## Turbo Talk => Tips and Tricks => Topic started by: Henry Hubich on March 02, 2010, 03:03:59 PM

Title: Holes normal to a curved surface
Post by: Henry Hubich on March 02, 2010, 03:03:59 PM
The traditional method for making a hole in a TCad object is to subtract a cylinder (or perhaps a more specialized shape) from the object. Correctly orienting the cylinder is likely to be difficult if the hole must be normal to a curved surface, such as the one shown in the attached screenshots. Here's a trick that often works:

In Options|Display, enable "Draw form-building edges" -- whereupon objects in the drawing will be displayed as sets of rectangular meshes. Zoom in very close to the particular rectangle that encloses the point where you want to make the hole; enable "Workplane by facet"; click inside the mesh rectangle. Don't be concerned if there is no visual indication that you've designated this particular spot, but what happens is that the new Workplane is tangent to the surface of the target object at the spot defined by the mesh rectangle. Draw a circle there and extrude it. There's the cylinder you can use to make the hole.

EDIT: If your version supports "Auto Workplane by Face," use that instead of "Workplane by Facet." You'll probably have to convert the object to a TC Surface to make AWBF functional on a curved surface. For insurance, place a copy on a hidden layer before converting. END EDIT

The attached "Form-building Edges.jpg" shows several green circles drawn on a complex curved surface with its form-building edges made visible. "Normals to a Surface.jpg" shows extrusions made from those circles.

Henry H
Title: Re: Holes normal to a curved surface
Post by: Jeffin90620 on March 02, 2010, 05:19:26 PM
Nifty technique, Henry.

I remember a thread on the old board with the same topic that wasn't as elegant in the suggested methods.

Jeff

Title: Re: Holes normal to a curved surface
Post by: Brad Easterday on March 02, 2010, 05:37:11 PM
That's a good tip Henry. Does this complex curved surface have some friends? I'd love to see the full model.
Title: Re: Holes normal to a curved surface
Post by: Henry Hubich on March 02, 2010, 06:20:57 PM
That's a good tip Henry. Does this complex curved surface have some friends? I'd love to see the full model.

Never finished it, Brad. I was having so many problems getting the various body parts to mate correctly that I put the project aside indefinitely.

Henry H
Title: Re: Holes normal to a curved surface
Post by: Brad Easterday on March 02, 2010, 06:25:37 PM
That's a good tip Henry. Does this complex curved surface have some friends? I'd love to see the full model.

Never finished it, Brad. I was having so many problems getting the various body parts to mate correctly that I put the project aside indefinitely.

Henry H

There is a fender somewhere on my computer that didn't even make it as far as yours did. :D
Title: Re: Holes normal to a curved surface
Post by: Julian Thomas on March 02, 2010, 06:33:00 PM
Quote
...problems getting the various body parts to mate correctly...
Henry, only you could come up with a way to panel-beat into shape with a virtual slide-hammer!
Great tip, I'll use that.
Title: Re: Holes normal to a curved surface
Post by: murray dickinson on March 03, 2010, 12:12:22 AM
That's very useful, Henry.  re getting body parts to mate.  It got a lot easier with face to face lofting.  In my case it usually results in an n-sided patch being required somewhere, but it's relatively easy to make it small enough that it can be ignored.
Title: Re: Holes normal to a curved surface
Post by: Henry Hubich on March 03, 2010, 07:27:27 AM
That's very useful, Henry.  re getting body parts to mate.  It got a lot easier with face to face lofting.  In my case it usually results in an n-sided patch being required somewhere, but it's relatively easy to make it small enough that it can be ignored.

Good idea, Murray. F2F didn't exist when I was fooling with that model.

Henry H
Title: Re: Holes normal to a curved surface
Post by: murray dickinson on March 08, 2010, 11:05:46 PM
I've another method of normal-finding to contribute.  Use a copy of the surface you're working with.   Intersect a polygonal prism through the surface at any point you want a normal, you're left with a patch of the original surface.  Format the intersect product to ACIS surface|from solid and facet edit delete all except the patch on the surface you're checking.  Shell the patch, the vertex edges give instantaneous normals.
Title: Re: Holes normal to a curved surface
Post by: Jeffin90620 on March 09, 2010, 12:17:11 AM
An inventive solution, but I am having some problems with it.  Specifically, I cannot reliably draw lines along the edges of the finished object (I shelled out 0.5").

