_{Depth, dust, and P Position}

This tutorial shows how to create Z Depth, dust, and Object Position masks that can be used in a compositing package to layer shading effects such as depth of field, dirt, dust, or snow. They use a combination of Arnold shaders such as utility, range, and state_float. Thanks to Slava Sych for the assistance with this tutorial.

A scene file can be found here.

Depth Mask

• Create a state_float shader. Set the variable parameter to ray_length (Rl).

• Create a range shader and connect the state_float shader output to the input of the range shader. Change the following parameters of the range shader:

• • input_min: 0.6 (this value depends on the distance from the camera your object is).
• • output_max: 1.5 (this value depends on the distance from the camera your object is).
• • smoothstep : Enabled

Note: Note that this mask directly depends on the distance from the camera.

Object Position (n) Dust Mask

• Create a utility shader. Set the following parameters for the utility shader:

• • color_mode: normal (n)
• • shade_mode: flat

• Create a range shader and connect the utility shaders Output.G to the input of the range shader. Enable smoothstep and control the mask position with the input_min/max parameters.

If you cannot connect a single out color (Out G) to an Input in your DCC, use a rgba_to_float (mode G) shader to convert it.

Object Position (P) Mask

• Create a utility shader. Set the following parameters for the utility shader:

• • color_mode: shading point (P)
• • shade_mode: Flat

• Create a range shader and connect the utility shaders Output.G to the Input of the Range shader. Enable smoothstep and control the mask position with the input_min/max parameters.

If you cannot connect a single out color (Out G) to an Input in your DCC, use a rgba_to_float (mode G) shader to convert it.