.3ds is an old format that comes from MS-DOS era, when 3ds Max was a program that ran in DOS mode. And yes it has its limitations. One of these is that it needs a correspondence 1:1 between texture vertices and mesh vertices,(texture vertices= coordinates in your bitmap texture, the one applied to your mesh)
It doesn't support multiple texture vertices for the same mesh vertex (a normal situation, that many actual formats fully support).
Think in a pyramid, as example for better understand the issue:
you will use only 5 vertices to build the mesh, but when you do the mapping, you will have 3 texture vertices per side and 4 for the base, 16 texture vertices as a result, so, all individual mesh vertices will be shared for several texture vertices (16:5). That is unsupported by 3ds format.
Probably you have seen that when you use 3dsMax to export a file to 3ds format, you will be faced with an option, checked by default: "preserve Max mapping coordinates", why is this?
because to resolve the anterior situation, and be able to convert the file to 3ds format, the program will add new vertices to your mesh in the places where several texture vertices are shared for the same mesh vertex, until the correspondence 1:1 between them is recovered.(16:16)
Now that the correspondence is restored the file can be saved. but is not the same exact mesh anymore, because where the new vertices were introduced the mesh has been splitted (two or more vertices are placed at the exact same point without being welded) and as side effect of this, the smoothing of original mesh has been broken.
In the other side, if you uncheck the "preserve Max mapping coordinates" what happens is that the mapping coordinates of your mesh are deleted, (you loose them), so they do not conflict with mesh vertices. The file is saved with smoothing groups intact but no mapping.
I think that Mesh converter uses first approach by default (without asking ) to not loose mapping coordinates. But I don't know how to change or fix this behaviour. I wish we have a dedicated tool or format with all features full supported to be able to import/export at any time without loosing any information in the process.
And, just in case you face similar situation, I made my models in 3dsMax 2009. But if I want to open them in 3dsMax9 to use Maraz exporter, I have to export them in .3ds format. (due to incompatibily with newer .Max formats between versions)
So, I use this workarround to overcome the situation:
-Add an "Unwrapp UVW Map modifier" to your whole mesh before export to 3ds, and from within the modifier, without changing nothing else, use the option "save UVW map" to save the mapping to some convenient place in your HD.
-Then export the file to .3ds format without preserving Mapping coordinates (unchecking the option before export, so no new vertices added, no smoothing lost)
-In 3dsMax9, reimport the 3ds file, add a new "Unwrapp UVW Map modifier" and use the option "load UVW map" .
-Now navigate to your UV's previously saved file and hopefully everything will be fine.
I hope is a bit clearer now, but maybe someone with a better understanding can explain it better, or correct me if I'm wrong.
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Topic: MshConverter 1.18 by Dr Jones ~ Link Updated (Read 48275 times)
