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I think OpenSCAD desperately needs some kind of anchors. E.g. how does one place a sphere on top of a box? First you instantiate a box, then you calculate the

by _flux 5y ago

I think OpenSCAD desperately needs some kind of anchors. E.g. how does one place a sphere on top of a box? First you instantiate a box, then you calculate the center coordinate of the sphere and instantiates that one. If you have many objects touching each other, you're going to have a lot of maths there with a lot of variables or functions to reduce repetition. A better way in my mind would being able to express things like "sphere of radius R has its bottom at center of box.top". Not even a constraint solver is required for this, though that could be nice as well, but would probably introduce its own set of problems :). This kind of thing could be particularly nice with the interactive OpenSCAD editor that would enable quickly visually determining the locations of the anchors.

dTal 5y ago
A thing that can understand "sphere of radius R has its bottom at center of box.top" is exactly a constraint solver, so I'm not sure what you mean by saying it's not necessary for that to work. You have constrained R, and the location of a particular point, and the free parameter - the center point of the sphere - must be calculated from those constraints. And if you don't want the sphere to be exactly in the center? Suddenly you have only constrained 1 out of the 3 axes of the centerpoint, and will need additional constraints to disambiguate the shape. Or what if you want to fix the centerpoint and have the radius vary?
- _flux 5y ago
  Both objects would have certain fixed hook points, such as bottom/right/center/etc and then the equation is as equality of exactly two of those points (new points could be derived from the existing ones, to express "1 mm Z from top"). So yes it is a constraint solver, but a very simple one, as you can constrain only one parameter, but all others would need to be provided; I meant R to be such a provided value (can of course be a parameter to the function creating the object). Perhaps you could also implement is in a way that R can be provided but expect the code to provide all others. A more general solver would be nice, but they don't seem trouble-free either. But sure, the syntax could be geared towards future development of such a solver. Maybe there could be a particular syntax for invoking such a solver that would fit well with the existing system, e.g. an "object" that only has hook points that could be constrained in various manners, and then actual objects would use them as input coordinates.

by _flux 5y ago

dTal 5y ago

A thing that can understand "sphere of radius R has its bottom at center of box.top" is exactly a constraint solver, so I'm not sure what you mean by saying it's not necessary for that to work. You have constrained R, and the location of a particular point, and the free parameter - the center point of the sphere - must be calculated from those constraints. And if you don't want the sphere to be exactly in the center? Suddenly you have only constrained 1 out of the 3 axes of the centerpoint, and will need additional constraints to disambiguate the shape. Or what if you want to fix the centerpoint and have the radius vary?

_flux 5y ago
Both objects would have certain fixed hook points, such as bottom/right/center/etc and then the equation is as equality of exactly two of those points (new points could be derived from the existing ones, to express "1 mm Z from top"). So yes it is a constraint solver, but a very simple one, as you can constrain only one parameter, but all others would need to be provided; I meant R to be such a provided value (can of course be a parameter to the function creating the object). Perhaps you could also implement is in a way that R can be provided but expect the code to provide all others. A more general solver would be nice, but they don't seem trouble-free either. But sure, the syntax could be geared towards future development of such a solver. Maybe there could be a particular syntax for invoking such a solver that would fit well with the existing system, e.g. an "object" that only has hook points that could be constrained in various manners, and then actual objects would use them as input coordinates.