Emitter Material Questions

Announcements, requests and support regarding the 3DS MAX exporter
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ArielLyn43
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Joined: Fri Aug 26, 2016 1:43 pm

Emitter Material Questions

Post by ArielLyn43 » Fri Aug 26, 2016 2:23 pm

I’m conducting research for a Master project using Indigo plugin for 3ds Max. Specifically I’m trying to recreate primitive lighting in a virtual environment to see how it was used and affected our daily lives in the past. As you can imagine my lighting needs to behave as natural / general as possible with no or little creative tweaks.

I’ve studied Indigo’s manuals but still have questions in connection with emitting materials that are preventing me from moving forward on my project. The bigger picture is my colors are too dark but before I can address that issue I need to know my base settings are correct. Any questions / issues you can help answer would be appreciated.

System Details: Indigo build 3.8.831, 3ds Max 2015

Questions:

1) Indigo materials in Max have two emission node connection points, both labeled emission map, is one linked specifically to base emission?

2) What is the best / correct way to input emission RGB values in Max’s Indigo materials?

That probably sounds rudimentary but there is the Spectrum node, which has the gamma control option, and direct input to base emission in the material. I’m assuming the Spectrum node overrides the base emission but just want to check that both are computationally correct options. I should add I’m using linear Adobe RGB data and viewing on a Full gamut Abode monitor.

3) What is the best / correct method to input tabulated emission data into Indigo materials / nodes in 3ds Max?

The only way I’ve found is to create an Indigo material (igm file) and link it to the Indigo external node in Max, but this method does not appear to offer any means of Intensity control in Max. It also seems that the igm file is not capable of storing the intensity data as intensity in Indigo standalone appears to be attached to objects on a higher level.

4) I need to know the unit of measure for Intensity in Max’s Indigo materials and its relationship to the exponent value.

Known intensity is critical to accurately reproduce my lighting; is it flux, cd, lumen, etcetera? How is the exponent value affecting the intensity unit (like 100 lm to the power of 25) or what is the quality or formula the exponent is acting on.

5) Is there any potential conflicts between the intensity unit / exponent in Max’s Indigo material UI and values entered in the Indigo standalone Object UI.

My concern here is that the Indigo Max values, like the exponent, may affect the standalone values should I decide to export to the standalone and select a different intensity unit or change the values.

6) What are the recommended gamma settings in Max when working with Indigo plugin?

Right now I have the gamma correction set to auto 2.2 and have checked both “Affect Color Selectors” and “Affect Material Editor”. The only other option is to deselect auto.

Thanks in advance for your help.

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Jay-ko
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Re: Emitter Material Questions

Post by Jay-ko » Fri Aug 26, 2016 9:12 pm

Hello,
Find here my 2cents if that could help you....
First, know that the "manual" is not user friendly and lot of recent update are not into it.
Then, the 3ds max exporter is almost not usable to experiment the true power of indigo.
Also you have to be very carefull because the interface of indigo doesn't show everything.

It means that, as a 3ds max user, you have to tweak a lot the xml/igs code to be able to do the same stuff that a Cinema4D user or a Skecthup user.

- base emission is base, emission map is a filter of the base
- RGB values in a spectral renderer is a bit strange for me. use emission base with an higher value than 255 (it is possible to increase the "luminous power" of a color)
- Good question about the color spaces and the gamme used, in my workflow I stay linear.
- it is possible to link an external file into 3ds Max but the link doesn't work well, sometime it give error (like pink color) you have to check/correct the igs on a text editor
- the intensity is linked to the <model2>, it is "material agnostic"
- Excelent question--> Nick if you can answer exactly !
I always check the igs, to know more about that, and double check in the Indigo interface, it seems be lumens...
- Because of the lack of functionality the exporter, I do not use 3ds max to setup "correctly" an intensity
- for my side, I use the automatic 2.2, all the igs exported are "no-linked" to the 3dsmax file


And yes my best friend is notepad++ since I use Indigo :D
errare humanum est

ArielLyn43
Posts: 11
Joined: Fri Aug 26, 2016 1:43 pm

Re: Emitter Material Questions

Post by ArielLyn43 » Tue Aug 30, 2016 1:02 pm

Many thanks for your advice. It looks like I will need to use the standalone Indigo to handle lighting / emitter materials. Doing so will eliminate many of my concerns.

I appreciate the tip in regard to the system’s ability to accept RGB values higher than 255. I’ve tested several different tabulated data / wavelength conversion methods and some XYZ coordinates were returning RGB values higher than 255.

As I touched on briefly in the first post, I am experiencing emission colors that appear darker than they should be. I have a small real world stage (roughly 1.5 m wide x 1 m tall painted Munsell N8) and an identical virtual stage to scale so I can make lighting comparisons side by side. As an initial test, I collected wavelength data from a 150 watt studio lamp and applied it to a disc the size of the lamp reflector. The real and virtual lamps were place in the same position relevant to the stages. The real light is around 3000k so it makes a yellow cast on my grey stage, but my data has been generating a surface color closer to golden honey. Also if I move my virtual emitter 20 cm away from my stage the color seems to darken / attenuate way to fast; in real life the light 3 m away would be dimmer but still retain a saturated white yellowish look.

