CAD tip # 7329:

The triplets you enter for the individual vertices of the 3D polyline are not X,Y,Z coordinates but the values of length,azimuth,slope (e.g. 123.4,20,-50 - segment 123.4m, in the 20° direction, descending 50%).

You can download the free 3DPolyC utility from Download, load it with APPLOAD and start it with the 3DPOLYC command.

Since version 1.1 of the same utility you can also use the command 3DPOLYS, which is optimized e.g. for drawing sewer lines. You will enter the initial elevation, the uniform slope (degrees, percent, promile, 1:X) and then just click the XY vertices (plan) - the polyline will draw in 3D with the given slope. The option "S" allows to change the slope also during specifying the individual segments.

If you've got standard relative angles of 3D segments (planar and vertical), you can also draw your 3D polyline using a simple script file (save to a .SCR file and run with the _SCRIPT command) with data lines in the format @segmentlength < planarangle < verticalangle - e.g.

_3DPOLY
0,0,0
@2.50<359.9<0.5
@2.50<360.0<0.0
@5.0<0.5<0.0
...etc