Trouble with building a shape.

 From:  Michael Gibson
685.3 In reply to 685.1 
Hi Johnny, here are some more detailed steps.

Often times the first step is to try and identify some key structural curves that you can draw to begin working with. Sometimes you may construct surfaces from those key curves, or in this case you want to use them as a cutting object to slice up a sphere.

In this case to construct your curve, I can kind of see a pattern with an outside circle and an inside circle and some spokes. So that's what I drew to start with - 2 circles centered on the origin (origin snap comes in handy for many things like this) and then 2 lines between them which will form one spoke. After you draw one line, use Transform/Mirror (using origin snap again) to create the other one. You may need to come back to this step and tweak the placement of the lines to adjust the width of your spoke.

Do this in the front view, and click on the "Front" tab in the bottom bar to make the front view full screen.

So that looks like this:



Then the spokes are in a repeating pattern. A repeating pattern usually means you will use Transform / Array to construct it. In this case select the 2 lines, then use Transform / Array / Circular, pick the origin snap as the center point, and type in "6" in the Item count. Since Item count is the first option, you can just go ahead and type in 6 and push enter immediately, you don't even have to click in there first. Then push Done. You will often times push "Done" (or a shortcut is to right-click inside of a viewport) to signal that you're done with adjusting options and to accept the result.

So now with the array it looks like this:



Now the circles need to be trimmed into smaller pieces. To do this, select both circles and then run Edit/Trim. The prompt in the upper-right corner will say "Select cutting objects". That prompt in that upper right corner generally tells you what thing MoI is expecting you to do next. So in this case now select the lines. You also might want to un-check "Extend lines", because with line extensions turned on it will make extra cut up pieces that you don't want. I'm planning on turning this off by default soon, but right now it is on by default. So anyway, after you pick the lines and push Done, you are now at the point in Trim where you select pieces to remove or keep (or you can push done at this point to keep all sliced up pieces).

Select these fragments to remove: (note - if you make an error in selection like click on the wrong thing, hit undo or ctrl+z before clicking anything else and it will undo your selection mistake).



Then after you push done, you've got the curve finished up - select all the pieces and use Edit/Join to make it into one curve object:



Now use Draw solid / Sphere to draw a sphere in the top view centered at the origin. The size of the sphere is another factor you can mess around with to get different results.

After you have the sphere, select it and run Edit / Trim again, and select your curve as the cutting object. Throw away the middle and the back pieces, and then you will be left with this:



Select your sphere fragment, and use Construct / Offset / Shell to thicken it into a solid, I used a thickness of 1 unit here. Then I used Construct / Fillet and applied a 0.2 radius fillet to round the edges. The final result (viewed here during OBJ export with Display:shaded option):




I think my spokes are a little too long compared to what you wanted, probably the initial circles that I drew should have been a little closer to each other.

This is a good project example for NURBS modeling. This is exactly the kind of structured object that can be created very well and quickly using NURBS.

Again really the key thing is to identify curves to create to begin the process.

Hope this helps!

- Michael