My first thought was it might be gamma. To try to eliminate any gamma problems between Max and Indigo, I tried the emission data (both in wavelength and RGB form) in the standalone Indigo but got the same honey color results. The emission color seems to be too desaturated (in the additive color sense), like it needs to be closer to the white point. I’ve tinkered with the linear tone map scale, camera settings, intensity, and gamma through max’s spectrum node. The closest I have come to a match is tweaking the gamma to about .2 using the spectrum node and RGB data.

Any thoughts on what might be causing the simulated halogen lamp light to appear honey color / desaturated?

Here’s some more relevant data:

>I have a twin monitor setup on a Quadro 4000 - 1 sRGB and 1 full gamut Adobe 1998 (main)
>My RGB colors are linear Adobe when used
>The virtual stage material is an Oren-Nayar with no images used for textures.
>I have tried both camera and linear tone mapping
>Emission / color data was collected by me using a spectrometer (direct and from a diffuse target yielded the same results)

Side Note: I should also mention Max’s photometric lights also appear to render darker then what I would expect for my environment.

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Jay-ko
Posts: 137
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Location: Paris

Re: Emitter Material Questions

Post by Jay-ko » Wed Aug 31, 2016 9:20 pm

You should do not use camera tone mapping except if you have your proper real camera profile.

keep it linear.

And then, how many lumens or lux send your 150 watt studio lamp?
Perhaps you have to calculate the "real" surface of your emitter to be able to attribute a corresponding value regarding the surface area.

Check the "real" size of the exported scene, sometime when 3ds max is not correctly setup the result export is something not in meter. (you should have this infos in the indigo interface)

Apply a correct white point with a material reference of a "true" real white.
errare humanum est

ArielLyn43
Posts: 11
Joined: Fri Aug 26, 2016 1:43 pm

Re: Emitter Material Questions

Post by ArielLyn43 » Sat Sep 10, 2016 4:18 pm

Thanks again Jay-Ko.

Sorry for being so long replying to your post. I've been studying the system and I'm starting to get a handle on how it operates.

> I switched to linear and that appears to be an improvement.
> In regard to the studio lamp intensity, I collected the studio lamp data as just an initial test of the system. I was hoping the XYZ data/ tabulated data would provide the luminance from the Y value. In reality the intensity drops as the spectrometer moves further from the sample. I collected the color data but didn't take the time to place the spectrometer at the proper distance to calculate true Candela, Lux, etc. Not a major concern right now but my best guess is around 750 Lm.
> My environment is real world scale in cm but I'm going to double check it in Indigo.
> My white point is set to D65.

One of the tricks I've figured out: When you use the spectrum node in Max it override the base emission intensity inputs. Because of this Max has no light intensity values resulting in a black render, but if you export and select emission type/value in the Object roll-out it fills in the missing data and renders just fine.

I'm going to spend the next few days studying the system in more detail. I'll post again in the near future with my findings.

Cheers.

ArielLyn43
Posts: 11
Joined: Fri Aug 26, 2016 1:43 pm

Re: Emitter Material Questions

Post by ArielLyn43 » Mon Sep 26, 2016 4:24 pm

You called it right Jay-ko:

My scale was off resulting in the perception of incorrect attenuation and luminous values. I usually work in Maya with only one scale value and didn’t realize the measure scale was separate from system scale in Max. I have the scene set to meters now and the attenuation is functioning as it should.

The white point (WP) appears to be my final issue and I could use a little more advice.

When I first set up my scene I set my white point to D65. My logic was Adobe 98 and sRGB use D65 WP’s so I should use RGB colors referenced to D65. After realizing the white point is linked to the camera settings in Max, I’m now thinking the WP setting is just simulating camera tone balancing without regard to color space.

I started playing with the WP settings to see the effects on my render. D65 was a honey color, ”E” was better but still too warm, but “A” seemed to be accurately simulating my Munsell N8 stage with a slight orange / tungsten tint.

I also tried the “Pick white point” tool which was easy to use because my virtual stage also has three simulated color references: an X-rite card, QPcard, and a Spyder cube. It gave me WP coordinates close to the “A” WP but seems to lack the tungsten tint I observed on my real stage.

Questions:

- It appears my white point needs to be set in relation to my emitter type, in other words my tabulated halogen / tungsten lamp produces colors expected under illuminate “A”. Is this true?

- Is the WP picker a reliable tool to set WP in your opinion?

- Am I right in thinking Indigo calculates color without regard to any color space?

- What color space does Indigo use when saving renders to image files like PNG?

- I also found that the colors of my saved PNG images are slightly cooler then what I see in the indigo standalone view port on both of my monitors (sRGB and Adobe 98). This is actually good as my PNG images are closer to what I expected. Just wondering if this is normal for Indigo?

Side note: I stated a low lumen output on the test lamp in my last post, it’s probably closer to 2500.


Many Thanks In Advance

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Jay-ko
Posts: 137
Joined: Mon Nov 12, 2012 7:28 pm
Location: Paris

Re: Emitter Material Questions

Post by Jay-ko » Tue Jul 18, 2017 11:10 pm

Hello,

Sorry I didn't see your message here, these questions are still open?
errare humanum est

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