How do you use plants/trees in archviz projects?

I have been having some trouble lately with a scene where the character can roam outside the house as well as inside the house. The lighting has been set up and everything looks great.
I used the GPU Lightmass plugin and I am on UE4 4.23
After I finalized the materials and lighting, I started adding interior plants and trees from the megascans and free stuff from Epic. The only problem is that the bake time went up from 5-10 minutes to 17-18 hrs. So I canceled the bake and set every plant and tree to movable and still the bake time was 1-2 hrs.

How do you guys go around doing this for your archviz projects?
Do you use your own assets or third-party assets?
And do you keep them static or movable?

So I had to delete the downloaded assets folder from my project and now it is back to 5-10 mins bake time.
But still need to find a way to add plants to my scene

When I read stories like yours I wonder which tutorial or documentation people follow to end up with build times of 18 hours. There must be some advise out there I am unaware of that everyone follows without ever questioning it. I don’t want to get philosophical. But I always try to not fix things that are not broken. In your case it might not be the plants that cause your 18 hour build time, it might be some settings you changed that didn’t need changing. Imagine you set the amount of bounces to 100.000. Your scene will look good but it also looks good with 10 bounces. Probably the same as common knowledge is that after a few bounces any additional bounces don’t really do anything. It’s a thin line where quality is great without hitting build time too much.

I haven’t really used gpu lightmass because it often doesn’t work with the features I want to use. I know people are using it successfully but it is experimental still.

How many plants are in the scene? Check the lightmap sizes of those plants especially the ones you use a lot. Large light map sizes increases build times. If you also have increased your default settings this can quickly get out of hand.

I don’t think you read the OP carefully. It clearly says that I finalized the lighting and then added plants so there is no reason for anyone to change the lighting after finalizing it.
Neither the lightmaps were changed. They were pretty good and at 64,128.
To find out what would happen if I let it bake for a few minutes, I got the “Out of memory” error. Reduced the plants but again the same error. Deleted the plants but kept the grass but same error.

Anyways, I have come to the conclusion that my GPU isn’t that capable when it comes to handling some vegetation. WIll just have to upgrade when I can.

Just trying to help. To answer your question on how we place our plants:

I worked on scenes were we had something like 30.000+ trees in it. That was a few years ago. Running with a 1080 probably on maybe 20-30 fps. We placed them with the foliage tool and set them to be dynamic and only cast dynamic shadows. With static trees we would get the out of memory crashes. It was mostly fully dynamic lighting with no interior but lots of exterior buildings and meshes.

I’m currently working on a ray traced scene. A large house with 4 bath rooms, 2 stories one under ground. I modelled what can be seen from the surrounding. I placed most speed trees by hand to enable ‘evaluate world position’ so they have proper self shadowing when moving by wind. The ones further away are placed as foliage or as groups of instances. Maybe about 150 trees plus other smaller plants. LM resolution is 128. I have foliage with 18.000 grass meshes (resolution 16) on the lawn which are set to static and cast dynamic and static shadows. I have also grass on the terrain but it spawns dynamically around the player with the landscape grass tool so hard to say how many meshes. They are set to dynamic otherwise it would blow out the lightmap size and probably crash. I’m using a laptop with a 2070. Production lighting might take about 3-4 hours on the laptop. Preview takes less than an hour.

Building lighting on a swarm network with a few computers took 15 minutes in production mode apparently but I don’t have access to that locally.