Deborah R. Fowler

Houdini Tips and Tricks — Lighting and Rendering

Posted 2013 Updated Feb 17 2026 Updated Apr 26 2026 — restyled

Files created by Deborah R. Fowler unless otherwise noted.

H21: TOPS (task operators) — example if you are running low on RAM or need to write out smaller USD files for a sim:

Example File testTopUsd.hipnc

Note with particles: if you are using "spheres" there is no need to copy geometry — Karma (like Mantra and Redshift) renders points as spheres with the proper setup.

Python Script for HUSK single frame — you can also run this command line with the python script:

Example File huskTops.py

Example File points.hipnc

H21: Tiled renders and Karma — another TOPS example:

Example File tiled.zip

Contains a hip file to do tiled rendering in Karma both from the GUI (USD render ROP, nearly identical to the Mantra example at the bottom of the page), using USD ROP with HUSK, and — most importantly — with some Python help to make USD work on the renderfarm (intended for single-frame tiling).

This page is populated with Redshift tips as well as general tips. More Karma-specific information can also be seen on my overview page — as I restyle my website I will be working on including them here as well.

Tips

If in Mantra — PBR! Now use Karma.
If you are rendering water, metal, or anything reflective, make sure you have something to reflect. The env light (dome in Redshift) is a very handy method of adding an environment. Troubleshooting tip: black parts of water, dull-looking metal.
H18 and up: Solaris has a light mixer and light linker — similar capabilities to the former data tree from Mantra/obj.
Note in H21: the X button for light linker and material linker does not show up on float, but you can still delete a material by clicking in the same space. This screenshot is from 20.5:
In Mantra, every object container had masks for refractions/reflections etc. which can come in handy (this is true for Redshift as well — look under the Trace Sets tab). In Karma this is now handled with a geometry property.
Example File testbake2.hipnc
Simple Baker — promote attribute of Cd to vertex after paint and apply simple baker.
NOTE: To get the SideFX Labs shelf tools, select them from Extra Shelf Tools, update, then restart Houdini.
Fog — odforce forum thread — also see the example below.
God Rays and Volumetric Lighting

Ignore posts about the atmosphere node and shop shader (deprecated). Moving forward you can use similar techniques in Mantra — use the volume shader with a directional light and make sure you check Enable Lighting and add it to the Volume group on the light node.

In Redshift, go to your ROP node and under Redshift / Advanced / Volume Scatter, click Enable for Volume Scatter. As long as your light has a Contribution value for Volume you will get the god ray (defaults to 1; set to 0 for lights you don't want to contribute). In the sample file it is set to 2 just to show the controls.

When rendering volumes, to create a Redshift volumetric shader: create an RS Material Builder, delete the surface shader, tab-create an RS Volume, plug it into Volume — done.
Motion Blur
- Mantra — check Allow Motion Blur in the Mantra node. Also change your geometry object to have Geometry Velocity Blur on. To add motion_vector as an extra image plane, modify the shader on your object to include this information using the VOP node getblurP and turn off Allow Image Motion Blur.
- Karma — follows the same principles as Mantra.
- Redshift — see section here.
- NOTE: if using velocity blur you can control the amount of blur — see motion blur on the troubleshooting page.
Quality and Speed (Mantra) — SideFX docs
Rendering using Takes — useful, but be mindful of which take you are in.
Example File blurReflections.hipnc
Reflections — how to blur in Mantra
Example File nullForCameraRotate.hipnc
Rotating a Camera — wire it to a null node and rotate the null instead.
Example File bulletColorOverrideRS.hiplc

Color Variation — Redshift with bullet solver
Example File TextureOverrideH19.zip (Mantra)

Example File TextureOverrideH19Redshift.zip (H19.5)

Texture Override — hipnc and sample textures with variation.

The key with texture overrides in Redshift is to ensure you have the correct settings on your geo (obj) container.

Also at youtube.com — Texture Override walkthrough.

Textures

Example File gridImage.hipnc
Textures — brief introduction to simple UV-ing.
Example File usingGroupForCubeFaces.hipnc
Textures — using groups to UV separate faces.
- Grouping is an extremely versatile method.
- Tip: Use a single material node with multiple groups.
Example File exampleLayeredTextureH17.hipnc
Layered Textures (layered materials with UV bind) — network view here.
Example File TiledRender.zip

Tiled Render — instructions for use on the renderfarm for tiling a still image (Mantra — no easy equivalent in Redshift; read Toadstorm's blog). For Karma see top of page.