I measured the slopes at our campsite in Keystone, SD and found that the highest non-grass slope I could find and still climb while just walking/running up the surface was just over 45 degrees, so I think TR is onto something there. However, 45 in-game appears less steep than stuff in reality because of the OC camera angles. Perhaps an allowance of another 15 degrees is beneficial. If I can find my drawings again, I should be able to pinpoint the optimum walking slope for the realistic lower sections.
Today I spent some time on the alternate solar rays. For each direction where I had just one, I now use 4, each offset by 5x5cm from the target position of the previous. This is not a perfect fix, but did close in almost all the long slices on basic tiles.
I then figured most of the rest of the slices must be caused by faces negative to the solar normal, so I wrote a program to separate those. Unfortunately, that had ZERO effect on the visual output when they were simply separated from other faces which might interfere with that specific mesh. I may need to attempt face normal reversal on those faces to cast a shadow from them. The problem is that any face one solar normal cannot"see" should be seen by the other 3 solar normal directions when the tile is rotated. This means I need to leave both a positive and negative normal version of that face to cast all 4 potential shadows from the sun. That sounds a bit much to me. Cracking the faces down for solar negative faces already increased the fragmentation substantially, and I am not big fan of that.
I may first try opening up the variation on the solar normal directions. That may further close in the gaps, but not all.
Again, I tested to make sure this was not a math crash, which you can easily tell by walking through the unshadowed area. If you can see your shadow, it is just lack of shadow. If it cancels your shadow, there is a divide by zero error forcing paint failure of shadows in that spot. All the unshadowed spots still have nothing more than dual face pass through causing the issue.
Another thing I noticed about the shadow engine is that it often starts drawing shadows offset from the plane casting the shadow, as if beveled. This sometimes leaves shadow faces floating in mid air so many centimeters above the face intended to be shadowed. In one of the previous outputs, I noticed three of these shadow faces made a cave with the actual faces to be shadowed. It looked really strange. While I have had some success with putting a vertical wall on the inside edges of the tile (inside the earth), this success only attempts to hide those floating shadow polygons, but does not put them back where they need to be. This seems to be some kind of error in the shadow rendering loop in the engine, and is shared by the toolset. Adjusting the position of that shadow casting object has the effect of adjusting the location of the shadow, but is not entirely corrective. It is just weird.
I've got about another hour to wait for this export set. It already looks better than the previous, so I think I will release this one for viewing tonight, as long as the larger portion are not mangled.