system units effect on render time?

[martindrake81]

OK a quicky...

 

does it really matter which sytem units you use, eg millimetres over metres.

My real question is: does modelling a large scene in millimetres cause any issues with lighting calculations using standard, photometric or vray lighting?

[BrianKitts]

the units you use don't matter as long as you use them properly. You won't get proper results with photometric lighting if you don't model to scale, but that being said there is no hinderance on rendering time between having your units set between meters to millimeters or to feet as far as I've ever experienced.

[Brian Smith]

It doesn't affect render time just accuracy, although to an indiscernable amount unless your scene is a great distance away from the world origin. I actually just said as much in this post a minute ago.

 

http://www.cgarchitect.com/vb/21981-dimension-inaccuracies-max-9-a.html

[martindrake81]

Thanks for that guys

So I guess a good 'standard' is to model everything in mm unless you are modelling maybe a city?

[sterealkey]

Hi guys,

 

While we're on this whole system units mission here.

 

Could someone please help me configure mine properly, I'm posting a screenshot of what it is, which I thought is correct. But when making a 3ds export to use in other apps like sketch up, then everything is the wrong size, way too big or way too small , cant recall which exactly

 

Anyway, please look at my units setup and tell me if I have something wrong there.

 

Thanx in advance:D

[Ricardo Eloy]

Ok, there's a chance I'm saying something very wrong here, but...

I wouldn't change the System Units to mm. Max was made using inches as reference, so I guess it kind of expects everything to come in inches. What we do here (we work in centimeters) is to set the System Units to 1 unit = 0.025 meters, so we get rid of the 0.04 cm thing and have the model set right. At least it has worked for us so far, and we import and export thing a lot.

[Justin Hunt]

Remeamber ifyou do change the system units to mm and you bring in a maodel which was made with inches as system units, the scale is going to be totally out of wak.

 

This recently happened to me, I was doing the "Haunted Hallway" lighting challenge on CGTalk. That model is in inches (and very badly modeled at that). I then started a new project, but forgot to set the system units back to mm. All my CAD plans came in fine until I checked some measuments, they were 100000's out. I had to start from scratch with the correct system units. Waisted 2 days work

 

JHV