Creating Rods

[John_M]

I am using VW 12.5 (Fundamentals, RenderWorks). My need is rather limited - to create rods of a specific diameter and length and export IGES files for use in another program. The rods can have different cross-sectional shapes. What I am given are 2-D (filled) plots of the cross sections.

I import the image and then use Modify/Trace Bitmap. The resultant trace is usually pretty good. I can successfully create the extruded rods, but the other program that imports the file requires that the object have one surface in its geometry object tree (other than the front and back trim surfaces).

I have experimented with editing the trace using various combinations of Model/Extrude and Modify/Convert to Polygons, Modify/Group, Modify/Combine into Surface. If I create a geometry by various combinations of the above means, the result has a large number of surfaces, I guess one for each vertex in the original 2-D trace.

So how do you combine things so that the result is all one surface and not a large number of individual connected ones?

Thanks.

[Pat Stanford]

Check the Modify Menu for Compose. This will only work is you have objects that are exactly coincident at their end points.

Even better when you are doing the tracing why don't you use the Polyline tool. It will do both lines and curves and create one object. The version in VW2010 has some really great features for tracing.

You should also take a look at the Combine/Connect tool as it can do some of what Compose does and will also extend lines so they are coincident.

[John_M]

Thanks for the suggestions.

If I use Modify/Compose on the bitmap trace, then extrude, it still gives multiple surfaces. Is there something else I need to do before or after using it?

I had tried the Polyline tool already, but the automated Trace Bitmap gave much cleaner traces than I could make by going around the object by hand. I just made up a quick shape by hand using Polyline, extruded and saved as IGES. It does indeed import into the other program as a single surface (plus front and back trim), which is good. Any hints on getting better traces, i.e. closer match to object, would be appreciated.

I looked into the Combine/Connect tool as you suggest but frankly don't understand how to apply it in this case. The hint says "First click an object's end point. Then click on the boundary." Not sure how that applies here.

Thanks.

[Benson Shaw]

Hi, John - I do a lot of tracing of photos for export to dwg and eventually a cutting machine. I gave up on the trace bitmap because it often interpreted a line or edge as a band, or did a really close switchback which looks like a single line, or made stacks of lines, etc. I'm glad to hear someone has made it work!

Gaps in the perimeter may cause your extra surfaces (guessing here). Even one gap may cause confused surfaces. You could find gaps by making an offset of the source poly if it doesn't have big undercuts, or by scaling a copy of it waaaaay up. Or by zooming in to each vertex and moving it with the 2d Reshape tool.

The Connect/Combine tool has several modes. The Dual Object Combine Mode will create a single polygon from two disconnected linear objects. The other two modes leave two distinct, but touching objects. This tool will not close a poly with one gap.

The "Close" checkbox in the OIP for a polygon will fill the last gap. (but no such checkbox for polylines).

The 2d Reshape Tool also has a useful mode - Show Hide Edges. This will toggle an edge in a polygon or polyline object. The new one works on polygons and polylines, I think the VW12.5 one only works on polylines, but not sure.

All the above probably means lots of zoom and unzoom, which might make the hand trace more attractive. Hitting the QWSD keys will toggle the usual constraints which makes tracing much easier - for some segments you need them on, sometimes not.

Good luck!

-B

Edited June 26, 2010 by Benson Shaw

[islandmon]

or use a vector program like Adobe Illustrator or the wonderfully free Inkscape to convert those profiles to vectors and then export as DXF or EPS prior to import into Vw12.5.

[Pat Stanford]

It is likely that the lines created by the Trace BItmap do not have coincident end points. When you do Compose, it makes polys of the ones that do.

So, Compose, zoom in, adjust the end points to be coincident, select, compose.

Lather/Rinse/Repeat.

Depending on the complexity of the trace, this could be a really long and aggrevating process. Tracing with the polyline tool is often easier. Or is they are simple, draw surfaces (rectangles, arcs, circles) and then use the Add Surface command.

No chance of getting the profiles in a different format that is vector based?

[John_M]

Thanks for all the replies so far. I have tried the polyline tool and as suggested it seems to do the trick for creating extruded objects that turn up as a single surface (aside from front and rear trim surfaces) in the other program.

A few more questions please:

1. Can someone recommend a tutorial on tracing with the polyline tool? I'm used to using the pen tool in Photoshop and none of the polyline modes seems to mimic that. I'm finding I have to use the Arc Vertx mode and move in small steps. If I use the Cubic Vertex mode, I can cover a lot of distance with the first three points that I lay down, but then when I proceed with the next point all the preceeding curves start to change - I just don't get it.

2. After completing the trace with the polyline tool, I would like to smooth things out just a little bit to correct for small hand tracing inaccuracies. Modify/Poly Smoothing seems to make too gross of a change. Are there options to control how much smoothing these do?

