Noob question about lighting (updated with image)

[tukor]

Hi there!

Im making a scene with only an emissive mat as lighting.
The mat has only emission node, texture emission; wich has a gaussian spectrum and a float texture for distribution
The thing is... first, it makes A LOT of noise .........
And second, if i turn on a light (a sky for example) it changes the color of my emissive material...why is that?

Just tryng to learn. Thank you!!!

[tukor]

Ok im lost with this, so im giving more information and images.. and lets see if someone has any recommendation

What im doing is a Game of Thrones style Intro, for a animation with a map i made for my city.

For now, im just playing with it to see how can i do it; As you can see in the next image, some materials are just white (placeholders), i have not finetuned the post or anything. I just want to know if i can render this thing with those lights.

The SUN in the center (as well has the eyes, mounth and the letters, have a emissive material.
It only has:
in Emission: blackbody emission
in the blackbody emission, in texture = GaussiaSpectrum = wavelenght 075,width 0.04, power =1
For distribution, it has a float texture

"power" of the blackbody = 100
i think its where the troubles may come; 100 seems to much, but i like how it glows.

There are no more lights in the scene.

This is the result, after 45 minutes (!!!!!) of rendering. Path tracing 10000 samples
I CANT afford 45minutes per frame.... And it still have a lot of noise.




What should i try, please?

[Lewis]

how many GPUs you have and what is your GI Clamp value ?

[tukor]

1 GPU, a 980Ti.
GI Clamp was maxed lol... thats was one thing.
Now at 4 its much better, i also changed more things.. Still 20-25min anyway

[tukor]

Also, if i want to give it a touch of light (just to give it more light to darker zones... how would i do that?

If i add an sky or something so, it chages completily the lighting... not matter i gives it 5 power or so...

[Lewis]

I think you could clamp it to 1.0 (default is like 1 million or so) in this scene since so it'll help with fireflyes and it'll speedup render even bit more.

But frankly with 1 GPU you won't be getting very fast PT render times with 10k samples. That's simply not enough GPU power for 2-3 minute/frame .
What is your target/possible to render time per frame ? Considering that clamping GI has already halved rendertime it's good "fix". Now if you buy 2 more 980Tis you will get 7-8 min/frame in current state .

P.S. do you have Adaptive sampling ON ?

EDIT: For more light add exposure or use some of Color profiles

[tukor]

Hey There! First of all, thank you a lot for taking the time to help me!

3 x 980Tis... woww that would be like a dream! Unfortunately, Its not possible for me to buy more Gpus, it took almost 3 years to get the cash for one...

If i set clamp to 1, then the image gets darker... with 3 too... I dont know if i just can compensate with exposure; im reading about the render settings and trying to figure it out.

I activated Adaptative sampling, and in a 10min render it went to 9 minutes; so i got 1 more minute (wich in larger renders would be more).

I dont know if part of the problem could be the lack of light except in the areas lightened by the emissive mats.
And i know i can give these mats less power, and probably i would get less noise; and then use "bloom" to get more light. But bloom does not the same effect, as it gives light all over the meshes, in places where it should not be.


In the end, i think you are probably right; i would need more Gpus... but anyway, if there are more tips you can share, ill be glad to hear it.

Thanks!!!

[Lewis]

Try adding imager and more exposure and try to play with "repsonse" filter to get more bright/different look scene. I usually like to use DSCS315_2 but others might work for you too.