Hello, I'd like to snap the polygon of the image to the ground by rotating around its center axis -in this case at the botton of the polygon- but snapping options don't work. Snapping do work with translation but I need with rotation. Any help? Thanks

You probably mean 3 point rotation known from cad soft? I dont think there is such tool built in xsi.

Yes, I've just seen Autocad tip "Rotate One Object to Match Another" and that woul be great. I cant believe there is no such tool in SI... Thank you!

It could be done with a direction constraint. Snap 2 nulls to the end points of the edge you want to rotate around, and snap a third null to a point of the object that's supposed to be on the floor.

* make a direction constraint on one of the edge nulls, pointing to the other edge null. From the constraint property page, pick the third null as the upvector object.
* parent the object under the null that has the constraint
* move the third null, snap to floor

Thank you, rray! I will try your advice.

Sorry, but I still couldn't make it. I'd like one object snap to other by rotating. I'm posting an image with a simpler example.

The second problem you posted is more complicated and can't be solved that way (Built-in snapping tools can't do it either)

First problem you posted however can be solved using the steps I posted before.

Sorry. I was looking for a solution to the first and second problem. A rotation snapping tool or plug-in, something like that.

The second problem would require intersection snapping, which Softimage doesn't support (You'd create a circle and snap to the intersection of the circle and an edge)

Yes, both first and second problem would be easily solved with a intersection snapping while rotating tool. However, Softimage does support intersection snapping while translating. Am I wrong?