3Dforest is a R script for 2D and 3D visualization of forest plots. I wrote it for visual analysis of fully mapped 1ha insect - plant food web, but it can be useful for modelling studies as well. For example a coleague of mine uses it for vizualizing models of plant competition in meadows, he just cuts out the trunks.
The script requires data on trunk height, DBH, crown height and crown width for each tree. If only DBH is available, the other parameters must be aproximated from it first. The script can also vizualize terrain under the forest plot.
example .Rdata file
video [8mb] showing the rgl environment in which the script works