Polymesh objects can be rendered as volumes. This gives many creative opportunities for rendering solid objects in varied and interesting ways. This short 'making of' tutorial shows how to combine a polymesh with a volume by combining their shading using the displacement attribute of a Standard Volume shader. We will also cover how to reproduce the above-animated effect using the Cell Noise, Color Correct, Ramp and Range shaders connected to volume displacement of the Standard Volume shader. An example of a free to use head scan model can be found here.
The polymesh should be closed and not have anything self-intersecting, otherwise, the volume may not render correctly.
Step Size
- First of all, we need to convert the head mesh to a volume. Select the mesh and under its Arnold attributes, increase the Step Size to 0.1. When the Step Size is positive, it turns a polymesh into a volume and its value is used as the base step for raymarching the volume.
More information about volume Step Size can be found here.
Standard Volume
- Assign a Standard Volume shader to the polymesh and increase the Density to a very high value of around 4000. This will ensure that the displacement texturing looks more defined later.
Head mesh rendered as volume
Range
- Connect a Range shader to the volume displacement of the Standard Volume shader.
- Increase its Output Max value to around 30. This will increase the effect of the volume displacement once we connect the Cell Noise shader to it.
Camera Projection
To animate the effect from top to bottom we will project a ramp through the V direction.
Create a Camera Projection shader and connect it to the Input of the Range shader.
Remember to select the render camera that you want to use for the Camera Projection.
Ramp RGB
- Create a Ramp RGB shader and connect it to the Projection Color of the Camera Projection shader.
Color Correct
- Connect a Color Correct shader and connect it to the Input of the Ramp RGB shader. You can use this to fine-tune the Cell Noise shading effect.
Cell Noise
- Create a Cell Noise shader.
- Change the Pattern to cell1.
- Disable Additive.
- Ensure that the Coord Space is set to object.
- You will need to adjust the Scale according to your scene size. In this case, the cell noise is thinner because Y and Z are less than X.
- Increase the Density to 1 and set Randomness to around 0.2 to add some irregular shapes.
Final Cell Noise settings
Animation
- Keyframe the black color of the Ramp RGB from left to right over time to see the effect move bottom to top across the head volume.
- Keyframe the Time attribute of the Cell Noise shader to animate the Cell Noise effect.
Conclusion
That's it. Remember to increase the volume samples for any lights in the scene when rendering the final animation.
Further example with Cell Noise scaled in Y