I have turned Auto Workplane by Face off; that didn't help.

Could someone explain what's wrong with this V15 file?

Jeff
Title: Re: Holes normal to a curved surface
Post by: murray dickinson on March 09, 2010, 12:51:49 AM
Jeff, you can use either 3D polylines to snap to the vertices, or WP x 3 points, the first two points being the vertices of the particular normal you're after, then a 2D line on the edge you've just defined the WP from.
Title: Re: Holes normal to a curved surface
Post by: Jeffin90620 on March 09, 2010, 03:04:09 AM
Hhmmm... I don't understand why the Workplane by 3 Points mode is necessary.  The Auto Workplane by Face mode should work, as well as the Workplane by Facet mode, but they don't.

Jeff
Title: Re: Holes normal to a curved surface
Post by: murray dickinson on March 09, 2010, 06:21:28 PM
This defines an instantaneous normal on a curved surface, which is why there isn't a planar reference.   The most accurate surface plane definition at an instantaneous normal is to use the edge as z axis.  The surface has continuous curvature, so there isn't a planar reference.
Title: Re: Holes normal to a curved surface
Post by: Henry Hubich on March 09, 2010, 06:42:28 PM
Hhmmm... I don't understand why the Workplane by 3 Points mode is necessary.  The Auto Workplane by Face mode should work, as well as the Workplane by Facet mode, but they don't.

Jeff

I think it'll work if you explode the object to a TCSurface. (Don't forget to save a copy of the Solid first.)

Henry H
Title: Re: Holes normal to a curved surface
Post by: Jeffin90620 on March 09, 2010, 07:04:53 PM
I did explode to a Surface.  Didn't help.  I expect that, even though the facets were automatically highlighting, clicking near it wasn't good enough to put the line on a plane that intersected the vertices.

Jeff
Title: Re: Holes normal to a curved surface
Post by: Darryl W on February 28, 2018, 10:49:37 PM
I know this is an old topic that Henry started but its such a valuable topic I could not resist and hope that nobody minds.

So this topic and the attached images that Henry posted is exactly what Im hoping to achieve, essentially I want to model an old cars complete body ( biting off more that I can chew, oh well ) and the inspiration for this idea came from Henrys post. So my main question atm is which tool should I use to start creating the profile. Should I use the bezier curve, 3D polyline or other, cos Im not sure which one to use?

If I use say a 3D polyline tool can you do some of the design in world plane then switch to say sw plane whilst still drawing?

I did read in one of the lofting posts from a general discussion that you can loft the profiles, but how can that be when the actual design if you like of a fender / guard is essentially just a shaped ( pressed ) surface. Can someone point me in the right direction with a simple overview of the right tools to use and a start pointing in the process?

Title: Re: Holes normal to a curved surface
Post by: Henry Hubich on March 01, 2018, 08:31:30 AM
I know this is an old topic that Henry started but its such a valuable topic I could not resist and hope that nobody minds.

So this topic and the attached images that Henry posted is exactly what Im hoping to achieve, essentially I want to model an old cars complete body ( biting off more that I can chew, oh well ) and the inspiration for this idea came from Henrys post. So my main question atm is which tool should I use to start creating the profile. Should I use the bezier curve, 3D polyline or other, cos Im not sure which one to use?

If I use say a 3D polyline tool can you do some of the design in world plane then switch to say sw plane whilst still drawing?

I did read in one of the lofting posts from a general discussion that you can loft the profiles, but how can that be when the actual design if you like of a fender / guard is essentially just a shaped ( pressed ) surface. Can someone point me in the right direction with a simple overview of the right tools to use and a start pointing in the process?

Some suggestions, Daz...

Model one component at a time: front fender, rear fender, hood, etc.

Use Splines for the profiles. Start by drawing the one you guess will be the most complex. For the remaining profiles, use copies of the original, relocated and edited as necessary.

If the profiles are all open curves, the resulting Loft will be a "sheet object" with zero thickness. You can impart a nonzero thickness if the loft is smooth.

Henry H
Title: Re: Holes normal to a curved surface
Post by: Darryl W on March 05, 2018, 04:22:22 AM