Scatter stuff in space!

Content:

A Blender scene with 2 geometry node setups to scatter instances in a 3D space. There are two models, quite similar trees: the first is a rather classical emission from a surface. The second includes the new added volume (voxels) functions. The second may have a significant cost (I didn't test it further).  These setups are well suited for still pictures. It's not animation ready, although it is It might be possible: using the time function to add spin and drift to the instances. Since the simulation nodes are coming soon with Blender 3.5, I let it be like that.  

I have been using those rocks and debris many times for my sci-fi pictures. 

Blender version is 3.4.1 and more. 

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How to use it:

Choose your method (plane and volume are linked to their respective Geometry node setup, starting from a plane of volume is only about the result you want to achieve, the node tree is almost the same.

Then move up the selected instances you want into the Selected_Rocks or Selected_Debris collection. They will be randomly scattered.

Note: If you want an instance more frequently than others, duplicate it the appropriate number of times to increase its probability (so far, I can't make a proper node for this) and add it to the same collection.

You can edit the emission surface or volume at will, as well the delete volume. 

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Parameters:

On / Off: Enables the tree

Plane/Volume_Geometry: the chosen object to scatter instances. 

Density: Distribution value of instances, density is relative to the surface so if you raise or shrink it, the number of instances will follow.

Seed: Change all random values in the tree, usefull to test different random states since the seed remains.

Min_Scale: Minimum size of instances

Max_Scale: Maximum size of instances

Magnitude: Global scale factor

Scatter: ratio of scattered instances, 0 is none, 1 is full scattering. This function was first to scatter in volume since this feature was not available until recently. 

Distance: length of scattering

Delete_by_Volume: enable deletion of instances inside an object. 

Object: the chosen delete object.

Camera_Culling: enable deleting instances outside the field of vision. 

Picture_Ratio: 1920*1080 is 1.77, adjust it to your resolution for a better camera culling. 

Frame_Scale: use it to expend the culling to avoid border pops. (default value is 10) 

Focal_Lentgh: from the camera (driven here)

Camera: the chosen camera

Collection: the chosen instances collection

Material: material assigned to all instances

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Features:

One set of rock instances: About 20 small and medium rocks and three big ones. They all come with UVs but not very good, and a procedural shader with a bump. 

One set of debris instances: no UVs for those objects. 

A Fog Box: to add a volume shader to your scene. 

Improvements to do:

A lot! a probability node by instance number. 

fix culling behind the camera

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License: for any use, personal, educational or commercial.  

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By Sébastien Garnier, March 2023

Contact, feedback, requests: Anabase.studio@gmail.com