Hey there,
I`m preparing a huge scene and want to use global illumination. Just imagine a city at night with many buildings and you re going to walk through streets which get .
Now I have a bunch of questions.
Is GI in a night scene (directional light intensity= 0.02) reasonable?
With baked GI (realtime; ambient intensity=0.00) the shadows and backsides of the buildings are even for a night scene unnatural dark. Even if I rise the directional intensity up to 1.00 and more. (Note: all objects and the directional light are select as static!!) Where is the issue?
Do you recommend baked GI nor realtime GI for such a large game? I guess baked is more performant?
Maybe some other ideas and tips came up in your mind?
Consider what global illumination is used for. It mimics diffuse inter-reflection of surfaces to bounce light around the space. For this to have visual meaning, you should consider that the primary light sources would need a reasonable level of intensity, enough to allow for the bounced light to be visible.
So a night scene makes this more challenging than day, simply because there’s not as much light. The materials you are using and their diffuse intensity is also a primary factor in getting good bounce. Lastly, the amount of space you are lighting is also a consideration as it takes very long to pre-compute everything unless you’ve gone through object-by-object to set custom parameters.
When I go to light a night scene this is my checklist:
Get a good lighting balance using direct & indirect sources first before you enable GI. What are the light sources in my scene, fixtures? moonlight? fire? All of these should be executed to the best of your ability to create a compelling treatment, color scheme, shadows, etc… Typically you’d have a directional light (moon), fixture lights like streetlights (spot), and ambient lighting (hdr skybox or gradient) to build a credible lighting rig.
Spend the time needed to get a good balance. Reference images are valuable for this.
Once I get that done, I’ll ask myself if I should spend the time to add GI. Many times bounced light from a solo light source can be effectively faked using a secondary spotlight at lower intensity, taking into account the angle, color change from the material and any falloff.
(Most Pixar films are staged this way, they rarely use true GI because it’s slow and unwieldy compared to controlled hand-placed bounce lights. Check out Jeremy Vickery’s work).
But if I need pure GI for any reason, I’ll first cook off a pass with very low resolution values just to see what it adds. It may require intensity adjustments of various lights to reestablish balance, so iteration speed is important. If I’m inspired by what I’m seeing and feel it’s worth it, I’ll go in and create custom parms to ensure a good balance between resolution and speed. If you don’t change time of day or direction you might be able to bake a lot of the lighting, and add light probes for dynamic objects.
I suggest you to use Emissive material + Bloom effect to simulate Night Lighting.
Then bake street direct lights using GI (you can bake emissive materials too )
Ambient Lighting :
1.Use Night City SkyBox
2. Use Skybox as ambient light source
