Odd behavior using Trim command
Shessar
🖼️ 33 images Surveyor
I am just getting back to using CC3+ after a couple years of being away so my memory of the commands may be wrong.
I trimmed the length of a river (spline) and wanted to use node edit to shift the end node down some. However, when I try to click the end node it acts as if the trimmed part is still there. I turned on frames to see what the heck was happening and Frames showed that the trimmed portion still existed.
Either Trim isn't really removing the part that I trimmed, or I'm not understanding how it should work.
See the image but forgive the size since this was the only way I could get the Frame to show.
Comments
Splines in CC3+ are a little funny. The frame of the spline is always there. CC3+ defines a parameter what runs from 0 to # nodes that goes from the start of the frame at parameter=0 to the end of the frame at parameter=# nodes. What TRIM does with splines is to tell the system to start and stop evaluating the parameter at some value "t" between 0 and #nodes, which causes the spline to shorten. As you have done here, showing frames will show where the nodes that you can select are. If you use LIST on the trimmed river, you'll see that the "start parameter" and/or "end parameter" are values other than integers.
This behavior is caused by the mathematical underpinnings spline definitions. If you convert the spline to a path using LTP2, there will be a lot more nodes in the path, but TRIM will cut out things and you can select exactly on the end of the path as you were expecting.
Trim does this when operating on splines. The reason is that the shape of the spline is dependent on the positions of the nodes, including the following nodes, so if you simply cut it and placed a node at the end, the shape would change.
Since CC3+ is a CAD program, having the rest of the shape change shape isn't really acceptable, so instead when you trim a spline, it just hides the rest of the shape instead of removing the nodes from the entity.
Perfect explanation gentlemen! So, if I do a 'smooth to straight' then trim again it should remove the unwanted part, right?
So that is what happened !
I trimmed the frame to, after I trimmed the spline.