Volume From Contours

I am trying to find the volume of earth that must be excavated to prepare a driveway (both cut and fill). I have a .dwg file with a contour map of the site. I would like to make this into a volume, and intersect it with other volumes, using the solids tools. (The other volumes are the driveway extended upward along the blue axis, for the cut volume; and the driveway extended downward, for the fill volume.)
My problem is that I cannot figure out how to make a volume that has a top surface from a contour map. I’ve attached my attempt, at a very simple case that includes just 3 contours, at the far left in the .skp file.
Next, I used Draw>Sandbox>From Contours to make a surface (2nd from left).
Then, I placed a plane beneath the surface and extended the end of each contour downward to the plane.
Finally, I completed the projected footprint of the surface to form the bottom. I then filled the quadrilateral sides by redrawing the top edges. Finally I deleted the plane below (right).
I made a group from the structure, but the “entity info” window did not display a volume.
To the best of my understanding, the lines on the surface at the tops of the quadrilaterals should be straight on the surface, because they are edges of the (usually hidden) triangles.
The real case is considerably more complicated (incomplete contours, etc).
TX_0-TestCase.skp (149.4 KB)

TIG’s Cut-N-Fill plugin may help here. It’s over at SketchUcation PluginStore.

I think someone may also have written a command that will do this.

If the contour map is rectangular, draw construction lines down from the 4 corners. Use the Rectangle Tool to draw a face below the map some adequate distance. Then draw edges between the corners of the map and the rectangular base. (Lastly, make sure all faces are facing outward.)

I found I could use Joint Push Pull to create a volume from a contour generated surface. You end up with the same surface on the bottom, so it takes further work to chop off a flat bottom to some reference base elevation, but that’s not hard.

Here’s a first step or two that might help.
The sandbox from contours was clicked off screen. Then I used Adebeo Push Line.

The sandbox tools are designed for this. Just use drape to project the shape on a flat plane.
The edges of your shape won’t be straight as the contour isn’t straight.
There is also an issue being caused by a very small edge. If you remove that tiny edge before using by contours your shape will work without having to fill in the gap that I show here.


Many thanks Box! I got this to work up to the last step, where the edges of the surface (now halfway up the rectangular prism defined by push-pull) are used to define the cut that removes the top of the rectangular prism, and leaves the surface as the top of the final solid. For whatever reason, when I select the top of the prism as indicated in the video it selects only that face, rather than halfway down. Should I change a setting for the select tool? Or for the prism? I attach my prism before the final step.TestDrapeTool.skp (450.1 KB)

Again, Thank You Box! I got your Drape and Push/Pull technique to work using “intersect faces with model” after forming the rectangular prism but before making the cut. I then exploded the surface and re-grouped it to find the volume.

I think you are missing a few of the fundamentals.
Context being one and how the select tool works the other.

I did my gif above while inside the group created by the From Contour tool. If you look you will see the gray bounding box showing that the group is open for editing. This put the flat plane and the pushpull in the same context so they naturally intersected. You are working outside the context of the group therefore separating the geometry, which is why when exploded it creates the cut.

The select tool works in two different ways, left to right with a solid fence will select only things entirely within the fence, so as you see in this gif only the top is selected.
Right to left with a dashed fence will select anything the fence touches, hence the same action from the other side and it selects the top and sides.

There are many ways to do the same thing in SU, avoiding the need to explode things is generally a good idea, I’m not saying you never need to explode just that understanding how to work within the relevant context will go a long way to good workflow.

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