Plane Contrails

This tutorial shows you how to work with Contrails in Houdini.

Overview

V-Ray Sun and Sky’s procedural clouds system provides settings to simulate plane contrails in the sky. This tutorial shows you how to control these settings to achieve the most realistic contrails.

Check the V-Ray Procedural Clouds tutorial for more details on how to build your clouds system.

To download scene files: Download Scene Files

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Workflow

Create a V-Ray Sun light from ||obj Network|| > V-Ray Sun Light.
Place the light in the viewport as you deem fit. In this tutorial, the light is in front of the VRayPhysical camera.

Note that the visibility of the contrails depends to a large extent on the camera angle and field of view, as well as on how the Sun is positioned. If the contrails are not visible after tweaking the Offset Longitude and Latitude parameters, try repositioning the camera and sun.

Let’s create the sky to complete the Sun and Sky system. For the purpose of this tutorial, use a sky texture with a VRay Environment node.

Create a V-Ray Environment node from ||out Network|| > V-Ray > V-Ray Environment.
Inside, create a V-Ray TexSky node and connect it to the Background, GI, Reflection, and Refraction ports of the environment settings node.
Connect the V-Ray Environment node to the Renderer ROP’s Environment slot.

Now set the V-Ray Sun light parameters.

Set the Sky mode to PRG Clear Sky.
Keep the rest of the main options at their default values.
Turn the Enable Clouds option on.

To achieve a cloudy sky, tweak the clouds density, variety, seed, cirrus, longitude, height, and thickness. For a clear sky, lower the Cirrus amount to 0. In this particular case, the Cirrus is set to 0.278 for a clearer sky that has occasional clouds here and there.

Let's create the contrails now.

Click the Enable Contrails option from the V-Ray Sun lights parameters.
If the contrails are not visible, set the Offset Longitude and Offset Latitude. Here, the values are set to 6.73 and 1.62 respectively.
Experiment with Number of Contrails, Strength, and Distortion to achieve the best contrails look you need.