Is there a way to access the subdivision tool for radiosity Blender used to have many years ago in the latest Blender?
That subdivision tool can be used as modeling tool that can subdivide a mesh as many times as you want and you retain your uvs?
Currently, you can keep an original mesh with correct UVs, subdivide a copy as you want with the tool you want to use, and then do a data transfer of UVs.
In future, you should be able to use a Dyntopo preserving UVs.
Radiosity subdivision was replacing mesh by another one with color stored in Vertex Color channels.
If I recall correctly the process ; I think you had to recreate UVs after new mesh generation to be able to map textures.
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i have never heard about it either, seems like he refers to this https://docs.blender.org/api/htmlI/x8932.html but it must no longer supported, or it is now called adaptive subdivision idk?
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Oh, I’ve heard of it. I’ve used it. It was the only way to calculate soft(ish) bounce lighting before Cycles. Definitely a very old, very bonky technique, but it worked. It made your scenes look like they came right out of UT’99, but it worked!
It was essentially a GI renderer, but at the geometry level, as it baked all of the lighting data into vertex colors. It needed a form of adaptive subdivision to simplify the calculations while still allowing for some degree of shading fidelity. Check it out in action, you can see the emitting faces being sampled against the receiving faces in real time.
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Yeah, is there a way to access that adaptive subdivision feature in Blender 4.2? 3dsmax I think had this as a subdivide modifier. I think it didn’t destory your uvs after using it in 3dsmax. So it should be the same in Blender. Funny how 3dsmax kept that radiosity subdviding feature for modeling but Blender removed theirs.
If that’s the case, never mind. Blender needs a way to subdivide a mesh adaptively like 3dsmax and you keep your uvs after subdividing. Uv mapping a subdivided mesh that is high poly isn’t performance friendly.
I tried that in 4.2, it didn’t work. The Uvs transferred but the textures appeared incorrectly on the subdivided mesh in the viewport.
I believe all the code that the radiosity tool used is looong gone.
4.2 is an alpha. You may have encounter a bug. You should try with 4.1 or 3.6LTS.
Radiosity tools were removed when Blender Internal, obtained Indirect lighting in 2.5.
Indirect lighting of 2.5 completely losts its interest ; when Cycles became available in an official release.
Nowadays, BI code that survived 2.8 transition is restricted to old textures and Freestyle.
Adaptive Subdivision of Subdivision Surface modifier is currently a micro-displacement Cycles feature, hidden behind Experimental tag.
It does not mess up UVs. But it is only done at render process.
Maybe I don’t understand your question, but you can currently subdivide a mesh however you want (manually, with subdiv or multires modifier, via experimental microdisplacement) and still keep your UV’s untouched.
Here’s a cube with default UVs, one copy has a subdiv modifier applied, the other has a couple of manual subdivisions on some faces, and the resulting mesh still has the original UVs intact:
Is that what you need? The old radiosity feature doesn’t sound like it would be useful at all now…
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Im also doesnt really understand the question and what is your final goal?
I didnt know how those kind of subdivision works in older blender versions, but i remember how it was in 3ds max. My thougth is that 3ds max radiosity subd based on direct lighting. Theres no such things in newest blender versions, but its (probably) can be replicated by geonodes.
What is your final goal? Why you even ned this? For vertex baked lghting, no?
Radiosity seems difficult to use for modeling. 
Try it yourself. Blender 2.49b (I don’t know if the higher version has the Radiosity feature)
blender 2.49b download → https://download.blender.org/release/Blender2.49b/
Add…
Object tested for radiosity on blender 2.49b (scene configuration like the video attached above)
I don’t know what the benefits are.
※ Since this method is a kind of simulation, there may be scenes that are not controlled in the way you want and require significant computation.
That’s already the answer… it’s not used anymore… so i can’t be accessed… because it isn’t existent in modern blender versions.