How the transform parameters below apply to the primitive. (Because each USD prim can contain multiple transforms, and be affected by parent transforms, there are many different ways to apply new transforms.)

The order in which Houdini applies translates, rotates, and scales, and the order in which it applies rotation.

Movement amount along XYZ axes.

Degrees rotation around XYZ axes.

Non-uniform scaling along XYZ axes.

Amount of shearing. The three values represent shearing in the X direction on the XY plane, in the X direction on the XZ plane, and in the Y direction on the YZ plane, respectively.

Scales the object uniformly along all three axes.

Moves the local origin of the object.

Rotates the local origin of the object after translation.

Turns on the constraint that orients this object to look at a point or another object.

If Enable Look At is on and, this is a point in space this object will look at. If Look At Primitive is not blank, this is an offset from the centroid of the target object (in the local space of that object).

The path to a USD prim this object should look at. If this is not blank, Look At Position is an offset from this centroid of the target object.

Controls how the up vector is set.

When Up Vector Method is Custom, this is the up axis to use for the look-at constraint.

A twist rotation (around the -Z axis, clockwise, in degrees), applied after the lookout transform.

A linear scale on the power output of the light.

Scales the power output exponentially as a power of 2, similar to an F-stop control. 0 does not scale intensity, negative numbers scale intensity down by the square, positive numbers scale intensity up. Often you will set the Intensity to what looks like the right amount of light, and then use this parameter to “tweak” it.

The color of the light, in energy-linear terms.

Use Color Temperature to control the light color. The color calculated by Color Temperature is multiplied by the RGB color in Color, so if you want the “pure” temperature color, you should set Color to 1.0, 1.0, 1.0.

When Enable Color Temperature is on, the temperature (in degrees Kelvin) to simulate. The valid range is from 1000 to 10000. Lower values are warmer and higher values are cooler. The default is the common D65 white point.

If necessary, you can compute the same color value using the UsdLuxBlackbodyTemperatureAsRgb() function from the USD library.

Don’t show geometry closer than the near distance or farther away than the far distance (in world units).

Divides the set power output (intensity scaled by exposure) by the surface area or angular size of the light. This makes it easier to adjust and compare energy output without it being affected by the size of the light.

Scales the effect this light has on the diffuse response of shaders. This is a non-physical “tweak”.

Scales the effect this light has on the specular response of shaders. This is a non-physical “tweak”.

Applies a uniform scaling factor on the guide geometry that is drawn for the light in the viewport. The default value is an expression that inverts the “meters per unit” value of the USD stage to produce a consistent real-world size for the guide geometry.

Turn off this option to prevent this light from showing up in the camera menu in the viewport. This can be useful to hide lights that are embedded in props, or other lights that are not meant to be modified.

A space-separated list of light filters you want to use with the light. You can create a light filter in a Light Filter Library LOP.

File path to the texture file to use as an environment map.

How the spherical environment is encoded in the texture image. The default, Automatic, tries to guess.

Optional light filter primitives that should be applied to this light.

Optional portal geometry prim(s) to use to guide light sampling. Note that Houdini supports single-sided portal lights. Go to the __Karma_ tab’s Light section and turn on single Sided. If you're using the Portal Light LOP, add the path to the downstream portal light node(s) here.

Indicates the starting alignment of the dome light’s top pole. This alignment is for the dome itself and is not inherited by the namespace children of the dome.

When this is on, objects hit by this light will cast shadows (subject to shadow masks).

Tints the color of shadows cast by this light. Changing this from black (0, 0, 0) is a non-physical “tweak”.

The near distance at which shadow falloff begins.

The default value (-1) indicates no falloff.

A gamma (i.e., exponential) control over shadow strength with linear distance within the falloff zone (between Falloff and Distance).

The maximum distance to check for objects shadowing this light. The default is -1, meaning no limit. Setting this may speed up rendering if you know all objects you want shadowed are within a certain distance.

Controls whether multiple importance sampling will sample from the BSDF, the light, or both the BSDF and light.

This is the per-light sampling quality, that acts as a multiplier on the global Light Sampling Quality. Increasing the quality will add additional samples for this light source, improving the sampling quality of this light relative to other light sources.

When using the light tree for rendering, Karma will try to put any light source that’s compatible into the tree. This option can force a light to be excluded from the tree and subject to uniform sampling, which can sometimes yield an improved sampling quality the light at the expense of speed.

If an environment map is larger than this resolution, it will be scaled down when performing texture analysis. If the map has some very small, very bright values, this filtering may affect how sampling of the environment map is performed.

Controls whether the dome light is more likely to sample from the environment map or the portal geometry. For high-contrast HDRI with strong light sources, it may be beneficial to sample more from the environment map (set it less than 0), and for low-contrast/flat HDRI, the opposite may be true (set it greater than 0). Leave it at ß for balanced approach.

Defines a VEX shader to be used for light evaluation. If the string is empty, the value will be taken from the HOUDINI_VEX_DEFAULT_LIGHTSURFACE configuration variable.

Artificially clamp the illumination distance from the light. Outside this radius, the light will have no effect.

As point lights get closer to geometry, the attenuation equation causes the intensity of lights to go to infinity (a singularity caused by the division by the distance between the light and the surface). Increasing this value to something larger than zero creates an artificial buffer zone to prevent the light from going to infinity. If the radius is set to 1, the brightest value for the point light will be twice the intensity specified on the light. If the value is 1.4142 (sqrt(2)), the brightest value will be the intensity specified.

For distant geometry, there should be very little change in the intensity.

Does the light emit light from a single side (ie along the normal) or from both sides? This only has effect on planar area light types.

Causes the light source geometry to be visible in the render.

Causes the light source geometry to cast shadows in the render.

Custom label assigned to lights or objects for use with light path expression.

If a light exists to add new light source instead of trying to replicate lighting in the live action plate, enable this parameter so that its effect on background holdout geometry shows up in indirect bounces and its contribution to shadow holdout AOVs is omitted.

Provides detailed control over which BSDF component the light affects.

Default is true. Note that Karma only renders caustics if they are enabled on both the light and the object. This option has no effect unless you also turn on Enable Caustics on the geometry object.

Ranges between 0 to 1 and controls beam direction along the light’s normal. A value of 1 results in diffuse emission, and a value close to 0 gives parallel beams of light similar to directional light. Note that the Spread option is only supported for area lights with Type set to Rectangle or Disk.

In conjunction with Disk lights you can, for example, create focused laser beams by leaving Spread at 0.