Autocad topological problem

[Boblobuilder]

Hi,
I am trying to use Autocad to construct a 3 dimensional object of a new construction site plan in order to derive existing and construction elevations. The lot is roughly rectangular and has four sides. I have defined the elevations in the Z direction at each point of interest. I initially used spline to form the topological curves along each side of the property. My hope was to form this model and slice the object in order to color code each height increment. This would allow me to easily calculate cut and fill to a high precision.
The problem is that I am having trouble getting autocad to recognize the 4 splines as one object. I've tried the region command, as well as the union command. I've also tried using pline instead of spline, but getting the slope correct is nearly impossible as of yet.
A note on my spline attempt: Autocad will recognize a spline as an object if it is one continuous and closed line. The problem with this is that the construction lot is square. When I use spline as one rectangular line, it will curve the corners.
I am beyond frusteration with this... Any help would be greatly appreciated. Thanks so much!

~Jason

 

[MikeHalloran]

AutoCAD seems to treat splines and ellipses differently from other curves on some internal level that prevents it from making automatic 'type conversions', so you have to stand on your head and spit nickels to make it do stuff that should be simple.

What I would try, and I'm not sure this would work, is to generate contour lines in plan view. I'd even extend them outside of the lot boundary a bit. Then connect the ends of elevation's contour lines with three lines on or outside the lot boundaries, connect them into a closed polyline, extrude that region by one elevation increment, repeat for each elevation, then stack all the contoured slabs on top of a 'box' of plot boundary dimensions, and do a union on the whole mess.

Then I'd use the 'slice' command to break that block into subunits with vertical sides, which I could deconstruct to get (stairstpped) elevation profiles, etc. Slice will also do a nice job of cropping the block at the plot boundaries.

Before startng, type SETVAR <enter> DELOBJ <enter> 0 <enter> to make it easier to 'go back' with all this 3D solid stuff.

Or, try Rhinoceros. The only problem I've had with it is that you have to put a dimension on something, anything, in Rhino before saving to a .dwg file, or AutoCAD will open the dwg at some odd scale. Rhino doesn't see or write AutoCAD solids, but it does understand primitives and it's orders of magnitude better and easier working with surfaces.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA