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Petros Proestos avatar image
Petros Proestos asked ·

No shadows with mesh lights

I have a lot of complaints from my partners that my final renderings are not producing shadows. In this rendering I don't use any quad light or spot light. I only use mesh lights, means that where you see lamps, these are objects assigned as meshes to mesh lights.

If you notice down the image, the chairs and the table are not capturing shadows over the floor. I keep all mesh lights values low (illumination=1 and exposure=1) and also I keep low the global exposure (environment dialog) with a value of 2.0 EV.

Do I have to stop using mesh lights and using normar arnold lights like spotlights ecc or is it something else?

thanks for any answers.

Cheers.

mesh lightsno shadows
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Mads Drøschler avatar image
Mads Drøschler answered ·

Look here. I illustrate your problem. You have too much ambient light going in the room, I enable a skylight to show you the effect of having too much ambient light going in a room at the cost of loss of contrast and more importantly in your case, loss of shadows, they are washed out completly.
Your lights are sending out too omnious light and you need to control them
All your lamps contribute too much to over all lightning and it will blow out shadows instantly if you get so much light from all angles.
https://imgur.com/a/5qdrlJo

Also it looks like there is a skylight or some huge window behind the camera, contributing to a ton of light, that light will instantly wash away any weak light, and your long and circular lights are very weak.

Simply put you got way too much light bouncing around in the room.

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Mads Drøschler answered ·

The mesh lights are fine.
Your image is extremly flat meaning middle tones are completly dominating, so you lack contrast, and that is what shadows versus highlights are.

In post you can simply raise the blacks significantly and dial back the middle as well to gain even more contrast, which will bring out all shadows in return.

So you need to work with the final render and make it "pop" after rendering is done.
I made an example here, lowered the overall lightning a nodge but greatly increased the contrast.

In general you use the "levels" filter, and in general you move the 2 most left flags to the right.
You need to play with it and you need to be way more agressive on grading than you think you need to, to lift it out of the pale and uncontrasty environment that, atleast for this image compeltly dominates the feel.
This way all shadows steps into character and all transitions between shadow and middle are more clear.
While doing this on a test, you may find your post correction sits nice, but some surface some specific place becomes to dark, this is where you either use a mask to feed the surface back, or simply just lighten it in the render application and rerender a final.

As for lack of shadows under chairs, well, your lightning dictates it, so you could for example just lower external light, or increase the artificial lights and lower exposure to create more scene contrast and less "everything is evenly lit" nothing is never ever evenly lit in the real world. It is full of blown out highlights and crushed blacks.

Also considder how you light the set, it looks like there is light coming from behind the camera, that will blow out any shadows under the chairs for sure, light fixtures can be incorrectly modelled giving a much more omnious and less directional light than the real one, I dont know, but check up on that.

So you need to balance it out a bit better with light intensities in the render, and then crank the blacks up in post.


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Mads Drøschler answered ·

I would leave out those beams of light from the sun entirely.
Try look at the shadows under the first chair, the shadows from the ceeling lamps are overwritten and cant be seen, you only get the sense of the sun indirect and direct shadows.
So you kinda destroys the attempt to make shadows under the chairs with that setup, I would not use the direct sun as previsouly described, it also sits on a very bad angle.

Also, push the saturation up and crank the levels blacks and mids.

I like the shadows under the first chair better on this one where you took out the sun.
I can see denoiser patches at the top green arrow, be aware of that so increase denoise quality if you are going to push the image around in post.

I would turn that giant bright light down in the other end, off, it steals focus and actually lets the sitting area not-focus. So just give the rear end some neutral lightning, it will also clean up the scene and make it simpler, the simpler it is, the better.
It also gives a ton of blue light, which conflicts with the warm base colors from the scene. So we get that artifical Blue/red feel going, it has to be suddle, and gentle.
Its alright to have a big giant lit area in the end, if it serves a concrete puropse, but its not a purpose alone to just feel that you need to put some lights in because its dark, but dont overdo it and steal focus on something irrelevant, the lamps and chairs are main focus, so lower or delete that light that makes the backwall go pure white, in return you can then crank general exposure up and give chair area even more focus.


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Mads Drøschler answered ·

Then turn the big lamp down in a seperate setup so they dont share same intensity as the rectangle, and color the lamp pure white with emission 1.0.
Dial them in till they sit nice with the first light, because yes, that is far better contrast is much better on first image. But you can use mesh light fine, just turn down the big one.