3. Finally, I still don't want to give up on Trace Bitmap. For my types of images e.g. a black circle on a white background, the result of Trace Bitmap is a very clean, smooth trace, much better than I can do by hand with the polyline tool. As far as I can tell there are no gaps. Can someone please explain a step-by-step procedure for converting the result of Trace Bitmap to the same kind of object I get when I use the polyline tool?

Thanks again.

[Pat Stanford]

1. VW2010 has a new mode in the polyline tool called Tangent Arc. It makes tracing much easier.

3. I thought I had given you a step by step.

A. Trace Bitmap

B. Select all the objects drawn by the bitmap and Group them (if they are not already a group) and then do Edit Group. This will isolate the lines created by the Trace Bitmap and make it easier to do the next steps.

C. Select All (inside the group) and do Compose. This will make polylines out of all the objects that have coincident end points. This should leave you with a mixture of lines and polylines.

D. Select and object and zoom in close on the end. Find the line that "looks" like it connects to the end of the first object. Select it and do one or more of the following:

1. Manually move the end point so it is Coincident with the end of the other object (make sure you have the end point snap [and probably only the end point snap]) turned on.

2. Select both objects and use the

3. Use the Combine/Connect Tool in Dual Object Combine Mode to connect the objects.

4. Use the Trim tool to delete extensions back to other lines.

5. Use other tools as necessary to make sure the end points are coincident.

E. Select all the objects and Compose.

F. If you did not get all of the objects correct, repeat steps D and E until you have one single object.

[Benson Shaw]

I am curious, too, about working with paper(?) plots. If those were generated by something digital, maybe the vectors from that source would be available to you.

Anyway, if you are finding the poly editing too coarse, adjust and toggle your snap (constraints). Sorry to repeat if you already know all this:

If you need the snap grid, set the spacing to something useable (dbl click the Grid constraint button or go to Document Settings in Doc Prefs/Setup). I usually turn off the grid snap and leave it off.

Moving a vertex or control point with all snaps off provides very fine control. Turning the snaps back on allows alignment with smart points. The snaps I usually need are Object, Intersection, Angle, Smart Points. Toggle these snaps on and off as needed with their hot keys - qwsd. Snap Grid hot key is: a

As for controlling the curved segments, you might want to look at fewer, rather than more points. Delete or add vertices with the 2d reshape tool (change modes with the mouse or the "u" key. Also, I find that Cubic Spline curves are not acceptable to some end users, so you might be stuck with tangent, or at least connected arc segments. Ask the end user.

Use the mouse or u key to toggle thru the various vertex modes while you are drawing a polyline. For example, you can start a polyline in corner mode, after a few clicks, hit the "u" key several times to activate the Arc mode (watch the mode bar to see the mode change), draw an arc point or two, hit the "u" key several times to return to Corner, etc.

Post again if things are not working for you.

-B

[John_M]

The image files that I work from are raster-based, not vector.

I turned off the snap options and that helps a lot with the polyline tool. I also learned to use some of the vertex editing tools which should be useful also. I think using the polyline tool that I can do what I need to do - the resultant extrusion shows up as one surface when the IGES file is imported into the other program I am using. Thanks again to all for the help.

But coming back to Trace Bitmap again maybe for the last time as your patience may be running out...It's inviting to use this as it is automatic and fast. I don't understand all the potential issues that people are referring to. Keep in mind that the images I am working with are very clean JPEG's e.g. a filled black circle on a white background. The result of Trace Bitmap is a set of vertices with connecting curves - no gaps, no extra lines and it all seems to be one "object." So it doesn't seem all those editing steps referred to above should be necessary. If I highlight all the vertices and do Modify/Compose, the inside of the ellipse gets filled (covering up the grid behind it) and it appears to be one simple object.

However, extruding and exporting as an IGES file results in multiple surfaces in the other program's geometry tree. It looks like a separate surface for each segment between the vertices.

[Pat Stanford]

Can you post one of the images you are trying to trace? Click the Switch to Full Reply button and use the File Manager. It may help us to come up with a better solution for you.

You say that the Trace Bitmap works well, but obviously it isn't or you would not need to ask so many questions. ;-)

I believe (not sure) that Trace Bitmap only draws lines. Even though the lines may look like the ends are coincident, they are not or the Compose would put them all together. Zoom in about 20,000% with Zoom Line Thicknesses off and you should be able to see the problem. It does not take much of a difference to throw off Compose.

After you do the Compose, take a look in the Object Info Palette and see how many objects are shown. If they all connected then there should be only one. If there are multiple then some end point was off and you need "all those editing steps" to get it right. (I am just being a little sarcastic here. Not insult intended ;-)

If you get a single object after the compose then you should be able to extrude the object to get your rods.

