This is a fun effects to make in UE4 and I’m happy with what I got. The flame is layers of panning noise, and the soft edge is some Fresnel trick, so it is relatively cheap.
The Soft Edge
The mesh is a simple cylinder with a tapered end. But to achieve the soft edge effects, I use a custom Fresnel function in the opacity channel. The default UE4 Fresnel node does not work perfectly because it will also soften out both end of the tapped cylinder. But with a custom Fresnel, I’m able to get soft edge only on the upper and lower edge.
Since the cylinder meshing is pointing about the x-axis, I multiply the x-component of the ‘camera ray’ vector by 0, so that the Fresnel effects does not soften the start and the end of the cylinder, since the cylinder is pointing about x-axis.
Update: I rework the effects so that the effect is now working at different orientation. You’ll need to do the fresnel trick in local space instead. First, transform the ‘camera ray’ from world space to local space, so that the local x-component of the ‘camera ray’ is neglected. Then transform it back to world space.
Heat Distortion
This was a texture of the engine with uv distortion. Since it is flat and opaque, there is no need to use refraction. Just use a panning noise to distort the uv of the texture. The heat distortion on the cylinder mesh is actual refraction.