Tracing a bitmap in Rhino

[gregrnel]

Hey all, I'm trying to do a "correct" Fender Telecaster body by using a hi res bitmap to trace the outline. It seems that no matter how good the outline looks on the screen, there are various dips and flat spots (not perfectly round curves,as shown on the screen) when I run the file. I'll go back, adjust control points run it again and get similar results. I've tried the smooth command in various configs to no avail. Any ideas on getting great curves in Rhino? Thanks!!

[turmite]

Lay this dxf on top of your bmp and see how close it is.


www.guitarbuild.com/modules/mydownloads/


The dxf is about half way down the page. I did a copy and paste and then noticed it had the author's name and didn't want to cause any problems so deleted the dxf. The downloads are free.

Mike

[gregrnel]

Hi turmite, thanks for the reply.

I did try the specified file, and it appears to be right on, however, like the others that I have done, the same problems keep creeping up. It looks great on screen , but when I run the file I get flat spots and uneven curves.

Is it the way I'm exporting from Rhino, to Sheetcam?

for a newbie....

Here's a screen shot

Lay this dxf on top of your bmp and see how close it is.


www.guitarbuild.com/modules/mydownloads/


The dxf is about half way down the page. I did a copy and paste and then noticed it had the author's name and didn't want to cause any problems so deleted the dxf. The downloads are free.

Mike

[turmite]

I'm sorry, I thought you were trying to model the guitar in Rhino as a 3d model. I'm going to ask an obvious question, but have you emailed Les at Sheetcam? I couldn't read the screenshot, and don't use sheetcam, but I would bet it is how you are exporting from Rhino. I know that there have been times I have had to export a dxf for use in Bobcad v17 and some of the export options will not open in Bobcad.

If I can be of further service let me know.

Mike

[Bitshird]

Gregnel;
I mget the same problem in sheetcam, I've tried exporting the DFX in all versions of AutoCAD from 12 through 2004, 2004 seems to give me the smoothest radius on a curve

[lakeside]

When vectorizing bitmaps some cad clean-up is needed. I found Corel Draw is very good software for this. You can have the software do an outline of bitmap or jpeg or you can trace and save as DXF or DWG

[pointcloud]

I just did a circle in rhino saved as dxf. then opened it in bobcad... With no problems.. I use 2000 and checked entitys only dxf..
Maybe this will help.

pc

[DanC]

When you turn on the curvature graph in Rhino, how does it look? If it is the way you are exporting the dxf out of Rhino, then bring it back in on another layer and compare the original spline to the dxf file you created.

[Chris Baird]

What curve tool are you using to trace the bitmap? I often will use an interpolate through points tool and quickly trace the bitmap. I will then use the "rebuild" command from the edit menu to reduce the control points to a minimum that I find will work. I then use the "fair" command to fair out the curves and do occasional manual control point nudging. The curve analysis graph is very useful at this stage.

[machineoperator]

Try exporting as an iges. file from Rhino. If it is possible to import as iges. into Sheetcam. I have had problems with curves (splines) when exporting as dxf. and importing into Gibbscam.