Topic Title

Excerpt from the manual with my problem noted in color:

ADDING VOIDS TO POLYGONS AND SLABS | 489

�� To add a void:

1. Draw a primary polygon or slab (the polygon or slab you will be adding a void to). Use Plane Snap, Elevation/New Elev., or Edit Plane (in the 3D Views menu) to bring the primary polygon or slab into the zero plane
before adding voids. When you create both the primary and void
polygons or slabs without changing the view, they automatically lie in the
same plane. I don't find this to be true. The void is not drawn in the same plane even if the view is unchanged (of course the original inclined slab need not be drawn in a view perp to itself).

2. Draw the void polygon or slab inside the primary polygon or slab in
exactly the same plane, at Z-base (or whatever Z elevation you drew the
primary polygon or slab at) equal to zero. Rather than being drawn in the same plane as the original the void is drawn taking the unchaged z base and z height as governing, and thus it is drawn out-of-plane. You can draw more than one void polygon or slab at this time. Make sure the void polygon or slab lies completely within the primary polygon or slab.

I think some confusion reigns here, particularly with Z and the views. If you are making a horizontal slab in a front view you can nominate Zb Zh a say 0 and 200. BUT. What is really going on is that you are really making a vertical slab that is 200 thick. The problem now is: where is it in plan? You can be sure it won't be where you want it to be. I have never gotten to the bottom of this. I just draw it, go ortho, and move it to where I want it to be. This doesn't actually happen much as I work with polygons on plan.

If you make another to punch a void, using the same Zs it WILL be in the same plane.

If you come along later and "Identify-Set all" on this slab the Zs will change to reflect Zb Zh of the slab as it stands in PLAN. Ergo, if you are going to work this way it pays to do the slab and all the voids at the same time, then all will be well.

I guess this is why people prefer to work on plan and tilt-up. There are less Zs to worry about and stuff is pretty well where you want it to be.

Everybody develops their own way of doing this.

Thanks, Nick. I think I get most of your drift, though it seems to be speaking more to flat rather than inclined slabs, which are much more of a problem to me. I'll try to use what you offer.

inclined slabs, which are much more of a problem to me.

Hah! Now that's interesting. Hers's me, on of the 3D gurus round here, and you will be amazed how rarely I have had to do that. I think it's got something to do with the lack of chimneys.....

I recall that plane snappiong is the answer. I will have to get up to speed on that.

Yes, plane snapping is a way if one needs to add the void after leaving the slab production stream, but one is supposed to be able to add them without resorting to plane snapping if one does it in sequence with the inclined slab creation.

When you create both the primary and void
polygons or slabs without changing the view, they automatically lie in the
same plane.

I think not. Otherwise their would be no need for PlaneSnap.
When you do an inclined surface, the only thing that determines the inclination are the Zs of the points you are snapping to. Having the appropriate points for the void-making entity all aligned up in Z for that to be in the same plane as the master polygon, is too much to expect.

My first post should have noted that material quoted from the manual would be in black and red and my prob noted in dark red. So the manual says that the prog will do what you say we cannot hope that it do. You may be right, but I think if it has just created the inclined plane it could easily have the defining params in hand when asked at the next command to do something with them again.

(My apologies if this is an 11.05 issue resolved in 11.07.)

From the manual only:

�� To add a void:

1. Draw a primary polygon or slab (the polygon or slab you will be adding a void to). Use Plane Snap, Elevation/New Elev., or Edit Plane (in the 3D Views menu) to bring the primary polygon or slab into the zero plane
before adding voids. When you create both the primary and void
polygons or slabs without changing the view, they automatically lie in the
same plane.