Light and emission in Daz3d help needed
KTR
Posts: 8
Read next :)
Post edited by KTR on
Daz 3D is part of 
Connect
DAZ Productions, Inc.
7533 S Center View Ct #4664
West Jordan, UT 84084
Licensing Agreement | Terms of Service | Privacy Policy | EULA
© 2024 Daz Productions Inc. All Rights Reserved.
Comments
Hi Im fairly new to Daz3d and was doing some lighting test with the emissive shader, however I ran into some issues and hope someone can help me.
I use a very basic setup which is a Sphere and a plane, the sphere is the only light source in the scene. I tried to add images, but not really sure if I did it correctly as I seem to only be able to add thumbnails, but hope it shows what I mean anyway.
Basic setup
1. This is a shot directly from the top through a camera.
For some reason the light is square instead of round, how do I change it, so it cast a round light like a point light? Here is an example of what a point light looks like from the same position
2. The next issue happens as I move the sphere closer to the plane, depite the square light and the odd black line (think it might be from the plane) it looks fine.
However as I scale down the sphere is starts to cause problems.
The square light gets very visible but also the size doesn't seem to match the light. Will get into that some more next.
I changed the sphere to a plane also using a emissive shader and placed a sphere in the scene just so it have something to shine on and it looks fine, there are a bit of fireflies which might not be possible to see in the thumbnail.
When I descrease the size of the plane, a lot of fireflies starts to appear. How do you get rid of those, when using small lights? Lets imagine I was making a lightbulb for a lamp.
As I decrease the size of the plane and decrease the luminous efficacy (W) I still have a lot of fireflies but also it becomes very obvious that the light that the plane is casting does not correlate to the actual size of the plane.
So to sum up all the questions:
1. How do I fix the square light?
2. How do I get rid of fireflies when working with small emissive light sources?
3. How do I make the light that is cast match the actual size of the light source?
Hope someone can help and its possible to see what is going on in the thumbnails.
Are you using the default Iray shader on both spheres and the plane floor, on everything?
On the plane emitter, check that it's set to single sided.
With the current release, 4.9.4.122, I am not getting any squares edges or lines!
The plane is using an Uber shader and the sphere a emissive shader, I have tried checking and unchecking the two sided made no difference. However I think it might be a bug or something.
These are the settings I use
Enviroment intensity = 0
Enviroment mode = Scene only
For the sphere:
Emission temperature = 6500
Luminance units = W
Luminous efficacy = 2 or 5
Scale of the sphere is 2% and move it just slightly above the plane.
The plane just uses a standard Uber shader.
Did some more testing and it seems to happen when you scale the plane at 100 - 200% it seems fine, however if you scale the plane to 1000% I get the square lighting and the black line.
Nope, I still can't reproduce that.
Have you got an Emission profile active, that might be set to a square shape?
(I tried the Emission shader, just in case it was different, generally I just switch on the emission in the Uber shader.)
On the question of scale what is the actual size of the objects, I wonder if Iray breaks if you make the emitter too small.
Thats weird, I tried to load an emission profile and it changed the light, but the issue im having have no profile active its pretty much as basic as it can get, I think.
Im not sure what you mean with actual size, I just add a standard plane in Daz from the top menu and set the size to 1000% and the same with the sphere which I set to 2%. I havent changed any scaling settings in Daz (If thats possible :)) Its a complete new scene.
Try making a small sphere instead of scaling and see what happens.
Some random thoughts:
1. Move away from watts as the units. It doesn't match any other type of light in D|S, and while designed to help you mimic "real world" lighting, its implementation tends to simply confuse people. Choose cd/cm2, which is candles per square centimeter. This option matches D|S's own units of measure for everything else.
2. You should always, at a minimum, choose the Emissive shader from the Iray Uber collection. This shader unsets a number of potentially conflicing shader options that are either not needed for emissive lights, or can cause contradicting output values.
