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Controlling extrusions from sketches / building a 3D solid solely through sketches
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So, let's say I've created the following solid by extruding different sketch surfaces to different depths.
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The various extrusion depths are hidden away as feature settings. This makes them difficult to modify. In a real project, where the proper extrusion depth could depend on other surfaces (rather than blind distances), it would be even harder. I'd like to control the extrusion endpoints from a sketch in the front (or side) plane, partially so I can have them all in one place, but also so I can constrain them with other things.
I know I can create a sketch on the front plane and Use some edges to get this:

Which does, at least, let me constrain future geometry based on the extrusions. But it doesn't solve the root problem of constraining, or even explicitly defining, the extrusions themselves. I can't, for example, set a dimension between the top and bottom edge – because, I guess, that would require the dimension to "go back in time."
I can draw the front sketch manually before the extrusion and then use the "to vertex" extrude option, but that seems like a bit of a hack. In particular, if the top sketch surfaces are nontrivial, I won't be able to hand draw a "poor-man's-projection." And then the front sketch loses a lot of its ability to convey intent. (A Use won't work here, because, again, that would require time travel.)
How is this typically handled? The last time I used CAD seriously was something like 7 years ago – I guess it must have been AutoCAD. Do I need to retrain myself to think differently about how models should be built?

The various extrusion depths are hidden away as feature settings. This makes them difficult to modify. In a real project, where the proper extrusion depth could depend on other surfaces (rather than blind distances), it would be even harder. I'd like to control the extrusion endpoints from a sketch in the front (or side) plane, partially so I can have them all in one place, but also so I can constrain them with other things.
I know I can create a sketch on the front plane and Use some edges to get this:

Which does, at least, let me constrain future geometry based on the extrusions. But it doesn't solve the root problem of constraining, or even explicitly defining, the extrusions themselves. I can't, for example, set a dimension between the top and bottom edge – because, I guess, that would require the dimension to "go back in time."
I can draw the front sketch manually before the extrusion and then use the "to vertex" extrude option, but that seems like a bit of a hack. In particular, if the top sketch surfaces are nontrivial, I won't be able to hand draw a "poor-man's-projection." And then the front sketch loses a lot of its ability to convey intent. (A Use won't work here, because, again, that would require time travel.)
How is this typically handled? The last time I used CAD seriously was something like 7 years ago – I guess it must have been AutoCAD. Do I need to retrain myself to think differently about how models should be built?
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NeilCooke Moderator, Onshape Employees Posts: 5,790
Hi @Maxpm please don’t set this answer as “rejected” because that is how a parametric modeller works (AutoCAD is an explicit modeller). How you explain it is correct and it’s neither difficult nor a hack. If you download the eBook “Mastering 3D Modeling” the inner workings of a parametric modeller are explained. You can also learn modelling best practises from the Learning Center or attend an essentials webinar.Senior Director, Technical Services, EMEA6
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