Lighting Through Small Windows

[Wilyman]

Hi,

This is my first post to the forum. I'm hoping some of the lighting experts here can give me a bit of help.

I'm currently working on a visualisation of the chapterhouse of a cathedral, which is a large circular room with ten small windows around the sides.

Normally, I'd put a vray light in each of the windows, and maybe one direct light to show the sun coming in, and there wouldn't be a problem.

However, in this case, I need to show how the lighting changes as the position of the sun moves during the day, so I can't really fake it with lights in each window.

I've tried lighting it solely with an IES Sun, and a bluish environment (see below), but because the light for the entire interior is coming in through such small windows and having to bounce around so much, I'm getting incredibly blotchy images, even with very high irradiance map settings, and my render times are through the roof.

Has anyone got any ideas as to how I could light this, so I'd still be able to animate the sunlight, but without the blotches and high render times.

Cheers,

John

[plastic_]

i think i'd try QMC for the first bounce (because of the small geometric details) and lightcache for the secondary bounces (for proper illumination with infinite bounces).
or, if it has to be a longer animation, a layered/faked approach with multiple passes for ambient light and direct, diffuse lighting.

[vlado]

You can use v-ray lights in "light portal" mode; in that case they will be picking the color from the environment behind them, and will let the sunlight through.

Best regards,
Vlado

[Da_elf]

actually i find in these cases LC seems to be less noisy

[Wilyman]

Thanks

Thanks for the replies. I've been experimenting with them all for the last few days.

plastic_:
I'm probably doing something wrong, but trying QMC for the first bounce took an absolute age to render. Also, for the majority of the animation, the lights won't be moving, so I'd like to be able to bake the lighting in advance (i.e. using irradiance map, light cache, etc.), and so QMC isn't really an option.
However, your suggestion of using the light cache for the secondary bounces definitely helped, and obviously I can bake that too, so thanks for that suggestion.

Vlado:
Could you go into a little bit more detail on how to use the lights in 'light portal' mode please?
I tried putting a vray light in each of the 10 windows, with 'Skylight portal' checked, and although the rendering was slightly better, it was still pretty blotchy, and the irradiance map took 7 times longer to calculate.
I've looked in the help files and searched this forum, but I can't figure out if I'm using them in the right way.

Da_elf:
Do you mean LC for primary bounce? I gave it a go, but it seemed as noisy as the irradiance map, just with a different style of noise, if that makes sense!


Anyway, I've resorted to using vray lights in each window, but with a low enough intensity that you can still clearly see the direct light from the sun. It seems to be giving reasonable results at the moment. No blotches, other than on the plain white bits, which won't be white when I'm finished, and render times of about a minute per frame, which is fine by me.

Ignore the modelling and textures - both need a lot of changes. I'll post it as a WIP in the Image Uploads forum when I get a bit further.

Cheers,

John