Houdini 21.0 Solaris and Karma

Portal lights

Optimize dome lights with portals.

Portal lights are not actual light sources, but a method to optimize dome lights and speed up the render process. Dome lights encompass the entire scene and send light rays in all directions. A typical example is light that passes through a window into a room. In such a scene, most of the light rays will illuminate the outside of the room. With a portal light you can instruct Karma to consider only those rays that will actually contribute to the illumination of the room’s interior.

The analogy of portal lights with windows is very close, because portals are always rectangular, but you can define their aspect ratio. You can transform a portal like any other geometry.

The Portal Light LOP facilitates the creation of portal lights. It lets you scale and position the portals. On the Dome Light LOP, you have a Portals parameter where you add a Scene Graph Tree path to one or more portal nodes. With Houdini’s default settings, a typical path is

You can add as many portal nodes as required, but you can also assign portals to different dome lights. The portal lights can be upstream or downstream of the dome light. It’s, for example, possible to have a room with three windows and each portal is connected to a different dome light: one light is red, the other one yellow, and the third light source carries an HDR. Of course, you can also work with different intensities or shadow settings. This way you can achieve complex light patterns and illumination scenarios. If you want to add multiple portals to the Portals parameter, use a space-separated list like:

The image below shows a cube with windows. One side was completely removed to get a better view of the room’s interior. The render also shows what you get without a portal. You can see that the cube’s outside walls are evenly lit.

The next screenshot illustrates how the room looks with a single dome light that’s connected to three portals - one for each window. You can see that the outside walls are now unlit, while the interior is correctly illuminated.

The next example illustrates the scenario that is described above with three dome lights. Each light source is tied to a different portal.

Solaris and Karma

Solaris and USD

Karma

  • Karma

    Houdini’s Physically Based USD Renderer.

  • Karma XPU

    Houdini’s fast and modern XPU render engine.

  • Color management

    Learn more about OCIO, color spaces, gamma and tone mapping.

  • Render statistics

    How to view various statistics about the render process of an on-going render or rendered image.

Karma User Guide

Look Development

  • MaterialX

    Houdini has VOP node equivalents of the MaterialX shader nodes. You can build a shader network using these nodes, or import an existing MaterialX-based shader, and use them with Karma (Houdini’s USD renderer).

  • UDIM paths

    You can encode different tiles of a texture space into different texture files, each with its own resolution. You can then specify a texture filename such as kaiju.exr, and Houdini will replace the token with the specific tile address at load time.

  • Shader translation

    Describes the Solaris shading framework, including shader node translation to USD primitives.

  • Shotbuilder tools

    Multi-Shot Pipeline in a Box.

Procedurals

Supporting documents