Meters, Decimeters, Centimeters

[Ashley]

Hi,

I want to clarify a few things about TG units.

1.Does TG default to meters?

2. I know there is an option to load obj in cm, but I've read a thread here that mentioned a bug which causes this function to actually load in decimeters?

3.For my purposes, decimeters is my preferred scale to work at.
Is it currently possible to load obj, and/or set the world units to decimeters?

Cheers 

[Hetzen]

TG works in meters. Just scale the object when you import. Do a test cube to make sure you get the ratio right between apps.

[Ashley]

I know the settings are in meters, but I'm after specifics regarding the conversions between these scales.
:-)

EDIT: Yep, I have a method for keeping things accurate, but every now and then TG treats scale and world co-ordinates a little different than expected.

Sure its within "acceptable" margins and I can tweak things into place but as I'm starting to deal with larger amounts of data and need to be consistent I'm trying to get all the facts before I right it off.

:-)

[Matt]

Hi,

I want to clarify a few things about TG units.

1.Does TG default to meters?

Yes.

2. I know there is an option to load obj in cm, but I've read a thread here that mentioned a bug which causes this function to actually load in decimeters?

Yes. So if you enable this on your object, it will scale it by 0.1 (the conversion from decimetres to metres).

3.For my purposes, decimeters is my preferred scale to work at.
Is it currently possible to load obj, and/or set the world units to decimeters?

With OBJs it should be simple. As long as your DCC app doesn't do any scaling on export and your units are decimetres, you can use the aforementioned feature on all your objects to read them into Terragen as decimetres.

When importing/exporting camera data, it is more likely to depends on factors which vary and are hard to set standard rules for. It gets confusing because an FBX file knows what units it represents (which seems like a good idea but it adds yet another factor for the reader/writer to consider when moving between apps). Each file can be different, but different tools and pipelines do different things with this data. So really the best thing to do is experiment with different powers of 10 for the scale until you get what you want. The FBX import settings should allow you to do this. The first numbers to try are 0.1, 1 and 10. If you have to use "weird" numbers where things are nearly right but not exactly correct, then there's probably something else going on which is not cause by scale. Unless the FBX pipeline got non-metric units mixed in somewhere.

[Matt]

Btw, "units hell" is the main reason why I've decided not to allow the units to be changed in a Terragen project. Consistency is important, and reliance on metadata to understand the data adds potential for mistakes to be made. A distance or position in Terragen can always be known to be a distance or position in metres, as long as the thing being talked about isn't scaled. This means we can build assets that have real-world scales that should be transferable to many different projects, other issues notwithstanding. I realise this often doesn't work out this perfectly in real life, with trees and such being shared that have strange scales, but at least there is a baseline which can be defined as "correct". Sometimes scenes do need to be cheated so that you know you're not working in metres anymore, but at least you can do this knowingly and it's less likely to affect other projects in the Terragen ecosystem.

That's my goal, anyway

[Ashley]

Great thnx for clarifying all that Matt,

I like that TG is reliable with m units.
Yes I have found with fbx cameras scaling by power of 10 seems to work.

I have found between especially Maya and TG that world co-ordinates need to be tweaked. Its as if the X or Z need to be flipped in TG for obj.
Although this can be tweaked by eye when lining heightfields up. I find trying to line multiple heightfields from Zbrush it gets messy and its usually best to keep it all as one terrain.

Cheers
Ash

[Matt]

Yeah, Z sometimes needs to be flipped between different apps.