Finally! After two days of fidding and failing over a hundred tries, multiple exchanges with David, Bob, and some others, and a great deal of frustration, I figured out how to do sloping-bottom pockets bounded by an arbitrary shape, instead of just rectangular slopes. It requires both features in CamBam, and a little 'wet-ware' (human intervention).
The method uses the Curved Surfaces Generator, choosing the Flat Surface option.
The C.S.G. plugin uses a polyline corresponding to the SIDE of the slope (not one end or the other) to describe a sloped rectangle. It can only generate a slope from Z=0 down to a desired depth along the polyline chosen as the starting element. (I consider that a deficiency I'll fix, if given the chance.)
Choose a polyline length, and a 'width' setting sufficient to cover your entire bounding shape. Set your depth. In my case, I wished to go from Z=-0.5 to Z=-1.5, so I had to ask for a depth of -1.0. It will generate a sloped rectangle with engraving lines to cut that rectangle. If you choose 'generate MOp', it will also create an engrave MOp with all those lines described in the correct order - with NO optimization and zero depth-of-cut - to properly engrave the rectangular pocket with a sloped bottom.
But that doesn't solve the bounding issue. Next you have to do a few simple 'wet-ware' manipulations. The bounding shape must be a closed polyline.
Wet-ware:
First, move the entire body of engraving lines down to the desired starting depth. Numerical Move will do that. For my example, I had to move the array down in Z -0.5".
Wet-ware:
Next, check the position of the rectangular array with respect to the alignment with the edges (extremas) of your bounding shape. The edges of the array change depending upon the type of cutter chosen in the plugin. If your polyline describing the slope is the correct length, and the width is 'enough', then it will generate the correct pattern for any given tool profile selected in the C.S.G. menu. You really shouldn't have to do this step, but you know you will do it! If you don't like it, you can move it. It turned out OK for me.
Wet-ware:
Next, select the entire body of engraving lines, and select 'Edit/Trim'. Hit Enter to use your engraving lines as the object to be trimmed, and select your bounding shape as the 'trimming object', then Enter. Then select to 'discard (O)utside the bounding object', and Enter again. It'll take a while on a deep pocket. Fortunately, the 'trim' feature doesn't require actual intersections (contact at XYZ) of a line and the bounding shape. It only relies upon crossing the same XY coordinates to determine where to cut the line segments. Again, it'll take a while on a deep, fine-resolution pocket.
When it's done, you will have a NEW set of engraving lines - still in proper depth and sequenced milling order - that will mill a sloped pocket within your bounding shape.
Final Wet-ware:
Select your Engraving MOp for the original rectangular slope, and completly delete all the primitive IDs in the list (triple-click in the list and press Delete). It will then give you the option to select IDs. Select your entire body of trimmed lines, and hit enter. Those IDs will replace the originals in the MOp. If you have a VERY long list of them, the primitive IDs will NOT show up in the MOp (bug), but they'll still be there. Again, this step may take a while to execute.
You now have a MOp that will generate a pocket of arbitrary XY shape with a sloping bottom.
Final advice on generating g-code: CB ran out of memory trying to generate the g-code for two such fine-resolution pockets on my computer. I killed every application that was running except CamBam, and ran it again. It got through the process. It just needed that extra 4.5Gb of memory the other apps were using.
Lloyd