Speedtree texture and collision tips

[morcroft]

I've made a few discoveries about Speedtree use in Oblivion: the limitations and a few workarounds. First, the only readily available Speedtree editor is SpeedTreeCAD (Lite) 3.4. There are a few differences between the trees this can produce and what Oblivion supports

Oblivion doesn't support fronds. It also doesn't support any of the fancy stuff in later versions of SpeedTreeCAD - so you don't need any version later than 3.4. Locating that is left as an exercise for the reader - but it's out there.

SpeedTreeCAD (Lite) doesn't enable collision editing or composite textures.

Fronds we can live without, but composite textures are what makes in-game speedtrees look so good, and you do look a bit daft if your character suddenly disappears inside a tree-trunk. So this note is mainly about the workarounds.

The biggest single thing is to start from a game tree. This will allow you to re-use the collision and also to kludge the composite leaf texture. So pick a tree with the right general characteristics for the one you want. The vanilla tree collisions are all just bubbled around the base of the trunk, but the shapes and sizes vary. Switch collision geometry on in the CS (f4) and find a tree you like. I've yet to understand the seasonal trees - those that finish SU, FA, and WI - I think the game may automagically switch between these through the year but I haven't looked into that.

I want a pretty big tree, with a nice fat base, and the common three-texture composite map, so I'm going to start from TreeBlackLocust. I'm making a Jungle tree for Black Marsh, so I'll create a folder called BmMdTreeJungle01 into which I'll put a copy of treeblacklocust.spt, and rename it to BmMdTreeTropical01.spt.

When starting from scratch, also put in a copy of treeblacklocustleaves.dds, edit it in gimp and extract each of the three texture sections to .tga files. These three files are the key to getting a composite texture map to work. SpeedTreeCAD never looks at the real composite texture - it looks at these three files, so you need to know what they're called - and it won't tell you: it'll just display the missing textures warnings and prompt for the filename. And if you change the filename, it breaks the embedded composite map.

But the real names of the files are written in the .spt file in clear text: so you can work it out! Using whatever editor you like, search the .spt file for .tga files. Don't change anything, just note down the texture files. SpeedTreeCAD also ignores any file paths, so you just need the names. For the Black locust there are four textures:
TreeBlackLocustLeaves01.tga
TreeBlackLocustLeaves01.tga
TreeBlackLocustLeaves01a.tga
TreeBlackLocustLeaves01b.tga

And yes - two of them are the same. Rename your three texture files to match. You'll probably need to play around, but I think TreeBlackLocustLeaves01.tga is the big one at the bottom, and the other two can be either way round.

You should now be able to open the .spt file. You then just need to morph the model to suit the tree you're actually making.