OK, here are some basic tests... with some interesting results.
The mask consists of:
- A WM flow map image generated from the TER
- A water mask image subtracted from the above
- A distribution shader with a minimum altitude set to remove high altitude trees (subtracted from both of the above)
The resulting mask is used for the fractal breakup of the green surface and the tree density shader. Test renders with and without trees (low quality to keep times down).
Image map only
[attachthumb=#1]
[attachthumb=#8]
Intermediate colour adjust shader
[attachthumb=#2]
[attachthumb=#9]
Intermediate surface layer (Fractal breakup = 1.0)
[attachthumb=#11]
[attachthumb=#12]
Intermediate surface layer (Fractal breakup = 1.8 )
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[attachthumb=#4]
Intermediate colour adjust shader -> intermediate surface layer
[attachthumb=#7]
[attachthumb=#5]
[attachthumb=#6]
The colour adjust shader provides the most accurate representation of the mask image. (and much better control over the image) I used to create 4 flow maps for TG0.9, but now I can replace them with a single image which is going to be a big saving in resources.
Only those examples using an intermediate surface layer have a correct object distribution! While these renders use a fairly distant camera, I suspect that the object distribution problem may be linked to the other surfacing problems mentioned in my original post (although I'd have to check). All other shaders also produced rogue trees on the surface of the lake.
[attachthumb=#10]
Hopefully the difference between these two intermediate shader types may provide the solution.. for now I'll simply use both with each image map. FWIW this also provides a good way to use a single image map in several different node branches from just a single instance.
This may have other implications for some of my other experiments (and hopefully get past some of the limitations I struck)