Distribution of different species of trees !

[pclavett]

I have been toying with Terragen 2 for the past few weeks after almost a year away from it and tried to devise a way of planting different species of trees without trees being planted on top of other trees ! Could not find a thread to do this except use the blendshader option with one population inverse to the other and therefore limited to 2 populations not bunching one on top of the other. I have what is now a 10 populations complex that can spread 10 different species without instances falling over one another. The included image show a standard terrain with a forest distributed according to slope only with flats free of trees (last image). The species of trees of course make no sense other then they were all in the USA east set from the xFrog library and combined these so that different colors could be seen to evaluate the spread and areas of spread. In image 1 the PF scale was probably too high with clumps of species more visible. In image 2 the PF's were reduced by half giving a more natural spread I think anf image 3 shows a higher quality render with slope effect on distribution. This looks fairly good except for the choice of trees ! A screenshot of the complex is included and I am working to make it "internalized" for ease of use. and reduce the clutter. Maybe somebody has already done this but could not find the thread for it ! Appreciate your comments ! If you know of an easier way please direct me to the appropirate thread....Thanks !
Paul

[Henry Blewer]

I have found that using distribution shaders, that this is not often a problem. The one on the top of the hierarchy 'overrules' the preceding distribution.

[domdib]

You've obviously put a lot of work into this, and the results look pretty impressive. Perhaps others who work more with populations will have more technical observations.

[bigben]

The tricky part is firstly to describe the distribution of each species and then create a mask for that...

• elevation
• degree of slope
• heading of slope (e.g. sheltered from sun = wetter = higher density/higher elevation)
• gullies or ridges...

Then you need to remember that your mask quantifies the density and not the placement.  In areas where species overlap you need overlapping masks with a reduced density.

To give a basic example, let's say species 1 has an minimum elevation restriction of 1000m with a fuzzy zone of 200m, and species 2 occurs below species 1.  Rather than try and be clever with a second elevation restriction for species 2, you could simply subtract the mask for species 1 from the mask for species 2, providing a transition in density between the 2 populations.