How to Create Fog Effect in Houdini

V-Ray offers tools for creating atmospheric effects that simulate particulate media, like fog and atmospheric dust. These effects can be confined to specific areas using geometry objects.

The tools can be used in Houdini and Solaris. In this tutorial, you'll learn the workflow in Houdini Vanilla. We've designed the scene to be simple, so you can grasp the basics quickly and easily.

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• In the |obj| network, create a geometry that should serve as a container for the fog. For example, you can create a box, and the fog will be limited inside it and have the shape of a box.
  
  
• In the |mat| network, create a V-Ray Material Builder node. Do so by right-clicking > V-Ray > Material > V-Ray Material Builder. Assign the builder node to the geometry, and then dive inside the node.
  
  
• Inside it, V-Ray Material (VRayMtl) and V-Ray Output nodes are created automatically.
  
  
• Set the Opacity of the VRayMtl to 0.

• While still inside the V-Ray Material Builder, create a V-Ray Fog Effect (V-Ray EnvironmentFog) node by right-clicking > V-Ray > Effects > V-Ray Fog Effect.
  
  
• Plug the V-Ray Fog Effect's volume output socket to the Volume input socket of the V-Ray Output node.
  
  
• Tweak the settings of the fog node to your liking. See the V-Ray Fog Effect page for more details on what the individual fog parameters control.
  
  In essence, the Color parameter determines the hue of the fog when illuminated by light sources, so increasing the value of its Color Multiplier intensifies this color, making it more vibrant.
  
  The Transparency parameter controls the color of the volumetric shadows and the tint for the objects seen through the fog. Brighter colors in Transparency make the fog more see-through, while darker colors make it denser at a distance given by the Distance parameter.
  
  The Emission parameter controls the fog emission (self-illumination) and can be used to substitute the ambient illumination inside the fog, instead of using GI.

• You can also plug a color texture to the color_tex input slot of the fog node. For example, a V-Ray Checker or a V-Ray Noise texture.

Move the slider to the left or right to see more variations.