Raytracing issues

[Suthriel]

Well, most, if not all post process effects won´t be reflected by raytracing, since they are generated after the scene is already raytraced. Most noticeable is it, if you deal with particles: GPU particles won´t be raytraced, CPU particles/mesh particles usually will be (maybe this changes with Niagara). Now i don´t know, how you generated your clouds, but if they are generated by a post process or with the help of an transparent material, you won´t get them reflected. Well, transparent materials, we have to see, what 4.26 brings for them, but all that volumetric stuff is usually post process.

Spline meshes are also not supported until now, see:

Hardware Ray Tracing Tips and Tricks

[TABLE]

		Rendering Path
		
		
		 
		 
		 
	
	
		**Deferred**
		Y
		 
	
	
		**Forward**
		N
		 
	
	
		
		Types of Lights
		
		
		 
		 
		 
	
	
		**Directional Light**
		Y
		 
	
	
		**Sky Light**
		Y
		 
	
	
		**Point Light**
		Y
		 
	
	
		**Spot Light**
		Y
		 
	
	
		**Rect Light**
		Y
		 
	
	
		
		Lighting Features
		
		
		 
		 
		 
	
	
		**Emissive Surfaces**
		Partially
		Supported for reflections on surfaces, but does not emit light or cast shadows.
	
	
		**Light Transmission**
		N
		The translucent shadow is treated as opaque, meaning no colored shadows or light transmission through the material.
	
	
		**Area Shadowing**
		Y
		 
	
	
		**IES Profiles**
		Y
		 
	
	
		**Light Functions**
		N
		 
	
	
		**Volumetric Fog**
		N
		 
	
	
		**Image Based Lighting (IBL)**
		Y
		Support for HDRI with Sky Light.
	
	
		
		Materials: Blend Mode
		
		
		 
		 
		 
	
	
		**Opaque**
		Y
		 
	
	
		**Masked**
		Y
		 
	
	
		**Translucent**
		Y
		 
	
	
		**Anisotropic**
		Y
		 
	
	
		
		Materials: Shading Model
		
		
		 
		 
		 
	
	
		**Default Lit**
		Y
		 
	
	
		**Unlit**
		Partially
		 
	
	
		**Masked**
		Partially
		Supports casting of masked shadows.
	
	
		**SubSurface and SubSurface Profile**
		Y
		 
	
	
		**Preintegrated Skin**
		Partially
		Works but the result isn't correctly raytraced. It uses the raster pipeline.
	
	
		**Clear Coat**
		Y
		UE 4.25 includes significant improvements to the Clear Coat Shading Model.
	
	
		**TwoSided Foliage**
		Y
		 
	
	
		**Hair**
		Partially
		Works but the result isn't correctly raytraced. It uses the raster pipeline.
	
	
		**Cloth**
		Partially
		Works but the result isn't correctly raytraced. It uses the raster pipeline.
	
	
		**Material Functions**
		Y
		 
	
	
		**Two-Sided**
		Y
		 
	
	
		**World Position Offset**
		Y
		Static Mesh is enabled per-Actor.
	
	
		
		Geometry Types
		
		
		 
		 
		 
	
	
		**Skeletal Mesh**
		Y
		 
	
	
		**Static Mesh**
		Y
		 
	
	
		**Geometry Cache (Alembic)**
		Y
		 
	
	
		**Landscape**
		Y
		 
	
	
		**Hierarchical Instanced Static Mesh (HISM)**
		Y
		 
	
	
		**Instanced Static Mesh (ISM)**
		Y
		 
	
	
		**Splines**
		N
		 
	
	
		**Procedural Mesh**
		Y
		This type of geometry can be expensive to render in Ray Tracing.
	
	
		**BSP Brushes**
		N
		 
	
	
		**Levels of Detail (LOD)**
		Y
		Dithered LOD transitions are not yet supported.
	
	
		
		Visual Effects (VFX)
		
		
		 
		 
		 
	
	
		**Niagara**
		Partially
		Currently supports Sprites, Ribbons, and Mesh emitters.
	
	
		**Cascade**
		N
		 
	
	
		
		Platform Support
		
		
		 
		 
		 
	
	
		**Multi-View (VR and Split-Screen)**
		Y