[John_M]

You may have just said the magic words - that you believe Trace Bitmap only draws lines! I confirmed your suspicion and that could be a show stopper for my application. Why didn't you say that before? :-)))

However, since we've gone down the road this far, I'd like to follow through - if I import a high enough resolution image and generate a lot of vertices, it could still work.

After Trace Bitmap, I zoomed in all the way with Zoom Line Thickness off and it appears the line ends are indeed coincident. After I do Compose, the Object Info Palette just says "Polygon" i.e. one object.

I will post a couple of example images.

> If you get a single object after the compose then you should be able to extrude the object to get your rods.

Just to clarify again, I am able to extrude the object to get a rod. It's just that the IGES file shows up in my other application as a collection of many surfaces, not one.

[Pat Stanford]

If the IGES export is not working correctly that could be a limitation of the IGES format.

In a new file draw a rectangle and extrude it. Export it via IGES and see what happens on the other end.

The other thing to try would be to take the extrusion and convert to NURBS and see if an IGES export of that works better?

[John_M]

As suggested, I used the Rectangle Tool to draw a rectangle, extruded it and exported an IGES file. In my other program, it imports as six surfaces, one for each side. (I tried with and without the "Export Solid as Trimmed Surface" box checked - no difference.)

I tried converting the extrusion to NURBS and exporting, same result - six surfaces.

I can delete the front and back surfaces in the other program's geometry tree, but the protocol there requires only one surface for the rest of the rod.

We may be focusing in on the real issue now. It appears there was no problem with the result of using Trace Bitmap (other than the potential limitation that it draws straight lines) as even a simple extruded rectangle has the same multiple surface issue.

Unfortunately, the only other format the the other program will import is STEP, which does not appear to be an option in VW 12.5.

So if I use the Polyline Tool to create an object, extrude and export as IGES, I get the desired single surface for the rod. If I just create a simple polygon with one of the drawing tools, or if I use Trace Bitmap, I end up with multiple surfaces - in the latter case, apparently one for each segment between vertices.

There is some fundamental difference between these ways of creating a geometry, as far as the IGES format is concerned. Any insight would be appreciated.

[Pat Stanford]

It is definitely sounding like a limitation in the IGES file format.

The IGES is breaking anything with a straight edge into a separate surface.

Try this.

Use the POLYGON tool to draw a three rectangles.

Go to Modify and choose Polyline Smoothing and set each of the rectangles to a different smoothing mode.

Export that and see what you get.

My guess is that you will have to convert all of the vertices to something other than a corner point. Maybe to Arc Points with a very small radius will work best.

[John_M]

Will do next week when I'm back at work.

Have a nice weekend and thanks for your help.

[John_M]

Looks like you are correct about IGES and straight edges.

First, I created a rectangle using the Rectangle Tool, extruded and exported as IGES to confirm that multiple surfaces were created. Then, as suggested, I created rectangles and tried the three Poly Smoothing options. These didn't seem to do anything to the rectangle and I still found multiple surfaces.

2D Reshape Tool/Change Vertex didn't seem to work with such rectangles either, so I created a rectangle using the Polyline Tool and confirmed that it also led to multiple surfaces. I then modified the corners by using Arc Points - it was crude as I have never done this before - but after extruding and exporting I found that it was indeed one surface.

So if I trace in all my geometries using the Polyline Tool in Arc Vertx Mode, hopefully I can avoid the multiple surface issue.

For completeness - I also found that Poly Smoothing did affect a Polyline-created rectangle and led to a single surface. The amount of smoothing is excessive, however, with the rectangle turning into an ellipse. Is there an option somewhere to control the amount of smoothing?

Thanks again.

[Benson Shaw]

Just another idea.

I wonder if the 2d fillet tool in the trim/extend mode (3rd one) would help. Set a small radius in the options box and apply to all corners, then extrude (or edit an exist extrude source with the fillet tool).

A rectangle is converted to a polyline when 1st corner is filleted. Each fillet ads an arc vertex. I can't tell about the surface count of extruded result. I extruded and exported IGES and imported (in VW2010). Import produces a generic solid. VW does not reveal vertices or surface info.

-B

[John_M]

Yes, that seems to do the trick. I tested on a rectangle drawn using the Rectangle Tool and one drawn using the Polyline Tool. In both cases, the rectangles modified using the 2D Fillet Tool showed up as one surface in the IGES file (in addition to front and back trim surfaces, which are easily deleted in my other program) whereas without using the tool they had multiple surfaces - one for each side of the rectangle.

The 2D Fillet Tool is also a much easier way to round off corners compared to what I had been trying to do.

Thanks for the suggestion.