very good hollow dome shape that I can "walk around" inside and out using Sketchup. That's very, very helpful. Fabulous.

For one thing, I think I'm going to be looking for a shorter refrigerator.

And for another, I can stop having to explain to people when i show them my sketches that "that isn't quite right, it's more like the shape of a raw egg yolk on a plate."

Mahalo,
OpenD

[OpenD]

Yo 3dO, thanks, that's exactly what I was looking for.

Whoo hoo, I just got the other half of the solution I was looking for... by creating that curve inside a rectangle, then deleting the inside shape, I wound up with a negative space template I can try against various components to see how far out from the wall they need to go... or how much they need to be trimmed at the top in back to be able to fit the curve better. This is VERY useful.

BTW, to share a tip I use a lot, since Sketchup uses polygons instead of true curves, I've found a good compromise on the number of faces to use in a "circle" is 36, because then the dome is in 10 degree segments. You can use more facets to get a smoother curve, but then the object sizes get very large and file loading starts taking a lot longer, changes in perspective are slower, etc.

Mahalo,
OpenD

[OpenD]

In case anyone isn't following my comments about making a try guage for the dome shape I'm planning on using, here's what I mean. This tells me that this particular JennAir refrigerator (model from the Sketchup library) will need to come out from the wall about a foot to clear the curve. It's not accurate enough for cabinet work, but it is way better for rough planning than the Guestimate method.

That's the stock Sketchup guide alongside, who just happens to be the same heigth as me, so that's handy, except I really ought to add some weight to him, and a grey beard, to have a better likeness.

Another value of having a more accurate template of the shape is that it helps me to visualize and estimate some intersecting elements, like the straight walls that will be used to enclose a courtyard space. Again, it's not close enough for actual use on the ground, but great for visualization and planning and estimation. Material will be cut using the "Measure Twice, Cut Once," technique.

Mahalo,
OpenD