Light Cache Question

[jackieteh]

Hello, may i want is the Store direct light option in the Light Cacha setting use for? when i should turn it on or off??
i read this from the vray starting page and have make a simple plane and put a teapot on top the plane, create a vray sphere light,
and then render 1 image with store direct light turn on, and another with store direct light turn off, but it seem like no difference in the amges

Hoping anyone could give me a clear explaination, thank you.


Regards,
Jackie

[Svetlozar Draganov]

The Store Direct Light Option is useful when you have a scenes with a lot of lights.
When this option is ON Vray will calculate Direct Illumination with Light Cache algorithm instead of sampling each light separately, the result is usually faster render times but depending on LC settings the quality of the lights could be lower but in most of the cases the difference will be unnoticeable when you have IM or BF as a first bounce engine.

Here are a few examples when this option is ON and OFF

1.Store Direct Light = ON / Only LC as a first bounce engine - compare the quality of the lights and render times with the next image.


2.Store = OFF / LC only - better quality but longer render times.


3.Store = ON / IM + LC - compare the quality of the lights and render times with the next image.


4.Store = OFF / IM + LC - same quality but longer render times.


You can see that in the first two the examples there is a big difference in both quality and render-time - this is because only LC is used for GI calculations, however in the second two examples (IM+LC) the difference in quality is unnoticeable but the render-times difference is still quite a big.

[Dariusz Makowski (Dadal)]

Svetloza is it possible to get those renders in 32 bit format to compare and test?

[Svetlozar Draganov]

Here is the scene-file store-direct-light.zip

[davision]

Late follow-up question. What if you only have one light (the sun)? Is there any disadvantage/advantage to using Store Direct Light?

[Svetlozar Draganov]

The render times will be faster even with only one light (VraySun), but the benefit won't be as much as using man lights.
The advantages/disadvantages are the same - faster render times but slightly lower quality.