How to place a point on a 3D face with the correct Z-Value?

sbcad

Hi,

is it possible to place a point in a drawing, where the Z-Value is taken from the surrounding 3D face?

Thanks!!

Hans De Backer

Have you tried Coordinate Filters?
At the prompt for a point, enter a coordinate filter (.x, .y, .z, .xy, .xz, or .yz).
For example, enter .z to specify the Z value first, either by entering a value or snapping to a point at the desired Z-location.
Then snap a location at the desired X,Y coordinate: its Z coordinate will be ignored and replaced by the initially specified Z value.

Terry Dotson

If you were to consider third party add-ons, DotSoft's ToolPac contains several 3dFace tools including the ability to select multiple 3dFaces, then pick locations within them. The resulting point has the proper elevation where it intersects the 3dFace.

Roy Klein Gebbinck

You can create a region from the 3D face and then snap to that region with the _ZNearest snap.

Hans De Backer

Roy wrote:

You can create a region from the 3D face and then snap to that region with the _ZNearest snap.

When you have a region, you could also enable the 3D snap to intersections ( 3DOSMODE bitflag 32768 ) which allows to snap to e.g. the intersection of the region with a tracking line along the Z axis. Locking this tracking line by pressing the Shift key makes this procedure easier.
Using an Xray visual style makes it easier to see which part of the tracking line is below the region surface and which part is above: when moving the cursor to the location where the tracking line crosses the region surface, a blue cross will appear to mark the 3D intersection snap.

Roy Klein Gebbinck

@Hans De Backer
Why don't 3D entity snaps work on 3D faces?

Tom Foster

Exactly. Grrr.

Hans De Backer

@Hans De Backer
Why don't 3D entity snaps work on 3D faces?

Exactly. Grrr.

YES, spot on, absolutely right, that was also my first thought, WHY don't 3D entity snaps work on 3D faces... errrrr... neither in AutoCAD!?

A 3dFace is an old legacy entity type, (I guess) dating back from the days before the ACIS modeling engine was introduced in the dwg world.
To support legacy drawings, 3dFaces remained supported ever since, though in order to benefit from any of the ACIS modeling power, 3dFaces need to be converted to (Acis) regions.

3D snapping ( 3DOSMODE ) under the hood is using the ACIS modeler, so, to be able to 3d snap to an entity, the entity must be an Acis-based entity type.
Not only 3d snaps will become available after converting 3dFaces to regions, also all the other Acis-based goodies like union, subtract, stitching, etc...

The conversion is lossless, fast and easy: the REGION command accepts 3dFaces as input.

Although it is fast, it is not fast enough to allow on the fly conversion, while the mouse is dragged over a dense mesh of 3dFaces, to enable 3dSnap calculation...

Don't let it ruin your nice evening,
Hans

Michael Mayer

@Hans De Backer said:

A 3dFace is an old legacy entity type, (I guess) dating back from the days before the ACIS.
3dFaces need to be converted to (Acis) regions.

I wasn't aware of that.

I need 3D Faces just to recreate missing Faces from imported "Surfaces"
to be able to finally stitch them to Solids.

BTW
Don't know if these are new in v19 or always existed,
but there are some reals pearls hidden in Commandline under
Autodesk term Commands that do some real magic to corrupt
3D Geometry. Which I would like to see easier accessible.
Things like :
dmsimplifyall (reduces my IFC imports by half)
ConvToSolid (often much easier than manual stitching)
DmAuditAll

They need some time to operate but it's worth.

Joe Dunfee

@Hans De Backer said:
A 3dFace is an old legacy entity type, (I guess) dating back from the days before the ACIS modeling engine was introduced i

3D faces are still very much used in the world of modeling for cartoon animation, and when converting a 3D laser scan to a model.

-joe