OK, so by now you're probably thinking that this is still looking a bit too chunky to be real... and it is... but as I said, the high res masks take a lot of work to prepare. This next test is another memory test to see what happens when I add a second high res mask to the project (and removing the south island blue marble image)... The render consists of just the terrain (no fractal detail), two masked surfaces for water and dry grass and because the snow was at the bottom of the node network I left it in as well. The grey bits are to be filled with sand, rock, green grass and forest.
The start of the render was promising, with memory usage still around the 1.4Gb mark, but this gradually crept up to 1.8Gb 1/3 of the way through at which point I went to bed. That's not going to leave me enough RAM for billboard and poly trees so I'll either have to try and make do with a single high res mask or split the tgd into two components at the end, one for the approach from orbit (minus objects), and one for camera angles within the central terrain (minus bathymetry image, outer terrain, island terrains etc....). I'm leaning towards the latter mainly because I want to have some overlap between some of the masked regions
The water surface in this contains no fractal breakup to keep it looking relatively blurred, although it needs an additional colour to shift the shallowest water closer towards a sand colour (easily done). The dry grass layer consists of a surface layer using a boolean style BW mask (only black and white) for the fractal breakup to control the surface distribution, a power fractal for the light colour as the input and another power fractal for the dark tone using a tonal version of the distribution mask as a blending shader. If further disguising of the last mask is required at closer camera positions I'll multipy it by a power fractal with high/low values of 1, 0.7 respectively
This is getting back towards looking very cool again
Running a render
at the border between the high and low res masks of the same view from the tgd used for the orbital render to demonstrate the difference in resolution.