This is a paid asset, but now you can download Volumetric Shadows for Particles for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Volumetric Shadows for Particles v1.5
Volumetric Shadows for Particles is used to draw animated particle effects like smoke, steam, and dust with volumetric shadows for a dynamic light source. Volumetric shadows provide important visual cues that enhance realism. A modern approach to the conventional slice-based technique is used in order to achieve high performance, flexibility, and quality.
Before the particles are drawn, a volumetric shadow map is built. The particles are drawn once or twice from the view point of the light using multiple render targets. For 6 and 12 slices, the particles are drawn once. For 24 slices, the particles are drawn one addition time. The shadow map is used to draw the particles and surfaces in the scene with volumetric shadows.
Demos:
12SliceFire Windows
12SliceFireOrtho Windows
24SliceSmoke Windows
12SliceFire Mac
12SliceFireOrtho Mac
24SliceSmoke Mac
Documentation
Key Features:
-Choose between 6, 12, and 24 slices
-Choose between an orthographic directional light or a perspective spotlight
-Control the appearance and quality of volumetric shadows for particle effects
-Supports soft particles
-Supports emissive effects like fire
-Includes custom surface shading with normal mapping
-Supports Unity’s soft and hard shadows for shadowing surfaces
-Includes a solution for casting solid surface shadows on particles
-Compatible with and tested on Windows and Mac operating systems
-Compatible with Direct3D (9 and above) and OpenGL (2.1 and above)
Requires at least Shader Model 3.0
Not recommended for most mobile devices.