Release: wom_archlight 1.0 - physically accurate light shader

#161

Interesting find guys. I admit I did not do much testing with using the same light shader on multiple objects, as I did most development/testing on SI (where this issue is unlikely to come up).

Anyhow, I am not at a PC where I can test, so I am hoping you can quickly try something to help track this down:

  1. Can you try turning off “Preserve Profile Shape with Area Lights” on the Advanced tab? It will make the light profiles fuzzy, but I am curious whether it otherwise solves your problem. If it does, I have a pretty good idea what I need to change to make a proper solution.

  2. If that does not work, can you try testing with the MI photometric shader to see if it has the same problem?

Thanks.

#162

Hi!

So I did your first test and it does seem to fix the problem, in fact even better than using multiple wom shaders, it removed a dark spot from the light profiles. I assume what I’m getting is the right result now!

#163

Thanks. With your tests I know exactly what is going on now. The missing dark spot is probably caused by the “fuzziness” of the light profile that I described. Basically, instead of a nice sharp light profile, the profile is being somewhat smeared across the area light. Anyhow, I will put a fix into the next version that should take care of the problem.

#164

Watch out I’m back for more! :wavey:

I’m using this shader a lot now so I’m mostly up to speed with it… but I have a couple of questions!

Is there a way to create a planar area light that only emits light out of one side? By default it seems to come from both sides which isn’t always easy to deal with. I think one way would be to create a custom IES profile, but I just thought I’d see what other people are doing.

Next question is, how does the photon intensity relate to the direct illumination intensity? I’ve created a test scene where I set up the same scenario in both Maya and Maxwell to see how the light levels compared (because I felt like the Wom intensity was really dark, but no, it’s fine). The direct illumination matched Maxwell but I had to crank the photon intensity on the Maya lightShape up to 50 million (leaving the Wom multiplier on 1) to get similar levels of bounce light. I can imagine with there being so many options on the shader it might be impossible to get the photon intensity to always match up, but if it turned out 50 million was a magic number I’d be very happy. :wink:

Wom shader on the left, Maxwell on the right. They both have a light set to 100 watts and an efficacy of 70. Same camera settings etc but yeah, had to set photon intensity to 50 million.

Last question comes directly from that image, the reflections are a little strange! The light doesn’t appear in the reflections despite being visible and there’s like a spotlight cone reflected in the chrome sphere?

I swear I’m not complaining I just want to be the Ultimate Wom Master!

#165

Hmmm…I thought the womArchLight was supposed to handle photon emission as well. Meaning if you plugged in an IES profile the profile would calculate the correct photon emissions based on the measurements from the real world light. But I guess in your test you did not plug in an IES profile…you were just using it like a regular maya light?

Or am I just totally off in left field here? :slight_smile:

#166

Jozvex: Did you connect wom_archlight as the photon shader as well as the light shader? When connected as the photon shader, the relationship between direct and indirect light should be automatically taken care of (ie, it should be correct when both the intensity multiplier and photon multiplier are 1). The photon intensity in Maya should actually get ignored.

Let me know if that solves the problem!

Also, to get the light to come out of only one side, there are actually two different approaches that can work. The easiest is to try turning on Cosine Distribution on the Advanced Tab. Note that using this has a few caveats: 1) obviously it will only work with plane or disc area lights, and 2) The total amount of light emitted from an IES profile won’t be fully correct anymore, as it will fade out at the sides.

Another potential idea is to try setting up an area spotlight, then set a 180 degree outer cone angle.

#167

Oh my goodness… you’re a wombat and I’m a dingbat!

I completely forgot about lights having that photon shader slot!! Thanks!

:blush:

#168

I love you wombat778. Thank you so much.

#169

Would anyone have any suggestions for creating a vehicles headlight. I cannot seem to find any ies files out there for cars either. any help would be cool.
A wom preset collection of assorted light types would be cool too… maybe an ies preview window. That would be awesome too. Not complaining. So happy we have this. Made me want a light meter in Maya.

#170

I’ve notice that on the mia_photometricLight in mentalray 3.8 release, the workflow is the same of your light, wombat. Great stuff.
Anyway, much control settings in your light :slight_smile:

#171

It would be nice to have this shader compiled for Maya 2011.
I think this shader works better than the native Maya 2011 one.
Also, with the wombat shader, you have the ability to emmit lights from objects, something that is still not present in mental ray for maya integration.

#172

Shadow threshold is the big one i’m use womlight. On mia_photometric is withou it and not productive.

Wombat we are in your hands

#173

Downloaded :smiley:
Thenk you so much vombat. :bowdown:
in one of these days I will do some tests.

#174

Thanks guys. I do plan to update it for Maya 2011 (and SI 2011), hopefully in the next few weeks.

#175

Cant wait! :bowdown:

#176

Hey there wombat,

I just fired up a quick render in maya 2011 with the latest shaders. I venture a guess you haven’t compiled them for 2011, but they kinda worked. Should I expect the same physical behavior as if the shader would have been compiled exclusively for 2011, x64?

#177

Hey Guys

Had a quick play with the new mia_photometric light shader in 2011 and im a bit puzzled...

 with an IES profile and wom light shader,light seems to behave correct,so if i convert that light to an area light the global intensity of it doesnt change,it only really affects the quality of shadows , but the scene keeps pretty much the same amount of lighting even if i go a bit crazy with the area size scale.So because the IES profile drives the distribution and  intensity this behaveour is to be expected .

   But its not the same  case with the mia_photometric,its actually very sensitive to light scale (note that im talking about light transform node scale no scene scale)to the point it acts as a intensity multiplier... so as an example if i set up my light as a spot, connect the mia_shader, add the profile and set it so  it drives the distribution and intesity (mode 2 for both) also I set the units to meter to 100 (im working in cm)if the light scale is 1 for all axis I got the same light as if i was using a wom archlight with the same IES profile,great!,

    but from the moment I change the scale of the spot light it affectsdramatically the whole intensity of the light, and this is unfortunate if you want to use it as an area light...
#178

Hi Miko,

That does not surprise me. When I was developing wom_archlight, I spent a lot of time trying to make it work so that changing from a point light to an area light would yield physically correct intensity (depending on the units selected). I have not tried mia_photometric, but it sounds to me like they didn’t make the same effort…

#179

Hey Wombat,

it would be great if you could add a cm2 value slot inside the RGB Unit Conversion so we can link it to the exposure photograpic shader like with the mia_photometric in 2011.

it will add a lot flexibility while working with plates and self illuminated shaders.

just my 2 cents.

#180

Hi Wombat.

Gotto say thanks first of all. I have installed on maya 2010 and it works wonderfully.

I then installed it on maya 2011. So it actually does work it seems even without a conversion from your side, but i get block artifacts (black block as if it didnt finish the render. those blocks are random every time.

Can you think of what will resolve it, or is it just the conversion to 2011 that will resolve it.

Again, you have created quite a stir amoung people like me. THANKS

Kind regards
Craig