importer/exporter units

[colin]

hey guys - first post...

i was wondering about the import/export dialogues native size/scale parameters.
in the c4d EXPORTER it lets me set my native unit size. so if i, let's say, work in centimeters within c4d i choose cm as my native unit size. now...
in the octane IMPORTER (i.e. obj mesh import preferences) it lets me choose which units of my imported obj files get transformed into meters. so if i. let's say the units of my modeling software are cm i choose centimeters - to meters.

i'm now slightly confused of me telling the system my modeling apps units TWICE.
if i tell the c4d exporter that i work in cm, does it transform those units into meters when generating the obj file. if that's the case - should i choose "meters to meters" in the obj-file units drop-down, of the octane importer?

hope that makes sense...
colin

[abstrax]

Hi Colin.

The C4D exporter always converts to meters, which is the default unit of Octane (also used internally). For example, if your native unit is centimeter in C4D then every coordinate gets divided by 100 during the export, i.e. 100units in C4D will be 1unit in Octane.

I think, Octane also allows you set an import, if your exported OBJ file is not in meters. If you use the C4D exporter, you don't have to worry about it and should just stick with the default unit in meters.

Cheers,
Marcus

[colin]

thanx abstrax,

just as i suspected...
so - is there a way to CHECK if my scene units are wrong?
let's assume that sooner or later i'll import an obj i didn't do myself. how would i go about checking the scene units used?

just out of curiosity, if those units ARE imported wrongly - would octane simply not work, work buggy, or would just the navigation become harder?

thanx again,
colin

[colin]

i guess that's a no then

[abstrax]

thanx abstrax,

just as i suspected...
so - is there a way to CHECK if my scene units are wrong?
let's assume that sooner or later i'll import an obj i didn't do myself. how would i go about checking the scene units used?

just out of curiosity, if those units ARE imported wrongly - would octane simply not work, work buggy, or would just the navigation become harder?

thanx again,
colin

Sorry for the late answer.
OBJ files don't contain units. Octane works ok as long as the numbers are in a reasonable range. I have seen artifacts if objects are too small or too large. In the end you will have to try out and if the scene scale is not correct, you will have to change the export settings. I don't know of any other way to determine the export scale after the export.

Cheers,
Marcus

[acc24ex]

Hi Colin.

The C4D exporter always converts to meters, which is the default unit of Octane (also used internally). For example, if your native unit is centimeter in C4D then every coordinate gets divided by 100 during the export, i.e. 100units in C4D will be 1unit in Octane.

I think, Octane also allows you set an import, if your exported OBJ file is not in meters. If you use the C4D exporter, you don't have to worry about it and should just stick with the default unit in meters.

Cheers,
Marcus

Ok, that's a bit confusing, can you suggest which units to use in order to be on the safe side..
By reading this, it is OK to assume to use cm units by default (that's what I use) Octane will translate 100cm to 1 meter?
I know that you get artefacts with a too large a value - circles on polygons.. don't really know how a smaller than scale looks.. so if someone has the time to test a box with a too large of scale and a too small one so to test how it looks assuming you know exactly what the units are?

The plugin automatically starts the render as well so we can't really change the scale before it starts doing its magic - not that I complain I like it that way - it loads it faster than those other external renderers (a 64 bit system and 16xPCIX slot probably helps )

[abstrax]

Ok, that's a bit confusing, can you suggest which units to use in order to be on the safe side..
By reading this, it is OK to assume to use cm units by default (that's what I use) Octane will translate 100cm to 1 meter?
I know that you get artefacts with a too large a value - circles on polygons.. don't really know how a smaller than scale looks.. so if someone has the time to test a box with a too large of scale and a too small one so to test how it looks assuming you know exactly what the units are?

The plugin automatically starts the render as well so we can't really change the scale before it starts doing its magic - not that I complain I like it that way - it loads it faster than those other external renderers (a 64 bit system and 16xPCIX slot probably helps )

Missed that response, too. To make it short: Usually you should always choose the native unit that you were using when you modeled your scene and forget about the rest.

Octane is physically based and because of that it needs to store its data with some unit. The coordinate system in Octane is based on metres and by default imported geometry is not scaled. That means if a cube in the OBJ file has width of 1.2, Octane interprets that as 1.2m. To make sure that the exported geometry has the correct scale, you have to specify the native unit in the export dialog. If you for example modeled in cm, your cube would have width 120. By choosing a native unit of cm, those 120 (cm) get translated to 1.2 (m) during the export.

Don't worry about any import units in Octane - this might only become important, if the OBJ file has not been exported using the Octane exporter.

Cheers,
Marcus