Ghost lights and reflections?
handel_035c4ce6
Posts: 460
Does the ghost lights actually reduce the reflections?
Post edited by handel_035c4ce6 on
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Ghost lights don't appear in reflections, if that's what you mean - theya re almost invisible, which is what makes them ghost lights. They don't stop other elements from appearing in reflections, though.
Can you give us an example of what is happening that you want to change?
For example, are you seeing a hot spot on an object where it is reflecting the existing light? Or do you have an object that is reflecting the things around too strongly?
So if a human body is uliminated mostly from ghost lights. will it be less reflective then if iluminated by environment light (with the same overall intensity ofc)?
It will be just a reflective, but the lights themselves won't be relfected as they are hidden - anying else, however, will reflect normally.
I think this is about the lack of speculatity when using Ghost Lights. I normally use a spotlight as well as emissive lights if I want to show shiny surfaces.
Yes, that's why I've been stressing that the lights won't show in reflections.
Ah, right. I geddit. :)
What you mean under "emissive lights"? Isn't every surface which has "emission" enabled a ghost light?
Also does the other lights which have "dimensions" work like the glost lights (not reflective)?
In Iray, "Mesh lights" are objects, or parts of objects, that have Emissive properties. "Ghost Lights" are mesh lights with the opacity turned really low, while still having some opacity. (Cutout Opacity: 0.0000001, for example.)
The reason for using Ghost Lights is to brighten a scene without adding a "hot spot" like you'd get with a spot light.
Your eyes adjust to the light in any given space. Pupils dilate to let in more light or shrink to restrict the light. If you walk into a typical bar, for example, after being outside on a sunny day, the room appears to be very dark, with a few bright spots where lights are. But once your eyes adjust to the dim light, the room seems to be lighter, and most of the details become visible.
If you light a similar bar scene in Daz Studio using real light values, chances are your render is going to be really dark with a few bright spots where the lights are. Using a ghost light in such a scene will brighten the overall scene much the same way your pupils dilating will allow you to see better in a dim light enviroment.
This helps in two ways. 1) Iray takes a lot longer to render dark scenes, so the added light will improve the render time and 2) The scene will look much more realistic as all the specular and reflections will all be off the real lights in the scene.
I hope this helps.
Thnkas for the "ghost lights" definition. But actually I don't get specualrity with mesh lights too. Something else confuses me too - body shaders use PBR/roughness option and there is no specualrity even with with mesh lights; on the other hand the dress on the same body uses PBR/Glossiness option and the specularity ot it is working as intended with mesh lights.
First, the mesh lights with 100% opacity will always have the potential of creating specularity on the objects they are lighting. How much specularity will depend on how direct the light is hitting the object, along with the materials settings of that object; As you are seeing with the figure and the clothing. It's the same light, but the two objects are reacting differently.
There are several material settings that control how the skin materials reflect light. I'm not an expert on skin materials, and the vendors all have their own favorite "formula" to get the look they intend. It would be helpful if you could show a screenshot of the material zone settings for one of the skin material zones of the figure you are currently using; Arms would be a good choice.
If I can see what the vendor is doing, I may have some suggestions for how to get a higher gloss on the skin. And if I have the character, I can do some testing on my own. Of course, I need to know which character it is. (If the character is from other than Daz, I probably don't have it, though. I've only a few from other stores.)
I will post shortly 2 renders with the basic G8F and with the same shaders; one render in the vew port and another in a box from primitives and couple of mesh lights.
Voila:
They have the sane skin and the same shader wich should make the skin quite shiny - what can be seen in the left (viewport render); in the right the render is in a box of primitives with 2 mesh lights (100% opacity) at the ceiling and at the front of the figure. There is no primitive on the left hand of the figure and there is a HDRI outside. The difference between the specularity of the both renders is obvious (besides the maid uniform).
Okay. I'm going to test and see what I can find. I'll use an outfit the comes with Daz Studio. (I don't have the maid costume.)
The maid costume uses PBR/Glossiness, this is the main difference between the skin shader and the costume shader.
I am not getting the same results on my G8F skin. Can you attach your duf scene files to a post, so I can load them? (It won't matter that I don't have the costume. The scene will just load without it. What I want to see is the skin material settings.)
Tjhere it is - not absolutely the same scene but the results are the same. The 1st scene is G8F with 3 mesh lights and a camera (headlight is turned off). The second one is the same G8F. There can be seen hints of refelction on the render of the 1st one, but the same skin with the same shaders has a lot of reflections when rendered in viewport w/o camera and lights
I'll going to check these out, but I do want to point out, when you are using the Perspective View "camera" to render in the viewport, it will use a "Headlamp" in a default position. You can't control it. While I'm checking your files, you could select your camera in the Scene tab, then go to the Parameters tab. Look for and set the Headlamp Mode to On. It will be Auto by default, which shuts it off when there are lights in the scene, (spotlight, distant light, etc., not mesh lights.)
See what happens when you render the scene in the box with the headlamp on…
My problem is not the headlamp but rendering with mesh lights (which I thought were the ghost lights) - even if they are not ghost lights (because they have 100% opacity), they still make no reflections on the skin.
