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Create a Copy to Points SOP and wire geometry to be instanced into the first input, and positions to instance to in the second input. 

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Instance OBJ

Create an Instance OBJ as you would normally create Houdini instances. 

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In the Instance node, set your Instance object and select Fast point instancing or Full point instancing. Currently these two options result in the same behavior in the renderer.

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To override material for the instanced objects, we can use the Material SOP inside the Instance.