units

[Da_elf]

ok ive never really gotten my head around this. i opperate mainly at system units where 1 unit = 1 cm and usually work in feet with decimal inches. sometimes i put display units in cm. now ive got a problem where i was trying someones settings for juice and mine just did not come out like juice at all. what affect does system units have on 3S?

[3DMK]

System units is very important for most things in Max & Vray & I would advise making sure ALL your scenes have real-world sizes.


It is possible that the juice settings worked fine in the previous persons scene & NOT in yours due to a difference in scene scale. They may have used 1 unit = Meters & yours as you stated is 1 unit = cm's.
If any of the juice material settings rely on unit size , such as SSS then it would NOT work the same in scenes with different scales.

Hope this helps

[leehumphries]

For many years ive been in a similar situation regarding units...I work in metric and always had Display Units - Metres and System Units Millimetres..
I found many problems with this when it came to following tutorials for realflow and rayfire..Recently i tried using a tutorial for 3ds max Cloth mod and could never get it working correctly.

I came to this conclusion,ignore Display Units and keep it on Generic Units and change the System Units to metric ie.millimetres etc.....Now all the tutorials i seem to test work fine.

Maybe someone could expand on this

[PIXELBOX_SRO]

i always use system and display units the same....works best for me

[3DMK]

Maybe someone could expand on this

--System units are what everything in max & vray are really using & is what you really need to worry about

--Display units are just a way to make using max easier for input of numbers [& at times more confusing...lol]
Display units are converted back to & stored as system units within max

Hope this helps

[Da_elf]

right. what im saying is i know the system units are important. but what id really like to know is what system units does vray really want

[dellis]

Just as a little reminder you can type in whatever units you want and MAX will convert them....as long as you use the correct unit description. So if your system unit is meters and display is inches, and you need to make something 24 inches, you can type 2' or 60.96cm or 609.6mm or whatever. Hope that's useful. Oh and i think VRay wants meters if i remember reading correctly a while back.

[Donald2B]

I have 1 unit = 1 inch and VRay works just fine. I have never really had any problems. The major problems I have had lately involved scenes from another company that were setup as 1 unit = 1 foot. That created all kinds of issues between the two different files and things like that.

[3DMK]

right. what im saying is i know the system units are important. but what id really like to know is what system units does vray really want

Vray dosn't care what units you use....BUT if you use a unit scale that makes alll your object co-ordinates really massive numbers you will get ray-trace errors. It's all about choosing a system unit that best fit's the size of your scene

EG: Don't use cm or mm in your system units if the bounding box of your scene is a 5km.

Cheers

Cheers

[plastic_]

The fog parameter in the Vray material is a problem.

It doesn't operate with world units, so there is no conversion if you switch system units.
Personally I use 1cm as system unit, and display unit too.

It depends on your scene scale, for really big scenes it would be better to use a larger unit, or vertex positions will be corrupted if things are too far away from the origin.

[jujubee]

I understand one is for display (typing in numbers) and the other is the actual working space.

However I did hear some people encountered various decimal precision issues when working in Feet and inches (US Standard) and making conversions back down to Meters, etc.

I pretty much want to work in Feet and Inches because that's most of the files I receive here in the US. (Trust me, I'd just love if everyone here made the conversion over to the Metric system but that's not happening this century.)

I also had issues with light multipliers (IES, Wattage (although this is really arbitrary), etc.) having to be boosted tremendously in the past which I think is somehow related to system units.

So my question is - what is the best practice for actual system units that you're working in while keeping display Feet and Inches if you're in the US? Also, there's other "issues" that can be encountered going between programs such as Sketchup.

On paper, you would think it shouldn't matter as Vray would automatically make the calculations between various system scales. Plastic above pointed out an example above that has fog parameter issues. I've encountered that as well and had some problems following various tutorials on the web.