The Grove / Learn / Prune

Prune

Witness branches compete for light. Drop them when too little is available. Evolve your trees into airy branching structures.

Grow feature illustration

If a tree would keep growing every branch, it would become a thick green ball soon to collapse under its own weight. To escape this horrible fate it drops all but the most successful branches. Dropping branches keeps the tree airy and allows light into the crown. This the exact opposite to space colonization and yields far more natural results at the cost of more calculation time – but staying true to nature.

Shade

Most branches are dropped because of low light. To be able to grow sensitive trees, the Grove as its very own ray tracer for real shade. It works on the entire tree and can even include an environment. The results are smooth values from light to dark, calculated for each branch. The default values work well in most situations and you should rarely have to tweak them.

Real Shade

Ray Tracing

Let’s take a look at how shade is calculated. The first thing you should know is that branch tips are the eyes of the tree, and that they are after blue sky light. This is the light that makes trees grow into balanced shapes.

Shade Preview offers you a view behind the scenes. It shows you where The Grove distributes shadow casting areas and just how big they are. You will see that it places polygons at branch ends. When a branch gets increasingly vertical, the area’s center is shifted toward the branch end, matching the placement of real leaves around the branch. The size of each area is controlled by Leaf Area.

shadetab
Above: Shade parameters have moved from the Prune tab into their own Shade tab. The eye icon enables a 3D view preview of your settings.

Shade Preview also shows the ray tracing samples. It uses a phyllotaxic distribution of samples – the same natural distribution seen in sunflower seeds and pine cones. It’s only fitting to use this optimal distribution to sample the light environment. Increase Shade Samples for accuracy and smoothness, while fewer samples will introduce randomness.

Environment Shade

You can see the effects of To Light on single trees or multiple trees growing together. But it is best visible in trees avoiding buildings or natural obstacles. The new Shade + Block environment type includes the environment’s polygons in shade calculation.

Sensitivity Gamma

The amount of shade is a linear scale from bright to dark. But as so many things in nature, reactions to linear input are often exponential. Sensitivity gives reactions to shade an exponential nature. It’s interesting to see how small changes in the gamma sensitivity yields very different tree characters. Definitely something to play with and a great new tool in the box.

Drop

Alright, we’ve calculated the shade of every branch end. Now it’s time to drop the low performers. In the Drop tab you will find tools to drop Shaded, drop Relatively Weak and drop Low branches. Each of these tools control how many branches will be dropped.

Drop Shaded

By far most branches are dropped because of low light. A higher Drop Shaded will drop more branches, as simple as that. Drop Shaded only drops young branches (without child branches). Older branches can be dropped with Drop Relatively Weak.

Note that before the Grove release 5, Drop Shaded was called Shade Threshod and its behavior was inverted. When a branch had more shade than Shade Threshold, the tree would drop it.

Drop Weak

Drop Relatively Weak is a form of self-pruning based on the health of a branch relative to that of the ongoing parent branch. Trees drop (or abscise) their least successful branches in drought and in shade. Especially shade intolerant species like pines continually drop their lower branches.

Drop Weak kicks in when the ratio of the photosynthesis of the side branch / the main branch gets below the set value.

Drop Low

Drop Shaded and especially Drop Weak will clear the base of your tree when the tree grows older. But not enough. On the forest floor, animals eat the tasty green branches of your growing tree. They can only reach a certain height. In the city, trees are pruned to a certain height so they don’t hinder traffic. Drop Low is a handy automatic pruning tool that performs its work each year. Drop Low lets you define a height up to where the base should be cleared. It gradually kicks in, when the tree grows higher than the set height. So a smaller tree will not be pruned. Only when the tree grows to twice the height, it’s base will be cleared to the full Drop Low height. Keep Thick will keep thicker branches.

Interactive Shape

manualprune

Prune and Shape

It works by drawing cutting lines in the 3D view using the Grease Pencil. Press and hold D, then click and drag to draw strokes. Then apply the cut by clicking either Prune or Shape.

The Prune and Shape tools are similar, but the long-term effects are very different. Prune realistically cuts off branches and leaves thick and dead branch ends. A handy tool for cutting off larger branches.

Shape allows more artistic freedom. Cut ends have their thickness reset and they remain alive for further growth. The ends behave as new growth, like they never were any longer to start with.

Both are fun to play with, extremely addictive, and give rise to many more tree shapes. Even extremes like pollarded plane trees and pollarded willows are a breeze.

Regenerate

When a tree crown is heavily damaged or pruned, its inner branches are once again exposed to light. The branches may still have unopened buds waiting for an opportunity like this to pop open.

Paired with the new Shape and Prune tools, trees will soon recover from the tyranny you impose on them. Gaping holes will soon fill up, all thanks to the new shade calculation!

If you want watershoots to show up, be sure to keep Drop Weak very low. Otherwise these small new branches will be dropped before they have a chance to grow. This is why most conifers do not grow watershoots.

Although watershoots are natural and usually develop after damage caused by lightning, storms and falling neighbor trees – they are a common but unwanted sight on the trunks of city trees. The extreme pruning imposed on city dwelling trees is often the cause of many watershoots. The Grove has a handy tool called Drop Low for regular maintenance of your trunks.

Next up, learn more about: Flow.