Currently, every exported Revit element gets a corresponding glTF node. For most elements, this makes sense. For example, each exported column should each have one glTF node.
This makes less sense with more complex elements--in particular the ones with nested instances. Here's a railing from the Snowdon data:
Currently, this exports as a single glTF node with one mesh and one mesh primitive. However, there's obvious instancing going on in the balusters.
Here is Revit's event order for the above element:
OnElementBegin
OnInstanceBegin
OnInstanceBegin
OnPolymesh
OnPolymesh
...
OnInstanceEnd
OnInstanceBegin
OnPolymesh
OnPolymesh
...
OnInstanceEnd
OnInstanceBegin
OnPolymesh
OnPolymesh
...
OnInstanceEnd
...
OnInstanceEnd
OnElementEnd
Each inner OnInstanceBegin....OnInstanceEnd sequence corresponds to a baluster.
We could makes these nested instances their own glTF nodes. The advantages would be that a hash-based instance detector would certainly detect these as GPU instances. It's also highly likely they could be instanced in Revit to reduce export time, file size, etc.
Here are elements in the Railing category of Snowdon isolated. The above element along with two similar ones are in blue:
Since balusters often have curved surfaces, these inner instances could likely account for a large number of repeated high-poly meshes.
The above railing is one specific example. Inner instances appear in more than just railings.
Currently, every exported Revit element gets a corresponding glTF node. For most elements, this makes sense. For example, each exported column should each have one glTF node.
This makes less sense with more complex elements--in particular the ones with nested instances. Here's a railing from the Snowdon data:
Currently, this exports as a single glTF node with one mesh and one mesh primitive. However, there's obvious instancing going on in the balusters.
Here is Revit's event order for the above element:
Each inner
OnInstanceBegin....OnInstanceEndsequence corresponds to a baluster.We could makes these nested instances their own glTF nodes. The advantages would be that a hash-based instance detector would certainly detect these as GPU instances. It's also highly likely they could be instanced in Revit to reduce export time, file size, etc.
Here are elements in the Railing category of Snowdon isolated. The above element along with two similar ones are in blue:
Since balusters often have curved surfaces, these inner instances could likely account for a large number of repeated high-poly meshes.
The above railing is one specific example. Inner instances appear in more than just railings.