[plugin request]

Aerilius · 17 Jan 2010, 19:53

There was an interesting question in the Google help forum:
http://www.google.com/support/forum/p/sketchup/thread?tid=67df556f6e6a6d0b

The user wants to "lock" (=keep constant) the surface or volume of an object while moving edges or endpoints. That means the other edges need to move automatically to keep the surface constant. That would be like deforming a piece of clay which has a constant volume, maybe some kind of solid modeling.

Is it doable with some of the existing plugins, or would it be interesting for a new plugin (or addition to sculpt tools)?

thomthom · 17 Jan 2010, 20:01

For surface, maybe. But solid, volume - a lot more complicated. Since SU is a surface modeller, you get nothing for free if you try to work it like a solid modeller. No more help in the API either.

Modulur does have a function to keep the footprint area constant for the buildings you create with it. When you scale one axis, it'll scale the other to keep area constant. That's what it seem to be doing.

DavidBoulder · 18 Jan 2010, 23:16

If you were using a very simple primitive (like a box) I would think you could do volume as well. Could even just bey a dynamic component.

TIG · 18 Jan 2010, 23:32

There are ways of calculating volumes but these are not so fast...
You could get the shape's 'fixed' volume value, and after moving a vertex recalculate its volume, and then scale the shape about that vertex so that its volume reverts to the 'fixed' value...
Surface are is perhaps even more complex, but if a shape has a 'fixed' surface-area then after moving a vertex recalculate its external faces total area and again scale the shape about the volume to ensure the total surface-area reverts to the fixed value...
Lots of thinking needed about scaling in 3D affecting volumes and surface-areas disproportionately....