To classically render this in any realistic fashion, it quickly gets complex. Between the physics simulation (rather involved) and the number of triangles (trees have many branches and leaves), you're going to be doing a lot of math.

I'll emphasize "realistic" - sure, we can real-time render trees in 2025 that look.. ok. However, take more than a second to glance at it and you will quickly start to see where we have made compromises to the tree's fidelity to ensure it renders at an adequate speed on contemporary hardware.

Now consider a world model trained on enough tree footage that it has gained an "intuition" about how trees look and behave. This world model doesn't need to actually simulate the entire tree to get it to look decent.. it can instead directly output the pixels that "make sense". Much like a human brain can "simulate" the movement of an object through space without expending much energy - we do it via prediction based on a lot of training data, not by accurately crunching a bunch of numbers.

That's just one tree, though - the real world has a lot of fidelity to it. Fidelity that would be extremely expensive to simulate to get a properly realistic output on the other side.

Instead we can use these models which have an intuition for how things aught to look. They can skip the simulation and just give you the end result that looks passable because it's based on predictions informed by real-world data.