Natural Sun Lighting Through Windows, Interior Room Too DARK

Question

I'm trying to model my apartment for a restoration. I can't get the outdoor natural light of the sun. The scene remains always too dark and full of noise fireflies.

As you can see from the photos the sun was not even so bright, but the interior of the apartment is completly lit.

This is the result of my render: I'm using an HDRI image as env. texture.

Can someone fixing this scene, dark room and noise? Has blender a limit?

I really couldn't find any answer, every similar question on internet has no answer.

I tried to tweak the exposure value, env. texture strength, light bounces, light clamping, sky texture, portals on windows, transparent material for windows with no results.

I'd prefer not using fake lamps but let blender simulate the natural light physics.

Answer 1

Hello dear Blender community,

After days of tries and reasearch, i don't know i managed to achive the goal. I mean i don't know exaclty which step was the key for a better illumination, but let me explain what i did and passed from this:

To this:

Explanation

1. Place the portals correctly: When using the portal function on area lamps it's important to place them the right way. They should be placed between the light emitter and the hole in the wall, not inside the room.

Like this:

2. Use a good HDRI: Use the filter "Top download" to search a good HDRI image with 22 or more EV. I set the strength of my HDRI to 40

3. Adjust exposition to you desired value: In Blender go to "Render Properties" > "Color Managment"

4. Set "Filmic" in View Transform and "High to Medium Contrast" in look: You can find this parameters in the same tab of poit .4

5. I used only transparent shader for windows but i'll make soe experiments mixing it with glass.

6. Raise a bit the "Max bounce" settings:

7. I set my render sampling to 1024, i have a little noise but for the final render i'll cranck it to 4096. Rendering time 5mins more or less.

If i forgot something I'll update this answer. Please leave you opinions, and let me know if you need the .blend file.

Thanks to the whole community and especially to @Gordon Brinkmann and @Emir that dedicated his time to my problem

Answer 2

A few other interesting things in addition to your own answer:

Ray-filtered Glass Shader

Set your windows' glass shader to be fully transparent for all rays except shadows and reflections. (example)

If you use a Glass shader:

If you use the Principled Shader (not 100% sure of the accuracy on this one, would love an expert's word on it):

Comparison:

Clamping

By default, Blender have its Direct Light Clamping disabled (zero) which is often optimal, but its Indirect Light Clamping is set to 10. Increasing this value or disabling it (set to zero) helps light entering the scene, at the cost of noise and fireflies (but a good denoising usually does the trick for that).