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Is Lightmass Importance Volume no longer needed?

I'm using UE 4.6 preview and created a small level for testing. Built the level and, to my surprise, global illumination, lighting samples grid, and apparently everything that required an Importance Volume was there. But the level had no importance volume. I didn't even get a warning.

Is the Lightmass importance volume no longer necessary? How does it determines the importance area?

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asked Nov 21 '14 at 08:14 PM in Rendering

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Hey lxiguis -

Sorry for the delay getting back with you. LIV are still important to add to a level though the error message has been reduced significantly from UDK days. The error will still pop up if you have a particularly large level with multiple elements generating Indirect Lighting. More importantly through, the LIV allows you to selectively choose where in the level you want to focus the light calculations. Those mountains that only show up in the distance, for instance, do not need to be placed inside of a LIV but without one, the engine will try to trace indirect lighting to the bounds of the level which will increase lightmap sizes and build times.

Thank You

Eric Ketchum

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answered Nov 24 '14 at 08:35 PM

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Lovecraft_K ♦♦ STAFF
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avatar image Ixiguis Nov 24 '14 at 08:38 PM

I see, thanks for the clarification Eric!

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Hey lxiguis-

The lightmass importance volume is always good to have in areas where the player will go. Though, as you pointed out, you can get lighting effects without it, anywhere that does have the importance volume will have better visuals for lighting and shadows.


Doug Wilson

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answered Nov 21 '14 at 10:13 PM

avatar image Ixiguis Nov 21 '14 at 10:29 PM

Hi Doug,

Thing is, I tried building a level both with and without a Lightmass importance volume (LIV), and couldn't notice any difference! In the past, if you hadn't placed a LIV, you would get no indirect lighting, for example. As well, you'd get a warning that you hadn't placed a LIV.

It seems that in 4.6 a LIV is automatically created internally if you don't place one. I just wanted to confirm because I'm going to give a class on UE4 tomorrow, and would be nice to know the answer.

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