Portrait Light Package - What do these lights do?

Stryder87

I was working on a portrait scene using my usual light setup and thought, since I have a couple Portrait Light packages, why not try one?  So I loaded up DG Easy Portrait Lights, IBL 08.

The lights it put in are very different from what I'm used to using.  Can someone explain to me what a Specular Only and Diffuse Only light is compared to a regular light?  My guess is they only effect the Specular property and the Diffuse property of the surfaces, but what does that really mean?  There's an IBL light as well and I can't figure out what that thing does at all.  Ray tracing (I thought that was the number of times light will bounce between objects before it dissipates - affects reflections)... Occlusion... gah…

It does seem to make the portrait a little nicer though... 

mjc1016

Those sound like they are 3Delight lights.

In 3Delight you can separate the 'diffuse' and 'specular' components of  a light.  A specular only light will not provide and 'actual' light to a scene but will add the highlights and reflections that are what make up 'specularity'.

DestinysGarden

I'm glad they are making your portrait a little nicer...

MJC has the right of it. 3Delight spotlights have the ability to break out the part of the scene they illuminate. The Specular Only light shows highlights based on the specular value of the surface(s) in the scene, the Diffuse Only sort of goes the other way with it and shows the not specular parts, and Illumination On is for both. I did a proper botch up of explaining that, sorry. The main point for having the diffuse light and the specular light seperate is that it gives more control over the specular highlights, either higher or lower, than just the regular Illumination On function. The IBL light gives and overall color cast to the scene, fills in shadows and whatnot.

That particular light set was an attempt to recreate the sorts lights Daz was using for the generation 6 figure promos. It was a fun exercise.

Happy rendering!

Edit: I thought of somethng else, the bokeh background shader presets in that set were made to take advantage of the specular only lights too. I know one of them is greenish, but I put a contrasting red color in the specular channel, so that when the specular light hits it the color does that nice gradient thing fading from greenish to reddish.

Stryder87

DestinysGarden said:

I'm glad they are making your portrait a little nicer...

MJC has the right of it. 3Delight spotlights have the ability to break out the part of the scene they illuminate. The Specular Only light shows highlights based on the specular value of the surface(s) in the scene, the Diffuse Only sort of goes the other way with it and shows the not specular parts, and Illumination On is for both. I did a proper botch up of explaining that, sorry. The main point for having the diffuse light and the specular light seperate is that it gives more control over the specular highlights, either higher or lower, than just the regular Illumination On function. The IBL light gives and overall color cast to the scene, fills in shadows and whatnot.

That particular light set was an attempt to recreate the sorts lights Daz was using for the generation 6 figure promos. It was a fun exercise.

Happy rendering!

Edit: I thought of somethng else, the bokeh background shader presets in that set were made to take advantage of the specular only lights too. I know one of them is greenish, but I put a contrasting red color in the specular channel, so that when the specular light hits it the color does that nice gradient thing fading from greenish to reddish.

Ok, I think I'm getting a better idea... but... and this is so basic it's embarrassing… I still don’t really grasp what the Specular is (what effect it has in the scene (or the character skin I suppose)), and what the Diffuse is.  Mjc1016 said that a Specular Only light will “add the highlights and reflections that are what make up 'specularity'”.  I’d probably understand that better if I really understood what Specular and Diffuse was.

Also, what difference is there between the IBL light and a regular Spotlight with the colour adjusted?

The light set did make the portrait nicer… the skin seemed to look a little more real, but there were differences I wanted to adjust, but not really understanding what the lights did, I couldn’t figure out how to make the adjustments I wanted.  The placement of the lights had to be moved somewhat, which resulted in an overexposure area on the chest and lower neck, but I couldn’t seem to adjust it.

 

scorpio

Specular tends to make things more shiny or glossy, without it things look a bit flat.