Now, only dial in the big ring, remember its a much larger surface so if you power the same through as on the rectangle, you get too much light, just a little bit, watch the shadows when you render a rectangular shape in active shade, where you also have some of the wall in the rectangle so you dont over do their power.

Just phase them in from 0, give solid color first on emission so its always white, then slightly increace wwith the spinner and render window updates fast with right settings.

Be gentle with the big light, it very easily overpower the long rectangle, and we have to remember the mission, your partner wanted nice shadows under the teapot, so dont kill them with the big ceeling lamp giving it the same output as the rectangle, less is more.

2 different setups for the 2 mesh lights in the ceeling. 2 different exposures, you would want to add supportive light to your master light, which is the one giving nice shadows on chairs. Now, all other lights are just supportive lights. meaning they come in from below and stop some place where they dont destroy main focus point, which are chair shadows. Workng like this you can quickly create small stories here and there in images on request and you get some training in setting up custom focus points.

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Mads Drøschler answered ·

To me?
It looks like green arrows are light shafts in the building to the right side, probably 3 or 4 pillars with a view outside - and a sun.
- You wash out all visible shadows in addition to the other points mentioned, since light comes from roughly same angle as the view, all GI shadows starts to get biased in that angle, especially if its strong, but right now, its just uncomfortable weak, it feels like there is some sky light that is helping blowing shadows in this worst possible direction or close to, since its not a lamp that sits on the camera, that would be the worst ever angle. Blair Witch, running around in forest on mushrooms hyperventilating, 1 guy falls down into a hole and something touches his legs as he hangs with torso up at the forest floor.
I personally try to aviod those automatic negative associations if possible.

So chairs shadows from ceeling light suffer from this addition.

It feels like you create too many lightning aspects inside the same exposure range.


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Mads Drøschler answered ·

Your image in general suffers from this condition:

So and there are no actual render settings touched, its just grading, notice the insane difference.

Now pair that with multiple lights and those weak shadows gets washed out very fast.


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Mads Drøschler answered ·

Try close all lamps down, everything, all of them, zero.
Then enable the long rectangle, and you will see super shadows under chairs instantly.
They get gradually washed out because you keep adding in lights in the same spectrum, so they all compete with each other, in the same area of the light band.
There are no strong and weak lamps, they all sit and emit the same amount of light.

Now pair that with lack of crushed blacks and nice highlights and you got the recipe for a bland and uniform non contrasty image, you need to work on several parameters and you need to understand that the more lights you add in, the less sharp shadows you will get if they are too weak, and you compensate by raising some general exposure, or worst of all, mid tones way up "to try make the image brighter"

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Petros Proestos answered ·

@Mads I deleted everything leaving only the quad light from the long linear roof

light in the top-front. But I did make the quad light not long as the real light is, but shorter.

With this result I think I have the shadows I wanted...

What do you think? less is more finally :)


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Petros Proestos answered ·

These are my modifications to the lighting system. Deleted all lights and leave only the skydome+portal at the first picture and at the second picture playing only with the big rectangular light on the ceiling. Main purpose to show shadows as much as I can... Any thoughts are welcome again...

Physical lighting only:

Artificial lighting only (and a littile of skydome lighting):


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Petros Proestos answered ·

It's incredible how fluent is your english @Mads :) :) :)

As you understood, I've been a little lazy with arnold lights :) :)

I've found so much quick and convenient mesh lights, that

I decided to assigned them to every lamp (object) and turn them all on!!!

I know, you are totally right, big mistake to overilluminate with any kind

of artificial light (not only mesh lights) + extreme ray bouncing + very

bright skydome lighting + I wanted to "cook" everything together: exterior+

interior lighting (at the wrong camera angle), because at the end the result is awful.

So!

I have to create a lighting scenario (the little stories you say) each time

I render a scene, because in Achviz, shadows are way too important to show

because they give that three dimensional feeling that everything pop out the picture.

I close one year using Arnold (ex mental ray user), I was impressed

how fast is Arnold to give awesome results, but that speed make me forget

the art how to use lights... Because at the end... we create art.

thx once again for your wise advices Mads, I hope my next rendering I post

here will be flawless.

*ps: I avoid post production. I believe that if someone is good to use 3d software,

the render image by it's self must be enough. Especially in out times that

out bosses requires everything with light speed... :)

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