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Author Topic: Question about instancing ForestPro objects  (Read 2853 times)

CQ1841

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Question about instancing ForestPro objects
« on: May 07, 2010, 02:16:22 AM »
When you choose a FP object as your geometry, it it reading it as a single collapsed mesh, or as an assembly of instances? For example, if I made a tree with the main trunk and branches, and used 3 variations of branches with leaves and placed them on the tree, all using custom placing in Forest Pro, could I then use that FP object in another FP object to scatter it, and would it maintain the fact that i only have a trunk and 3 branch+leaf objects? Or would it read the whole thing in as a collapsed tree, thus loosing the advantage of using instanced branches in the first place :(

iToo

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Re: Question about instancing ForestPro objects
« Reply #1 on: May 07, 2010, 05:29:16 PM »

Forest handles all geometric objects as a collapsed meshes. But really, although the plugin would to preserve the instanced branches, there are not benefits doing this, because all scattered objects of a same type are identical for the renderer (they are instances).

Why do you want to preserve the instances hierarchy, to create diverse samples of a same tree or something else ?

On the other hand, you can use a Forest object as source geometry for another Forest object, setting the Display->Mode parameter of the inner object to "Meshes" (the default value is "Auto"). There is a grass sample scene using this technique in another post in the forum.

Carlos Quintero
iToo Software

CQ1841

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Re: Question about instancing ForestPro objects
« Reply #2 on: May 08, 2010, 02:46:20 AM »
Here is a better explanation:



Forest Object1, if collapsed to a mesh, might be ~500,000 polys. Now if Forest Object2 has 1000 instances, is it instancing 1000 x ~500k trees, or 1000 x (4 x 10,000 poly objects)? The latter would be a lot faster and far more memory efficient. In other words, if you choose a Forest object as geometry, does the information come through about the instances, or is it read and rendered like a regular mesh?

iToo

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Re: Question about instancing ForestPro objects
« Reply #3 on: May 08, 2010, 09:58:55 AM »

It's the same. No matter what Forest do, because the renderer always converts the Object1 to a mesh before rendering start.

But, the process is a bit different, because the renderer doesn't create the Object2 as 1000 x n polys. It only stores a reference for each tree (which requires little memory), and uses the mesh of Object1 when it needs to check the geometry.

So, in both cases the memory impact is identical: 500,000 polys. All renderers that uses instances work this way (Mental Ray and VRay).

Carlos Quintero
iToo Software