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In this video, we'll explore two critical editing tools: the Trim and the Split. First, the definitions. Both commands are looking for where geometry is intersecting. A Split will break it apart leaving all of the pieces remaining. A Trim will create a break and then delete the leftover parts. And like many other editing commands in Rhino, both commands work the same way, whether you're working on curves or surfaces, or even a mixture of both. Let's start off by doing a Split first. I'm going to go to the right view and maximize it, and we've got some construction geometry for this robot arm.
First, I'm going to split the circle to the two rectangles. So, here is the Split command on the main menu. It says, "Select objects to split." I'm going to select the circle. Hit Enter when I'm done and then select the two cutting objects, and hit Enter or right-click when done. So, now we've split them apart with all the pieces remaining. We can continue and do another split, this time splitting the two rectangles.
So, we select both and then hit right- click, and then you have to pick the pieces that have intersections, so that's multiple pieces now. So, at this stage, we have leftovers that are no longer needed, and you can select and delete. So, there is the robot profile with one way to do it for his arm. Let's try a little bit quicker method called Trim. Here is the Trim icon on the toolbar. We're going to select the circle to cut, Enter when you are finished selecting, and then pick the pieces to be removed.
But repeat that now going backwards. Selecting the two rectangles as cutters, right-click to accept, and then the parts to be removed. You might notice that there is a lot of extra clicking. So, Rhino is set up so you can Trim or Split two or three or more entities to another two or three or more. So, that's why they always ask you for the right-click to accept. So, it doesn't make a lot of sense when you're splitting or trimming one curve to another single curve. It makes more sense when you have larger groups, so keep that in mind.
Now I'll show you a great little shortcut for doing a lot of these steps faster. It's kind of a buried command. It's called Curve > Curve Edit Tools > Curve Boolean. So, this is asking you for an input group of curves. You can just draw a box around them. Enter when done selecting or right-click. Now, we're just going to define some regions, but before I do that, I want to say Delete the Input, All. I only want the end result. So, we start clicking inside these regions and you'll notice how they highlight or shade.
When you're done with the regions you want to keep, you can always subtract some. I'm going to right-click now, and it found all the intersections and removed all the extra pieces in one command. Let's talk about same commands with curves and surfaces. I'm going to switch back to All Viewports, and maximize Perspective. So, here I have got a backup head copy with some surfaces joined and then a curve that happens to be sitting on the surface.
Let's see how this works. We're going to use the Split command. Objects to be split. I'm going to click on the solid, right- click to accept, cutting objects will be the curve, right-click to accept. Now you'll see where this surface has been spliced out. Even though the curve was on top of the surface and not really technically intersecting it. So, this is a great command for little details, where you might want to move this face back.
I'll just click the Nudge key a couple of times, and you can build a surface on the edge. Let's try a projection type command. Now if you have a simple enough surface here and a simple enough curve, they don't even have to intersect. It will actually calculate the intersections by projecting through the construction plane, which is down below. Let's try to split it, objects to split is the head, right-click to accept. We can pick one of the circles, right- click to accept, and so it has done a nice projection vertically, and split that right out.
I'm going to go ahead and undo. If you have more complicated geometry, then it's just one additional step. Let's take this Surface command, extrude one of those circles straight. Right-click to accept. So, this is an extra step, but it's a guaranteed way to find the intersection. So, we'll go ahead and split that head, select, right-click to accept.
Cutting objects is a cylinder, right-click to accept, or I can just throw that away now. So, we've made that cut. Use of splitting or trimming or even curved Booleans depends as much on your specific project as it does on your personal preferences. One good tip to try. As your model gets more and more complex, you might want to begin using the Split command over the Trim command. On more complicated models, Rhino sometimes cannot find the intersection, so by using Split, you're giving yourself the opportunity to use the different two sides to find the intersection.
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