Lightmap build for selected objects only.


I am not sure if this has been mentioned already but rebuilding the lights over and over again for just moving a light or changing a small settings in lights, blueprints takes a lot of time even in preview mode.
It seams right now the only option is to build the entire level lights. It will be nice if we can have the option to build for lights by selected only like it was in previous engines, UDK for example. It save us a lot of waiting time.

It seams many people already ask this question on unreal hub:

But I couldn’t find a feature request for it.

Thank you for your time.

Hi Tendogames,

This feature has long been requested and has been logged here: Unreal Engine Issues and Bug Tracker (UE-10034)

I’m not aware of any immediate plans to implement this feature, though.

One solution, to alleviate the impact of lightmap building, would be to split the level into several ones.
As lighting is built per level, you could only then build the part where you are working in.
Later when the lighting pans out as desired, recombine the levels.

Hi, I wanted to bring this back as I can’t seem to find any updated information on this topic. The feature request link seems to be dead (Unreal Engine Issues and Bug Tracker (UE-10034)) Does that mean there is no intention of ever implementing this change?

I’m writing this as I wait for my entire scene to rebuild over the course of several hours, because I accidentally clicked on a light map resolution tick box for one mesh after my light build. It would be very beneficial to recalculate the light bake on only the selected object, even if it doesn’t do it as accurately as when you build the entire scene together in order to save time when you’re up against a deadline.

Can you please consider implementing this change? It’s invaluable for arch-viz professionals. It’s the reason region renders, and object selection renders were implemented in V-ray and other render engines. Speed is king in this industry, and is the reason why V-ray is so successful (in my opinion). It has the flexibility to provide quick results (using irradiance map and region renders for revisions) as well as high-end photo realistic results at the cost of render time (doing a full re-render with a super low noise thresholds using brute force). Thank you.

1 Like

its kinda sad this is gone though, saved me loads of time back in ut2k4 :stuck_out_tongue:


This has often been a requested feature and the ticket is still in our system but is backlogged. It’s not something that is likely to happen though (at least not in the foreseeable future that I’m aware of). One key point that is mentioned in the ticket’s description is that if it were to be implemented it’s not going to be as fast as everyone expects it to be and it would require a lot of global setup work to make it happen.

V-Ray for Unreal 4 will be released eventually.

Vray has a better method for rendering, but would have to contend with the same things that lightmass would, baking lighting is different from rendering an image.

Not really. In path tracing you start bunch rays from camera and intersect with geometry and then send bunch of rays from intersect points. In lightmap rendering you would just start rays from lightmap texels and only care about diffuse rays. It’s just texture space lighting instead of screenspace lighting.

The speed improvement to bake lighting for one object isn’t comparable to reducing the amount of pixels you’re rendering in a camera view. There’s a lot of stuff that it has to do that wastes time just to bake the lighting for that one object.

Are you sure this is how it works? I read a while ago that lightmass uses photon mapping, so even if you only wanted a lightmap for one object you would still have to do half the work for a whole scene.

Yes Lightmass uses photon mapping. But single lightmap could be updated with Vray. Lightmaps are usually lot smaller than full hd screen. It would be quite fast to bake just single object.

Hello, I created a new post without seen this one, so I duplicate my issue here :

So during in production it was a very useful tool (Build selected). We are a couple of artists in middle/big studios talking about this issue between us, and it look like to be a true lost from UE3

It’s 2021 and I would still like the Build Selected feature. I know that UE 4.26 has GPU Lightmass, but I haven’t done much testing with it and sadly don’t think it would be as fast/useful as only fixing unbuilt objects.