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dvalenzona820934
2009-03-04, 03:10 AM
Hello All,

I have a question regarding the daylight simulation modeling of 3DSmax. Particularly the foot candle numbers for an interior space. I did a quick study of a library with daylight only. See attached image. I thought the appropriate range for foot candles in interior spaces were between 50 and 100. I'm getting numbers like 400...
I followed the directions in the white paper on daylight simulation modeling, but I'm not sure if there is a decimal point before the last number, i.e. 400 is really 40.0?
I confused can someone please illuminate me? (Pun intended...)

Thanks for any help,

Don

stusic
2009-03-04, 10:21 PM
I haven't run into that problem and your scene looks correct, so all I can suggest is to go back over the settings and make sure all are correct... Only a couple things I can think of to double-check:

Are you using the CIE Sky Model? If so, are you set to display Daylight Factor Values? If not, make sure you're set to display Total Illuminance, not just Direct or Indirect Illuminance -- this can get those numbers even though your scene is accurate.

I hope this helps; I've only done a few lighting simulations in my time.

dvalenzona820934
2009-03-06, 09:03 PM
Hi Phillip,

Thanks for the help.
I did check the illuminance level and I am using Total illuminance.
For the sky I'm using the gov.epw file (WDF).

I emailed Steve Bennett and asked for his advice, and maybe it will work.
He suggests changing the footcandle value range to the appropriate levels. I had them from 0-9600...
And adding daylight portals. The model was originally created in revit, and I'm afraid that I haven't researched the correct settings for portals and glass materials for rendering in 3dsMax. I'm going to try a few things and post up the results.

Thanks so much,

Don

stusic
2009-03-14, 06:06 AM
The model was originally created in revit, and I'm afraid that I haven't researched the correct settings for portals and glass materials for rendering in 3dsMax.

If you render the scene and it looks right, the glass/glazing/window/portal/material should be correct. If you think it may be that causing the problems, just hide the window's glass object and try it again. If the numbers are dramatically different, then you've found your problem; if they aren't, then the problem lies elsewhere. The numbers will be a little different because the light isn't going through anything, whereas with the window object shown, it is actually going through something.

ramyhanna
2009-05-06, 01:55 PM
Also remember what you see in the rendering isn't a factor of what the fc are, it's just a rendering with exposure adjusted to look right. Be sure you're using ProMaterial Glazing (it will attenuate light properly).

You can also check out my posting on Daylight Simulation (http://3dsmaxrendering.blogspot.com/2008/08/max-2009-lighting-analysis.html).

swalton240189
2009-07-09, 08:21 PM
I'm just starting out with daylighting in 3dmax myself but looking at the image you posted it looks like the image is set to haze instead of CIE that was giving me 400 fc results also.

I would also check your glass material. If you edit the glass color the "Value" field is the resultant visible light transmittance after passing through the number of polygons in the "Refraction Levels (N. Poly to Travers)" field. So if in Revit your glass is modeled as 2 layers, you should set that field to 2, otherwise it should be 1.

swalton240189
2009-07-10, 09:05 PM
I think I was mistaken each face of glass traveresed counts as a polygon so I think it should be set to 2 if you have one layer of glass; and 4 if you have 2 layers of glass.

(page 7 of the advanced white paper. http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=11360846 )

BDR_Architect
2010-01-26, 07:45 PM
I thought I read somewhere that the light meteres read most accurate with the Perez All Weather sky with the EnergyPlus weatherdata. Especially for LEED simulation. I see alot of people talk about using CIE sky on AUGI. I've even run some of my own tests and have come to the conclusion the Perez is the way to go. Am I mistaken?

What are your thoughts?

Steve_Bennett
2010-01-26, 08:42 PM
I thought I read somewhere that the light meteres read most accurate with the Perez All Weather sky with the EnergyPlus weatherdata. Especially for LEED simulation. I see alot of people talk about using CIE sky on AUGI. I've even run some of my own tests and have come to the conclusion the Perez is the way to go. Am I mistaken?

What are your thoughts?
I too was under the impression that the Perez All weather setting was required for running LEED simulations.

I have referenced these documents and found them rather insightful.
http://images.autodesk.com/adsk/files/3dsmax_started.pdf
http://images.autodesk.com/adsk/files/3ds_max_design-exposure_validation.pdf

swalton240189
2010-01-26, 08:57 PM
That's very serendipitous that this post has been resurrected as I'm doing my first LEED daylight study in 4 months.

I'm not sure which is proper for LEED.
It seems the PEREZ will use the cloud data from the EPW file. Since LEED 2009 wants a clear sky this may be a problem if the day you choose for running the analysis may be cloudy.

CIE may do the same thing I'm not sure?

stusic
2010-01-26, 11:14 PM
From my understanding (limited as it may be), CIE is best for scenes with no direct sunlight (overcast sky), while Perez all-weather is best for clear skies. I'm not terribly familiar with daylight simulations, but here is a source (http://greenbimnetwork.blogspot.com/2008/08/forum-daylighting-beyond-leed-part-1.html) that may help clear it up (or at least be more informative than I) - particularly number 3. It seems to be a lack in clarification by the USGBC in their requirements and SOP in daylight simulations.