Summer is turning into autumn at alarming speed in my neck of the wood. As I was strolling through the city the other day, trying to imbibe the feeling, I couldn’t help notice how most of the trees were not assuming their autumn shades in a uniform way. Rather, it seemed the chlorophyle was first deserting the tip of their branches, then receding towards the trunk, leaving behind it a gradient of yellows and crimsons to green. These photos are pretty bad, but you get the idea.
This (obviously) got me thinking about how one would go about recreating this effect in Max. Assigning different mat IDs to the leaves would not work because the only practical way to do it would be to assign them randomly. And what I saw there was definitely not random.
I remembered the issue had been addressed briefly in the great “realistic foliage” thread at ronenbekerman (these kinds of tip-to-trunk gradients are not just seen in autumn trees). The question was not answered, but someone did mention soft-vertex-selections – and that got me thinking: One way to do this would be to turn a soft-selection of vertices into a vertex colour and use this as a mask between two materials.
In the event, it was even simpler. The following vertex colour mask was generated by painting the tips of a random tree black using a very large brush (to generate a nice, soft gradient).
The vertex colour map was then used as a mask to blend between two 2sided materials – yellow and green. For even more realism, one could create random variations within the yellow and the green group (all leaves here have random mat-IDs).
This was the result:
Now I wonder how one would create a three-tone gradient: red-yellow-green. Any idea much welcome.