Rendering Foundations for Houdini and Karma

Taught by Niall Flinn

Course Number:
Software Version:
Original Run Date:
March 2021 
4 hours 36 minutes 
This course provides a comprehensive introduction to rendering in Houdini, with a focus on FX simulations, such as rigid bodies, particles and volumes. It assumes a basic familiarity with FX simulation and with the Houdini UI. There is a focus throughout the course on a balance of speed and quality which will help ensure your success in the industry.

The first few lessons walk the viewer through the very basics of rendering in Houdini; different ways of starting and monitoring renders; Houdini’s various light types (and their uses); and provides a very solid foundation in shader development, from simple constant shaders, through to volume displacement.

The course later moves into more advanced topics such as how modern path tracers work (complete with a functioning renderer built into an Attribute Wrangle SOP; rendering with physically correct motion blur (a topic rarely well understood by FX and Lighting artists) and efficient delayed load workflows.

The last few lessons walk through the specifics of rendering an example scene containing rigid bodies, particle instances and volumes, with attention given to the integration of these elements in the comp. Finally, there is a brief introduction to Houdini’s new Lighting OPerators (LOPs) and render engine, Karma.

Niall Flinn is a senior Houdini FX artist and Computer Graphics Supervisor with over 17 years experience of working on feature films and high-end television productions, with many credits to his name. He has hired, supervised, and mentored numerous artists and built FX departments at two different companies. This experience has given him an intimate familiarity with the balance of creativity and technical excellence required to succeed in today’s visual effects industry.
Rendering Foundations for Houdini and Karma
Watch our overview of the course

Class Listing

Class 1: Introduction to Rendering in Houdini

Good practices for scene organization and the creation of Render Operators. Creating lights and assigning shaders to scene geometry and finally running and viewing interactive and batch renders.

Class 2: Houdini Lights

A tour of the various different lights available for rendering in Mantra. A discussion of the parameters available to control each light type and how each light might be used, while interactively rendering an example scene.

Class 3: Shaders

How to construct a range of shaders from the ground up, starting with very basic constant and diffuse shaders, and quickly working up to more complex examples with reflection, refraction and displacement.

Class 4: Motion Blur

Motion blur is an incredibly important factor for high-quality FX rendering, but it’s rarely well understood by artists. This class is deep dive into the subject, starting with the history and theory of motion blur, and moving on to practical instruction on achieving correct motion blur in Houdini.

Class 5: How Does a Pathtracer Work?

Mantra’s PBR engine (and most modern renderers) is a path tracer and solid insight into how this type of rendering algorithm works will help FX and Lighting artists to produce high-quality images in reasonable timeframes. With this in mind, this class demonstrates the principles of path-traced rendering by running a “toy” renderer that is able to output ray geometry in the Houdini viewport for inspection.

Class 6: Delayed Load Workflows and Packed Primitives

When working on real-life TV and feature film projects, FX and Lighting artists often have to be able to render very large amounts of data efficiently. How to use Houdini’s Packed Primitives to keep IFD files small and load geometry directly from disk, using a rigid body simulation as an example.

Class 7: Particles

A practical overview of rendering particle instances, building on the information from the previous lesson.

Class 8: Volumes

This class adds a fluid sim to the example scene we’ve been building up and demonstrates practically how to balance quality and speed when rendering volumetric data in Mantra.

Class 9: AOVs, Deeps, Optimization

When working in a VFX studio, it’s important to be able to set up Arbitrary Output Variables for comp. A walk-through of Mantra ROP’s default set of AOVs and how to create additional custom ones. How to output deep data and an explanation of why this might be a good thing to do. Finally, a walk through of using frustum culling scene geometry as a way to reduce memory consumption.

Class 10: LOPs and Karma

SideFX is rapidly developing its new USD-based Lighting OPerators context and Karma, the renderer that goes with it. Karma is still beta software at the time of recording, but a Houdini rendering course would be incomplete without at least an introduction to these new tools, and that’s what this class is. We take some of the assets we’ve been working with so far and render them in LOPs.