I've got some images for you. Hold on…
These are all from starting with your Test-shiny-camera.duf file.
First, I loaded the Basic Wear 02 that comes with the Genesis 8 Female Starter Essentials onto the G8F figure, so my renders will be TOS compliant.
Renders:
(I recommend loading the attached images into separate tabs, so you can easily see the changes by clicking on the tabs.)
As you can see with this progression of images, the mesh lights work better for shine/reflection at smaller physical sizes and larger Luminance values to compensate for the smaller size. It also made a difference having the lights facing the figure. (More on that in the next post.)
When you create a primitive, the dialog allows you to set the Axis Orientation. It took me a long time to figure out the differences.
As you are using the Plane for your mesh lights, I'll use it for my examples:
Selecting an X orientation will load the plane vertically, with the front and back of the plane facing to either side (left or right,) of World Center.
Selecting a Z orientation will load the plane vertically, with the front and back of the plane facing to forward and backward of World Center.
Selecting a Y orientation will load the plane horizontally, with the front and back of the plane facing up and down from World Center.
Choosing a Positive or Negative orientation determines which side of the plane is the front facing side, and which is the back facing side. This is important with a mesh light because, as shown in the previous post, it really does make a difference, even when using a Two-Sided light setting.
Looking at World Center from the Perspective View default, moving an object using the Parameter tab and the Translate settings will help you to understand Positive and Negative on the Plane. Select any obejct with X-, Y- and Z-Translate all at 0.
Move the X-Translate to a positive value and notice the direction the object moves, That is the direction of the facing side when using the X-Positive orientation. Move the X-Translate setting to a negative value. The direction the object moved is the facing side when using the X-Negative orientation.
Feel free to do the same with the Y and Z translate settings, but I know you see where this is going.
I'm serious, it took me a couple of years for this to sink in. Once it did, it made my 3D work much easier, But do know the tool you are using to move things around in the viewport is not going to clue you in to the orientation of your plane, or other primitive. It might help to add the orientation to the name of the object for reference. For example, Mesh Light X-Positive.
Wow! A serious testing:-)
Is render 4 still with headlamp ON?
So - the main question - it appears for the mesh lights to "cast" reflections they need very high luminance and thus their size must be reduced repectively and the option for luminance per sqm changed respectively? Definitelly will try it ASAP. Basicly I was making the mesh light larger to ensure more equal luminance on the whole scene to evade the dark spots but as the props are easily rendered having darker spots should ne be a problem.
As for what you wrote in the top of the topic about using spotlights for reflection - aren't the spot light too "concentrated" on small area and thus making it hard to achieve enough light for a close up figures?
For Image 4, the Headlamp is Off. The mesh lights have been turned to face the figure, and moved up so the bottom edge is on the floor. For Image 5 the planes are not moved, but by making them smaller, the bottom edge is higher in the scene.
Spotlights can be highly conentrated, but they can also cover a large area.
In the Parameters tab, you can also control other aspects of the light. In this image I recently created, I wanted the light to be concentrated on the central figure, but not spill out over the rest of the image. I'd never done it before, so it was all experimentation. It seemed a bit counter-intuitive to me The larger the Spread Angle, the more the light is distributed across the scene and the less bright the light emitted. But then increasing the Beam Exponent made the center brighter, and actually shrunk the area that was lit.
I recommend you take some time to do some experimenting on your own. I've been working with Daz Studio for more than 4 years, and yet I only discovered the Spotlight could do this effect in the past month!
I've also been corrected on this statement. You do have the ability to turn this Headlamp Off by setting Auto Headlamp to Never under Render Settings->General.
However, when using an actual camera, if you want to use the Headlamp, you can also control where it is in relation to the camera, (X-, Y- Z-Offset,) and the intensity of the Headlamp. These controls are not available for Perspective View.
Thanks a lot. I still have problems with the light because I started to use Daz aster I got used to Blender and in blender the lights kinds straightforward compared to Daz.
Did you ever tried to use the point lights as portals (this makes wonders in Blender), but I read the portals are somewhat bugged in Daz?
I have not.
I got started in 3D with Daz, and I've gotten "almost" comfortable creating morphs in Hexagon. I open Blender, attempt something or other simple, like rotating the view, realize I'm in way over my head and close the program. I then slink out of the office to go watch a couple hours of paranormal stuff on cable, (my hubby's new vice,) and after a few hearty laughs I come back in and head straight for Daz Studio!
In Blender the RMB and LMB by default are interchanged, but there is an option to adjust them as you are used.
Went right over my head!
is that Right and Left of whatever MB stands for?
Edit: Wait! MB… Mouse Button?
Yup:-)
Leaving aside the hideous possibilities of Blender as 3D program, one of the best feature is you can get a real render preview in real time and make adjuistment as you watch how they change the renders even with my measly old 2GB GTX 650 . On theory IRay can do this too but...
The problem I've found with ghost lighting is they can in some cases still appear in reflections, especially on mirror-type surfaces. Also, when you lower the opacity of an emissive surface, it's usually necessary to increase the lumens in order to get the same amount of light output.