Creating 3-D Contours

[elliot pye]

Hey,

 

Im having problems with a survey i recently completed, I have all the data points as shown in the attached CAD file but am having problems creating a surface using the points. Any suggestions?

 

Thanks in advance,

CADquestion.dwg

[lpseifert]

There are no points, just contours. Are you trying to create a TIN surface; what software Civil 3d...?

[Organic]

3D contours soudns like a nightmare.

[elliot pye]

No just really creating a surface to cut stuff with, loft and sweep don't seem to be massively accurate, any other suggestions? Its with autocad 2008

[shift1313]

i may be wrong on this but i dont believe you can cut an object with a surface in Plain AutoCad.

 

The reason loft isnt producing a very nice model is because of your curves or traces. If you zoom in to some of the corners you will see they cut back on themselves like the image below. the red line is your first red line from the bottom, the black line is something i added.

[shift1313]

while i was waiting for something to calculate i made a partial surface from your lines. I trimmed the end of the first red line where it cut back on itself and your second to last line was actually two pieces so i couldnt use it as is. I set Surftab1 and Surftab2 = 50. This means you will have 50 divisions in your x and y (not actually x and y) direction. Depending on the resolution you want you can alter this number. surftab1 doesnt have to equal surftab2. here is a quick render with no material.

[shift1313]

if you can do this with a loft you will actually have a lot more control over the final shape than with an edgesurf. Because the curves are so long in one direction but close in another it makes the fit a little funky. Loft will allow you to tell how it enters and exits your curve.

 

here is a good example of what the problem is. this is a loft. the issue is the number of "control points". Say you make a polyline containing 5 straight sections, then you make another one with 7 straight sections. it needs to loft and try to blend this and you get the "wave" look. Its especially bad when you have severe angles like at the "ridge" on your contours.

 

where did these lines come from?

[Organic]

That looks pretty good Shift.

[JD Mather]

i may be wrong on this but i dont believe you can cut an object with a surface in Plain AutoCad.

 

Sure you can - just need AutoCAD 2007 or later. Would take a bit of clean-up on these curves to get a good lofted surface though.

[shift1313]

JD, how do you cut a solid with a surface in acad07+?

[JD Mather]

JD, how do you cut a solid with a surface in acad07+?

 

See the tutorials in my signature - Slice with the Surface option.

Tips 39-41 in Tutorial 1 are very much like the OP's question.

There are other examples throughout the tutorials.

[shift1313]

interesting i have tried that before and i got an error. ill have to try it again and see what happens. Maybe I tried this in 05 and just dismissed it mentally. Thanks JD

[shift1313]

seemed to work fine for me now with swept and lofted surfaces. Doesnt work with an edgesurf though. This may not be the place for it but can you explain why.

[JD Mather]

Doesnt work with an edgesurf though.

 

With the new surfacing tools in r2007 and later the earlier edgesurf, rulesurf, revsurf, 3dmesh are obsolete. No one uses those commands anymore.

[shift1313]

i was just wondering what the difference in how cad creates the surface like edgesurf and rulesurf and why they arent "surfaces" to the program for use as slicing planes.

 

For instance you can use the revolve command on a curve and make a revolved surface, but revsurf creates a different entity that cant be used as a slicing plane.

 

Is it because the old surface tools are polygon meshes and only approximations of their original curve counterparts?

[Bowl.Spliffson]

Hello I'm trying to draw a lake bed. I have the contour lines and I've been lofting the polylines i drew to eachother. However for some reason there are a few that just won't loft. I've tried redrawing them and changing the lofting path. Does any one have any suggestions of what I may be doing wrong?

 

Also since I'm lofting each line seperate there is like 10 different lofted sections. How can I join these together?

 

Thank you

[JD Mather]

Also since I'm lofting each line seperate there is like 10 different lofted sections. How can I join these together?

 

You can't stitch them together without one of the vertical programs.

 

In vanilla AutoCAD do as one loft surface feature. You might have to simplify your splines curves a bit. If you can't figure it out zip and attach what you have so far.

 

You should have continued this discussion in your original thread. I linked this one only for information.

 

Have you done the tutorials in my signature?

[Bowl.Spliffson]

Which one of the tutorials do you think would help to make 3d contour lines?

[shift1313]

tutorial 1 2 and 3

[Bowl.Spliffson]

OK than I'll do them. Thank you so much for all the help. This site is a life saver. Thankfully there's people like you guys that actually want to help others