Set render engines to Prim Light Cache / Sec Light Cache impossible?

[fabrice_barbey]

Hi all
Is it possible to use the render engines set to Prim Light Cache / Sec Light Cache ?

Because I put a teapot on a plane and...I get very weird result :
everything is facetted and pixelized, shadow catcher do catch the shadow, black spots everywhere...

What am I missing here?

(Vray (not GPU) 6 2.1 + Max 2025)

[vladimir_krastev]

Hi, thanks for posting.

Is it possible to use the render engines set to Prim Light Cache / Sec Light Cache ?

I am not sure what you mean with this. Here in the example below the LightCache/LightCache image renders a lot faster but it does not look that good.

Could you share more details about your setup? If you could send us a scene this will be perfect.

[fabrice_barbey]

Hi Vladimir,
it's very simple:
A box, a teapot, a domelight and here is what I get (cpu or gpu)...

[vladimir_krastev]

Using Light Cache as the primary render engine can be useful in specific scenarios, but it is not commonly recommended for final production-quality renders. Light Cache is typically used as a secondary engine for calculating global illumination (GI) due to its speed and efficiency in gathering indirect lighting information. However, here are a few instances where using Light Cache as the primary GI engine might be helpful:

1. Preview Renders/Look Development

• If you're doing preview renders or look development where speed is more important than perfect accuracy, you can use Light Cache as the primary engine. It calculates lighting very quickly, so it can help with fast previews when you need to iterate rapidly.

2. Indoor Scenes with Mostly Indirect Lighting

• For interior scenes with a lot of indirect lighting, using Light Cache as a primary engine can produce acceptable results, especially when you're just trying to establish lighting setups and test rough global illumination solutions. However, for high-quality final renders, other methods like Brute Force or Irradiance Map as the primary GI engine are preferred due to their accuracy.

3. Animations with Camera Movement Only

• Light Cache can sometimes be used for animations with camera movement only, especially in situations where the lighting and environment are stable. In these cases, you can precalculate the Light Cache for the entire animation (using a fly-through mode), which speeds up the rendering of frames. Again, this is primarily for speed and may sacrifice some accuracy.

4. Simple Exterior Scenes

• For exterior scenes with predominantly direct sunlight or scenes with simple lighting setups, Light Cache as the primary engine may work efficiently. In these cases, there is usually less complex indirect light bouncing to calculate, and Light Cache can provide fast and acceptable results.

5. Pre-baking GI for Games or Real-time Engines

• Light Cache might also be used in workflows where you're baking GI for use in real-time engines (such as Unity or Unreal Engine) or for games. Since it's fast and produces reasonably smooth results, it can be helpful for pre-baking lighting for such purposes.

6. Draft Renders and Tests

• For draft renders, quick tests, or concept renders, where time is a constraint and accuracy is not crucial, using Light Cache as a primary GI engine can help you meet deadlines quickly and provide a general sense of lighting without being too precise.

Why It Is Not Recommended for Final Renders:

• Light Cache is a biased GI solution, which means it can sometimes produce less accurate lighting results, particularly when compared to Brute Force or even the Irradiance Map for primary GI. It tends to smooth out details, and in some cases, you may get blotches or artifacts in the GI solution.
• For final-quality rendering, where lighting accuracy and subtle detail are important, it's usually better to rely on Brute Force or Irradiance Map for the primary GI and use Light Cache as the secondary GI engine for faster calculation of indirect light bounces.

Use Light Cache as a primary GI engine when:

• You need fast previews or test renders.
• You're working on interior scenes with lots of indirect light during early stages.
• You're animating scenes with camera movement only (use fly-through mode).
• You have a simple exterior scene with less complex lighting.
• You're pre-baking GI for real-time or game engines.

For most production renders, Light Cache should remain a secondary engine, with Brute Force taking the role of the primary GI engine for better accuracy and detail.

[fabrice_barbey]

Ok thanks for this complete answer Vladimir