Uberenvironment for example tends to suck out specular so a specular light only helps put it back

DestinysGarden

The easiest way to see what the IBL is doing is to do one render with it, and one withour it. It acts sort of like a dome in that it fills in the shadows and rounds off the figures in your scene. For the Specular only light, if you are getting blown out parts in your render, either turn down the intensity on the light, or turn down the specular value on the subject. I did a mini tut in this thread http://www.daz3d.com/forums/discussion/68274/how-to-make-layered-background-colors-in-daz-studio scroll down about midway, that shows very plainly the fun, not at all real world stuff, you can do with 3Delight. The specular light, in tandem with the figure's specular's setting is a way to hack the system. If the specular light only brings out highlights, the diffuse only light is almost the opposite in that it shows only the diffuse/base colors without highlights. For more fun with IBLs, change the image to any random image you have sitting on your hard drive and see how different the render looks. Really, the best way to gain experience is to make a change, push the render button, and see what happens.

Really good questions here Styder.

Stryder87

DestinysGarden said:

The easiest way to see what the IBL is doing is to do one render with it, and one withour it. It acts sort of like a dome in that it fills in the shadows and rounds off the figures in your scene. For the Specular only light, if you are getting blown out parts in your render, either turn down the intensity on the light, or turn down the specular value on the subject. I did a mini tut in this thread http://www.daz3d.com/forums/discussion/68274/how-to-make-layered-background-colors-in-daz-studio scroll down about midway, that shows very plainly the fun, not at all real world stuff, you can do with 3Delight. The specular light, in tandem with the figure's specular's setting is a way to hack the system. If the specular light only brings out highlights, the diffuse only light is almost the opposite in that it shows only the diffuse/base colors without highlights. For more fun with IBLs, change the image to any random image you have sitting on your hard drive and see how different the render looks. Really, the best way to gain experience is to make a change, push the render button, and see what happens.

Really good questions here Styder.

Those screenshots in your mini-tut are awesome examples and really help to understand the Specular and Diffuse lights.  Some question:

1- I'm going to guess that, in the examples in your tutorial, the Specular-only spotlight was behind the character, correct?

2- Just to be certain, the lights in the Portrait packs are UberEnvironment lights, correct?

3- If a normal spotlight only reflects the Diffuse colour, is there any purpose to the Specular colour channel of a surface using a normal spotlight?  Would you still use the Specular channel to adjust the glossiness when using a normal spotlight?  Does this work the same regardless if the spotlight is an Uber or AoA or the basic built-in one?

4- On the surface setting for my character in my portrait scene, the Specular(1) has the same colour as the Diffuse.  Diffuse strength is about 45%.  Spec(1) Glossiness is about 65%.  Spec(1) Noise Density is 20, Spec(1) Noise Strength is 0 and Spec(1) Strength is 0.  Spec(2) Colour is Black, Spec(2) Glossiness is about 95%, Spec(2) Strength is about 15%.  If the Spec(1) Strength is 0, but the Spec(2) Strength is 15%, how do those work together?  How do they work with the Diffuse?  How would a Spec-Only light work with the two different Spec channels when they are different colours?

5- Just what do those different channels actually mean (I think I understand the Glossiness one from what mjc and scorpio said)?

6- What's Occlusion???

Ok, I'll stop for now... 

Stryder87

Wait... one more question before I forget it....

Does a Specular (or Diffuse for that matter) light actually cast a shadow?  I see the settings are for 100% shadow, but don't really see one.

Ok, done for tonight. 

mjc1016

Yes, they cast shadows...but the 'softness' also comes into play as to how noticeable they are.

DestinysGarden

1-Yes. the specular light was behind the person sort of close to the backdrop.

2-The IBLs are UberEnviroment lights. The rest are standard spotlights and distant lights.

3-A regular spotlight set to Illumination "On" will illuminate both diffuse and specular. Change to "Diffuse Only" and you get no specular highlights. Change to "Specular Only" and all you get is specular highlights. Change to Illumination "Off" and you get no light.

So, if you are using a regular spotlight just set to be on, the only way to adjust any specular highlights is on the surface itself, or by adjusting the overall amount of light, which may make your scene too bright or too dark. If your light is specular only, you can adjust either the surface, or the specular only light, without changing the overall amount of light in the scene. The basic set up on this particular set of lights was a standard photography 3 point system Key, Fill, Accent. There is a Key light set to Illumination On (both diffuse and specular), which is the main directional light source, a Diffuse Only light to Fill in, or brighten up, shadowy parts of the scene with out adding highlights, and a Specular Only light to Accent certain highlights. Some of the set ups have an additional Fill Light, Accent Light or Rim Light. The UberEnvironment IBL provides general, coming from everywhere, ambient light. It is like the wrapper on the package, the thing that ties it all together and makes it cohesive.

