I'm thinking that while randomly generating each instance of a plant might be too big a job for Terragen to do, even just having it able to randomly generate the original and then instance it all over the terrain would go some way towards making things more realistic. It could give people more control over what style and complexity of plants they want, and avoid the problem of people looking at other people's images and saying 'Oh, you used such-and-such a plant from so-and-so's website!'. Besides, with multiple populations on top of each other, the visual effect could come quite close to that of having each plant procedurally generated (at least for certain scenes).
QuoteTo be perfectly honest, if there were a way to just vary hue and brightness for a percentage of an object's instances (thinking particularly of trees), I think that would increase the realism immediately by a significant factor.
What I think would be even better for the realism of plant populations is to have size shaders. So that, for example, you can set a distribution shader to end the trees a certain way up a mountain, but then you can also use another shader to make the higher-altitude trees smaller than the lower-altitude trees (or vice versa, although that would look a little strange). If this capability already exists in the program, I haven't heard of it- nor have I seen any sign of people using it.
