Don't Use Emission Light When Making Scenes.
Cenobite
Posts: 206
Can people please not use this bad emission lights to light up a scene your selling because they are the worst light to use, they never render complete because the light throws white dot specks all over the scene and takes forever to render, the pic below is an example of emission render used in proper Iray daylight. You can see in the render below how the emission light leaves white dots that take forever to render while the rest of the scene is rendered clear in seconds because of the different lights used.
You need to create mesh lights & optimise the shadow the light throws off or the scene renders badly & takes forever for an unfinished look. Look at all the white dot at the enterence too the building, that should not render like that, takes an hout to render this garbage light why use it in professionally sold assets.
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Different lights are appropriate in different situations. The Iray Sun/Sky or HDRI, whichever you mean by Iray Daylight, isn't going to be useful for interiors - after all, if it were it would have worked for the interior space here. Interiors, especially with shadowy nooks, are simsply hard to light well.
This is a viewport render of a scene lit by a single emissive light, a 1 meter primitive sphere. Looks fine, renders in seconds.
PAs can certainly create bad light presets, but emissive/mesh lights work when used properly.
Why does emission light take so long to render and how can i make emssion light effects smoother & not cast all this fragmented light speck everywhere?
Emissive mesh lights are a different kettle of fish when setup properly, they have optimised shadows where if you say just use an emissive shader just to highlight certain objects like light globes or other surfaces to produce light they don't factor in smoothing the light & adding shadow smoothing for each light particle thrown off or onto the surface. So what i mean is if i just go too smart tab lay a surface down with say 7k lumens whatever that means in watts and it produces light in a limited area the light cast off this shader casts this hard particle that when the light reflects off objects it pixelates causing firefly giving that unfinished render look. I totally agree correct mesh lighting it best to use because you won't get this distortion in the finished render that just using an emissive shader on a surface produces. I find some of the environment stuff sold has bad lighting issues while you can produce a render out of the box they are not optimised for best render outcomes, you basically have to replace all lights with your own lighting if you want top notch renders.
An emissive surface sends out one path per iteration for each polygon - if the surface(s) with emission have a lot of polygons that will slow each iteration down, without directly addressing the need for light to reach shadowy areas (which is a matter of placement and number of lights, and of the source's size).
Emissive mesh lights are just mesh with the emission colour made non-black - there are not two different kinds of emissive lighting. As I said above, it's a matter of placement, size, and number of lights; speed is a factor of the complexity of the emissive surface(s).
Of course point and spot lights don't have to be points, they can be given a range of shapes in the light properties (sometimes it makes more sense to use a light with a primitive shape rather than have a surface emit).
the underlying mesh topology of the emissive surface plays a huge part in how well they work too
some sets are just not up to the job, subdivision can help, flipping normals if reversed helps too, triangulating if it has Ngons
Depends on the scene. I don't have the Egyptian Oasis set, so I can't say what the issue is exactly, but generally you need to adjust the size and lumens of each light until they're all balanced without under- or overexposure.
I like to fill the space with 50cm spherical lights to give it a nice diffuse ambiance. The mood of the scene will determine how bright I make them (spooky vs. sunny). That way, Iray has plenty of light rays to process.
You can try placing a ghost light inside the temple.
Or you can increase "quality" and "max samples" in render settings and spot-render just the grainy part.
Yeah but i have tried using point lights and focused spot lights in badly lit scenes and still get poor renders or light that shines too bright on areas while leaving other areas looking unrendered not smooth looking. The render i did below i have thrown every light source at it besides making up a mesh light large enough to throw light on the entire scene yet it still renders with haze, i get better quality renders with other scenes that have used light better.
I placed point lights in 3 areas for each character plus focused a spot light with widen beam that reachs to the back of this scene, every light i add just adds more specks that takes longer to render yet never gives me a clear render where if i use an outside distant light source i get a super fast highly detail render that looks clean in seconds or minutes not hours. If you use a super bright light source it has to be positioned far away or it just washes out the scene with too much light killing the whole render.
This first viewport render was done using a point light with its geometry set to 50cm.
This one was done with a spherical mesh light set to the same size and lumens.
There's almost no difference. The image isn't any noisier.
Now, this viewport render was done with the environment's diagetic lights, the ones built into the ceiling.
This one shows a lot of noise.
However, if I set the Max Path length to 2, so the light rays only bounce twice, the problem goes away.
So it's not necessarily mesh lights that are the problem, but the number of bounces they need to do. I presume since they're on the ceiling, they're not properly positioned to hit all the crevices (as Richard said).