Yes, the same principles apply no matter what type of light you use. I guess I get wordy in the morning. Apologies if that was long.

4 &5-Much of that deals with the surface shader being used, more than the lights themselves. What shader is it? Two different specular colors will blend together to make one new color, so that is what the specular only light shows.

6- For such a small question, it has a big answer. From Digital Tutors: "Ambient occlusion allows you to simulate the soft shadows that occur in the cracks and crevices of your 3D objects when indirect lighting is cast out onto your scene. The soft shadows that are created from ambient occlusion can help to define the separation between objects in your scene and add another level of realism to your render."  http://blog.digitaltutors.com/understanding-ambient-occlusion/

Put this into a Google search for further forum reading "ambient occlusion site:www.daz3d.com"

7-Yes they cast shadows, as MJC says the shadow softness is making them less noticeable, and the ambient light from the IBL is washing some of it away too.

 

Stryder87

DestinysGarden said:

1-Yes. the specular light was behind the person sort of close to the backdrop.

2-The IBLs are UberEnviroment lights. The rest are standard spotlights and distant lights.

3-A regular spotlight set to Illumination "On" will illuminate both diffuse and specular. Change to "Diffuse Only" and you get no specular highlights. Change to "Specular Only" and all you get is specular highlights. Change to Illumination "Off" and you get no light.

So, if you are using a regular spotlight just set to be on, the only way to adjust any specular highlights is on the surface itself, or by adjusting the overall amount of light, which may make your scene too bright or too dark. If your light is specular only, you can adjust either the surface, or the specular only light, without changing the overall amount of light in the scene. The basic set up on this particular set of lights was a standard photography 3 point system Key, Fill, Accent. There is a Key light set to Illumination On (both diffuse and specular), which is the main directional light source, a Diffuse Only light to Fill in, or brighten up, shadowy parts of the scene with out adding highlights, and a Specular Only light to Accent certain highlights. Some of the set ups have an additional Fill Light, Accent Light or Rim Light. The UberEnvironment IBL provides general, coming from everywhere, ambient light. It is like the wrapper on the package, the thing that ties it all together and makes it cohesive.

Yes, the same principles apply no matter what type of light you use. I guess I get wordy in the morning. Apologies if that was long.

4 &5-Much of that deals with the surface shader being used, more than the lights themselves. What shader is it? Two different specular colors will blend together to make one new color, so that is what the specular only light shows.

6- For such a small question, it has a big answer. From Digital Tutors: "Ambient occlusion allows you to simulate the soft shadows that occur in the cracks and crevices of your 3D objects when indirect lighting is cast out onto your scene. The soft shadows that are created from ambient occlusion can help to define the separation between objects in your scene and add another level of realism to your render."  http://blog.digitaltutors.com/understanding-ambient-occlusion/

Put this into a Google search for further forum reading "ambient occlusion site:www.daz3d.com"

7-Yes they cast shadows, as MJC says the shadow softness is making them less noticeable, and the ambient light from the IBL is washing some of it away too.

 

I think I just learned more about lighting in this thread than I have in the entire last 2 years! 

 

Stryder87

DestinysGarden said:

So, if you are using a regular spotlight just set to be on, the only way to adjust any specular highlights is on the surface itself, or by adjusting the overall amount of light, which may make your scene too bright or too dark. If your light is specular only, you can adjust either the surface, or the specular only light, without changing the overall amount of light in the scene.

Thinking about this, that would mean then that, instead of adjusting the surface properties, couldn't you just shine a regular light on the figure plus a specular-only light (or diffuse-only) on the figure as well and make the adjustments that way?

Regarding the two surface settings, the surface is an AoA SSS surface.  It has two Specular channels, one matching the colour of the Disffuse channel, and one that was solid black.  Not sure how a Spec light would affect that.

 

mjc1016

There isn't the same kind of control doing it with just lights.