4.12.5 had many different things for last time.
Are by any chance referring to unreal changing from Deferred to Forward rendering?
I do not remember state of 4.27 in that area, however unreal 5 has most of those problems fixed.
If you gave description of exact things not working anymore there may be some better reply.
Yellow Rubber Duck made summary:
| Feature / Effect | Deferred | Forward |
|---|---|---|
| Screen Space Reflections (SSR) |  |
 |
| GBuffer (World Normal, Roughness, etc.) | |
|
| Advanced Post-Process Effects | |
 Limited |
| Real-time Translucent Shadows | |
|
| Per-pixel dynamic lighting | |
Limited |
| Volumetric Fog | |
(older), (newer) |
| Material-based stylized shading tricks | |
|
state in ue 4.27:
| Feature | Status in 4.27 |
|---|---|
| Planar Reflections in Forward | More stable, usable |
| Pixel Depth Offset in Forward | Improved support |
| Custom Depth / Stencil for Outlines | More reliable |
| SSR in Forward | Still not supported |
| GBuffer Access in Forward | Not available |
| Translucent Shadows in Forward | Still broken/limited |
| Volumetric Fog | Still tied to deferred |
| Reflection Capture System | Performance + quality |
really that chatGPT while dumb at coding is great at making nice summaries:
| Feature / Effect | 4.12 Deferred | 5.5 Deferred | 5.5 Forward Rendering | Notes |
|---|---|---|---|---|
| GBuffer Access (SceneTexture) | Full |
Full |
Not available |
Forward rendering still lacks direct GBuffer, limiting advanced FX |
| SSR (Screen Space Reflections) | Good quality |
Lumen / SSR |
Not supported |
Lumen is a great SSR alt, but only works in deferred or hybrid modes |
| Translucent Shadows | Very limited |
Better in deferred |
Still limited |
Forward can fake it with tricks, but no full dynamic translucent shadowing |
| Volumetric Fog | Available |
Improved |
Still not fully supported |
Forward still lacks rich volumetric lighting/fog |
| SceneTexture in Materials | Usable |
Usable |
Not supported |
SceneTexture nodes disabled in forward — no stylized effects that rely on it |
| Custom Depth / Stencil | Supported |
Improved |
Supported |
Works across both paths, useful for outlines, silhouettes, etc. |
| Pixel Depth Offset (PDO) | Deferred only |
Deferred + Forward |
Supported (now) |
Now works in forward — useful for soft particles, stylized edges |
| TAA / Anti-Aliasing Options | TAA + FXAA |
TAA / TSR |
MSAA only (by default) |
Forward lacks TSR/TAA by default, but MSAA can be clean for VR |
| Dynamic Lighting Scalability | Limited lights |
With MegaLights |
With MegaLights (exp.) |
MegaLights in 5.5 improves light count — great step forward |
| Planar Reflections | Experimental |
Stable |
Supported |
Available in forward, though performance-heavy |
| Stylized / Postprocess-Heavy FX | Easy via GBuffer |
Best in deferred |
Very limited |
Still a major pain point in forward rendering |
| Shader Complexity View (debug) | Full metrics |
Full metrics |
Not available |
Forward rendering lacks in-depth debug views |
| Lumen Global Illumination | Not available |
Deferred only |
Not supported |
Forward rendering doesn’t support Lumen GI or reflections |
and final table:
| Lost in 4.12+ | Replaced in UE 5.5? | How? |
|---|---|---|
| SSR in forward | Not yet |
Only in deferred with Lumen |
| Full GBuffer access in forward | Still missing |
Use deferred rendering |
| Translucent shadows | Partially |
Improved in deferred, not fixed in forward |
| Postprocess stylization | Half-fixed |
CustomDepth + improved PDO, but not full scene-based FX |
| PDO in forward | Fixed |
Now works in both rendering paths |
| Light count limits | Improved |
MegaLights (experimental) lifts limits |
| Volumetric fog in forward | Still limited |
Deferred still the way to go for full volumetrics |
So after summary spam solution would be. Unreal 5.5.