3. It's better to render your scene with lights and backdrop only, or else the results will be affected by anything else reflective in the scene. So, if you're wanting to test the area of planar lights, get rid of the sphere, as its reflection is also contributing to the lighting (albedo) in the scene.
4. Keep in mind that unless you use IES profiles, light emitted by emissive objects is projected in 180 degrees from the surface of that object. Therefore, there will be some light that seems to appear to come from the edges of the geometry.
5. If you want to direct and control the lighting from an emissive object, use an IES profile instead. You can find these free on the Web from most any light manufacturer. Apply the profile and do a test render.
6. If you want controlled lighting from a geometry, try a spotlight or point light instead, and select a geometric shape for the emitter type. The default for both is point, which means an infinitely small source. You can set the size of the emitter as needed (units are in centimeters). A downside to this method is that you cannot directly see the size of the emitter in the default shaded scene view. You need to render the scene to see the actual size and shape of the emitter.
I tried making a 10m plane and a 0.1 sphere and that seemed to work. However it still occur if I import an object. I tried making a quick sphere where the 3 lines around it will be the emissive light and the rest will have a metal shader. Lets imagine it was a lamp of some sort.
So I place it above the plane as before and render it and I get a square and a lot of fireflies this have rendered for 2 minutes I think which aint a lot. but will get into that next.
I have tried to scale the sphere inside Daz and then export it as an obj file and import it again but that didnt change anything. Is there a way to check an object actual scale inside Daz?
The next thing is emissive light and metal, again lets imagine I was making a lamp with a metal lampshade. So to simulate that I made 4 spheres with car metal shaders and a smaller sphere in the middle with a emissive shader and this is what it looks like after 6 minutes of rendering.
At the edge of each light there is a ton of fireflies, how do you get rid of them? Rendering for 6 minutes, when the scene have 4 metal spheres and still a lot of fireflies is a bit annoying, Imagine if the scene had a lot of cars or metal objects it would never be done.
This is starting to turn into a nightmare, I thought something like this was straight forward :D
1. I tried changing it to cd/cm2 and it made no different its still a square.
2. Im not sure what you mean, I use the Iray emissive shader, but I tried adding a Uber shader and use the emissive channel in that one or what to call it, if that is what you meant? But its the same its still a square.
3. Not sure I understand what you mean, there is only the plane and the sphere in the scene, the sphere is what is casting the light and the plane is just there so the light have something to hit. The plane uses a standard Uber shader, so I havent added or change anything to reflect anything.
4. I can see I could use a IES light to give the light some profile, but i just want the sphere to cast light in all directions as you would expect a sphere to do, as it also do under some circumstances. The issue is when it doesnt but decide to make a square. Shouldn't the sphere I made, regardless of me using a iES profile or not, at least cast light in a circle rather than a square, that is what confuses me.
5. I don't really want to control the light, except through the mesh of the object. So the edges of the sphere where the lines are should block the emissive light comming from the circles. but it doesnt seem to do that, as it just make a square of light.
6. That sounds interesting, can I make it cast light from the rings? Because what I need is for specific faces to cast the light, not just the whole object. If that makes sense.
Here is an example of what I mean, Its the same sphere which I imported into Poser and scaled to 1% and place right above the plane so its a similar setup, I made the rings emissive and the rest of the sphere is set to a 100% red reflective metal surface.
As you can see it doesnt exactly look interesting, which is fine its just to show what I mean, but the light is round as you would expect, which is what I need in Daz as well.
Attached is the simple scene I'm using (no ringed sphere).
I've also tried a ringed sphere with Iray settings applied to it.
KTR, the more polygons your emissive surface has, the longer the render will take, because the light from each polygone is calculated independently. That's why tools like Ghostlight use single polygone emissives.
To make a light cast "square" shadows, you'd need flaps around the light, just like a real light equipment used in a real photo shooting. An example is this set: https://www.daz3d.com/ig-iray-stage-lighting
Otherwise, light will radiate away into all directions from the surface, just like real light.