Accurate Lighting for a court case

[3ply]

I'm trying to accurately show the lighting conditions in a space. I'm currently using 3dstudio max Mental Ray and the lighting analysis feature. I have the building oriented properly and using the daylight system with the correct location date and time. I'm using architecture & design materials. The light levels feel way off. I'm getting roughly 1100 fc for an interior space with no artificial lighting. There is an over head door and several windows. All the openings are on the North side of the building. The rendering is very dark. How accurate is the lighting?

 

There seems to be a lot of settings I can change to manipulate the rendering such as exposure control.

 

Any help would be greatly appreciated.

[Scott Dombrowski]

Max can do lighting analysis with mental ray. I used it a while ago for the LEED 8.1 credit. 1100fc does sound quite high. There's a good tutorial about how to set it all up here:

 

http://help.autodesk.com/cloudhelp/2015/ENU/3DSMax-Tutorial/files/GUID-8E4DD78A-BA25-414C-AB1F-3E840C1FFA48.htm

 

As I recall, it's better to not use textures for lighting analysis. Instead, use a flat grey material with the appropriate Light Reflectance Value of each surface.

 

Autodesk wrote two white papers that go into more detail on the process, but they don't appear to be on the Autodesk website anymore. Go figure. If you do a Google search for "3ds_max_design_2009_daylight_simulation_getting_started.pdf" and "3ds_max_design_2009_daylight_simulation_advanced.pdf", you'll find them.

[harryhirsch]

''A picture is worth a thousand words'' Fred R. Barnard

[3ply]

Thanks for the quick response. The lighting levels for the autodesk rendering seem off. The center of the tennis court is roughly 2400 lux. Typical office lighting is about 500 lux. The tennis court seems rather dark. Am I reading this wrong?

 

I'll have to go through the tutorial to get a better understanding of the proper way to set my scene.

[John Dollus]

''A picture is worth a thousand words'' Fred R. Barnard

 

A picture is worthless as a defensible document in legal proceedings without the corresponding thousand words.

 

The exposure controls are visual only and will not affect the data but you should follow Scott's great advice about sticking with diffuse colors only and input the true reflectance values of the materials. You may want to back it up with 'real' lighting analysis software to verify.