Optimizing Inventor Scenes

Here are a few heuristics I have worked out over the last 6 months playing with inventor in the cave.

Some useful tools:
ivview - to view an inventor object
ivquicken - to speed up an inventor object. ivquicken produces a binary inventor file so you will also need ivcat to convert it back to a readable ASCII version
gview - to view an inventor object and its scene hierarchy and dynamically modify both. It crashes a lot but is VERY handy
showcase - gives you an easy (???) way to generate simple inventor shapes, and more importantly can write out inventor format. So showcase can be a nice conversion tool.
One of the main goals in optimizing inventor scenes is to reduce the number of nodes in the scene hierarchy, specifically those nodes that are not drawing polygons. As people tend to create inventor files from other applications, rather than by hand, the converters into inventor tend to do a very bad job of optimizing the inventor scene hierarchy. Here is a list of things you can do to help speed up your hierarchy:

• remove label nodes. Converters tend to add these in all over the place and they aren't very useful. You can always 'tag' a node instead of using a label so generally all these nodes can go
• consolidate materials. converters tend to put a new material node into every part. If possible try and add the materials once and then all the nodes that use that same material, then go on to the next.
• replace soseparator nodes with sogroup nodes wherever possible to avoid pushing and popping the current state.
• leave the render caches and the render culling alone. I haven't been able to outguess inventor in setting these.
• consolidate and improve shape hints. converters tend to put in a lot of shape hints nodes that do very litle. If possible try and consolidate these into a few well chosen shape hints nodes, preferably one at the top.
• improve shape hints. converters tend to provide very bad shape hints nodes because they do not provide good vertex sets or normals. This means inventor is forced to leave back sided lighting on and is not culling back faces so if possible try and put:

      ShapeHints {
          vertexOrdering COUNTERCLOCKWISE
  	facetype CONVEX
          shapeType SOLID
          }
  

  
  at the top.
• avoid rebinding normals. converters tend to put one normal binding in each subshape duplicating a lot of effort. Try and put a single normal binding at the top of the file.
• ivquicken is always a good last step though once a file has been ivquickened it may not be as easy to modify so I would keep a non quickened version as well for future work.
• I have on ocasion had to reorder the vertices and reassign the normals from a converter since either the original package didn't do it right, or the converter didn't care. This is not fun.
• ivperf can give a pretty good general idea how fast the object is and whether a modification helped much. Be sure to run it several times, especially in EVL since people are always logged into every other machine in sight.
• all of these pretty much have to be done by hand which is unfortunate. gview is very nice for finding parts of a scene graph that do not contribute to the actual scene so click on everything. This is especially true if your file came through a CAD package which is going to put all kinds of microscopic text into the file.
• that's what I can think of off the top of my head. If I think of any other important things I'll let you know, and if you think of any please let me know.