Exporting Blender 2.8 tangent to ogre XML

[mrmclovin]

Doing an experimental blender 2.8 exporter for ogre2.

As far as I understand, a Blender vertex can have multple tangents depending on which face the vertex participates in. In Ogre2's mesh XML, I can only specify one tangent per vertex. Does this mean I cannot map Blender's tangents directly to Ogre?

[dark_sylinc]

Hi!

When a vertex has more than one normal or tangent, the only solution is to duplicate the vertex. That's how traditional GPUs work.

Cheers

[mrmclovin]

Hi!

When a vertex has more than one normal or tangent, the only solution is to duplicate the vertex. That's how traditional GPUs work.

Cheers

Thanks for the article. That cleared up things I haven't thought about. Just out of curiosity regarding the optimizations, e.g. a 36 vertices cube with some vertices that share the same normal, and hence one can be eliminated - isn't this type of non-destructive optimization something that should be done in Ogre's XML importer? It would definitely make it easier to make exporters, as you wouldn't have to implement the same advanced optimization algorithm for each exporter. Instead it would be the quick and dirty way without loosing performance

[dark_sylinc]

Just out of curiosity regarding the optimizations, e.g. a 36 vertices cube with some vertices that share the same normal, and hence one can be eliminated - isn't this type of non-destructive optimization something that should be done in Ogre's XML importer? It would definitely make it easier to make exporters, as you wouldn't have to implement the same advanced optimization algorithm for each exporter. Instead it would be the quick and dirty way without loosing performance

Importers are usually in a better position since they can detect duplicates as they add new vertices to their sets, and dump only what's necessary (producing smaller outputs and thus improving performance)

Blender is an exception though since an exporter written in Python has poor performance.

Exporter performance is also often second class citizen, since it happens offline. Iteration time is still very important though (i.e. modify -> view in-engine -> modify) but you can script two paths: unoptimized (doesn't remove duplicates) and optimized (removes dupes).

• MeshMagick supports removing duplicates. You have to convert it to v1 first though.
• DERGO also has VertexUtils::shrinkVertexBuffer but it's more basic: It removes binary-exact duplicate vertices, and it's just code. It's not an offline tool.