Now here's the scene with both the diagetic overhead lights and the point light (with the lumens decreased) at the same time.
Still somewhat noisy, but getting better.
Finally, here's the overhead lights, the point light, and the mesh light (moved back so it lights up the dark areas).
It still has some noise, but not nearly as much as the overheads alone.
So whether you use point lights or mesh lights doesn't matter. What matters is where they're positioned. Blanketing your scene with centralized point lights helps reduce noise created by diagetic mesh lights.
Since these are all viewport renders, obviously the problem will diminish the longer your final render runs for.
There can be a combination of factors that can cause your "white specks" in a scene, and lights are often just one of the issues. Shaders that are too reflective for a scene lighting can also do this. I've found the most common cause to be a combinations of shaders and lights. the shader simply being too "reflective" for the light needed in the scene. The root of this problem is there is not a lighting standard for the development of products for sale here (and elsewhere). The creators use their own light set ups, and make their shaders work properly with them. Sometimes when you put the the figure/prop/etc. in different lighting environment it simply doesn't work as well as expected. To reduce the white specks, you need to either reduce the brightness of the offending light(s), and/or reduce the reflective properties of the shaders for the surfaces that are creating the white specs. It's quite simple, but sometimes a bit of a balancing act to get the light you want and the reflective/shiney surfaces you want as well.
The other issue with the Oasis scene isn't the same. In this case you are seeing what is often referred to as grain or graininess which happens in low light scenes. There is no one size fits all to fix this, but here are a couple of approaches that I use to address it. The easiest in terms of work for you (the user) is to just increase the time allowed to render the scene. To do this, change "Max Time to 0 (zero) in the Progressive Render settings. This will allow the scene to reach full convergence and eliminate all (or most) of the noise/grain (I just looked at that set last night, I'm sure it will work for the interior). Keep in mind though that the default value for convergence may need to be increased if you have an area that is a focal part of your image that is still grainy after 95% convergence. This approach can lead to very long render times, but it is the simplest approach.
The second approach is to increase the scene lighting for closed environments. My favorite way to do this is to use an "Iray Sectional Plane" and an HDRI. You use the Iray sectional plane to make the portion of the environment behind the camera "invisible" which allows the lighing from the HDRI to ender the scene. This can provide a nice fill light for your environment without adding a lot of other lights to the scene, and speed up render times.
Finally a very popular method for reducing grain and/or white specks in a scene is to either user the Nvidia denoiser included with Iray, or use and external denoiser to reduce the noise after you render the image (there is a good one from Intel that a user here has written a script so you can use it with DS (https://www.daz3d.com/forums/discussion/438007/how-to-use-intel-denoiser). I don't use a denoiser because they tend to smooth the details more than I like (there are some that work extremely well - like the one in Octane Render, and people really like the Intel one as well because it does a very good job), so I really can't give you and tips on this process.
If you're interested, you can look through my gallery(s) and see if there are any images with lighting situations you might be interested in. Most of my more recent images (last 2-3 years) include a little bit about the lighting set up. Not extremely detailed, but enough to give you an idea about how things were done and it might give you some ideas.
i think if anything, the most important take away I can give you is that 1) like others have noted, mesh/emitter lights aren't bad, but are quite effective when you understand how to use them and 2) shader settings can be very important to getting a good clean image in the lighting you want to use (sometimes just one item in a scene will need to be adjusted to work with everything else, and other times most everything needs a bit of help). The most important thing to do is to learn more about lighting. DAZ has made it incredibly easy to just drop stuff into a scene and hit render and you get a decent picture. However, as you incerese scene complexity you really need to learn more about lighting - the best reference for this I know of is: Digital Lighting and Rendering by Jeremy Birn.
Below is an example of using 2 Iray Sectional Planes and the default Iray HDRI (Ruins HDRI) as the primary lighting source to show you don't need overly complex lighting to get a decent image. the light saber and the drois ligts do contribute to the lighting, but not a lot. The bloom effects were done with Iray and not post processed. (Note: There is fog in the background - not render noise.)
Here is a scene that just uses emmisive lights and one spot light IIRC - not the greatest composition, but no white specs!!
Edit: It does use an HDRI as well, but it didn't contribute much to the lighting (no Iray sectional plane was used), it was used to give the bokeh lights behind the open door.
This scene just needs to render longer. It has an insane number of maps, I´m guessing you´re CPU rendering? It think it will take forever no matter what you do.
You could help by "cutting off" the ceiling and some of the walls with IRAY section planes, and place a low-contrast HDRI.