Light object

Whether or not this object is displayed. Turn on the checkbox to have Houdini use this parameter, then set the value to 0 to hide the object, or 1 to show the object. If the checkbox is off, Houdini ignores the value.

Caches object transforms once Houdini calculates them. This is especially useful for objects whose world space position is expensive to calculate (such as Sticky objects), and objects at the end of long parenting chains (such as Bones). This option is turned on by default for Sticky and Bone objects.

See the OBJ Caching section of the Houdini Preferences window for how to control the size of the object transform cache.

Object is capable of being picked in viewport.

Script to run when the object is picked in the viewport. See select scripts .

Object to point to. Constrains an object so its -Z axis always points at another object’s origin.

When specifying a look at, it is possible to specify an up vector for the look at. This controls the roll of this object when looking at the look at object.

A reference to the curve node or object you want this object to follow.

The orientation of the object around the path.

The position of the object along the path. 0.0 means at the beginning of the path, and 1.0 means the end. The integer portion of the position is used as the primitive number inside the geometry while the fractional part indicates the u value on the primitive.

If the primitive number does not exist, then it is wrapped back to the beginning. So for numbers greater than 1.0 in a path object that only have a single primitive, it wraps around to the beginning again. You can easily animate something moving around a circular track simply by continuously increasing the position value.

Keyframe this value to animate the object moving along the path.

The Parameterization option controls how position values between 0 and 1 correspond to knots on the path curve.

Controls how the Position parameter is translated into a point on the path curve. Use Arc-length (the default) to interpolate the position values evenly along the physical length of the curve.

Use Uniform to distribute the position values between the knots of the curve. This lets you slow down the object at certain points by bunching up knots in the path curve. However, it is much more convenient to simply edit the animation curve to control the speed of the object along the path.

Orient the object according to the path’s curvature.

The direction vector of the object’s Y axis to orient with.

Controls automatic banking of the object as it turns corners. Set this to 0 to turn automatic banking off.

Enables spot or cone light falloff. Spot light can be applied to any light type including area lights.

When rendering shadow maps or using a projection map with a spot light, the Cone Angle will be used to define the field of view. However, to be able to get better shadows on a certain section of geometry, it is useful to be able to de-couple the field of view control. Toggling this parameter off will enable the Projection Angle or Orthographic Width parameters.

The viewing angle used for depth map generation when perspective view is used.

The size of the spotlight’s beam. Enter the number of degrees wide the spotlight’s cone should be. You can only change this parameter if you are using a cone light.

Number of degrees of penumbra for spotlights.

Shape exponent of penumbra (larger = sharper).

Specifies the image that gets projected. The viewing angle of the light will determine the area of projection.

Distance to the near clipping plane.

Distance to the far clipping plane.

This parameter sets an environment map or IES file to be used to tint illumination based on the direction in which the light is cast. Environment maps can be used with all light types including point lights.

The space to use for environment map lookups. By default, the light’s space will be used so that transforming the light source will also transform the environment map.

When Environment Space is set to Use Environment Null, this parameter can be used to configure the transform object to use for orienting the environment map.

Specifies the angle over which the environment map should be blurred.

Scales the environment map angle, relative to the light axis. Values larger than 1 will expand the map while values less than 1 will compress the map into a smaller angle. This value is especially useful with IES maps, in which case it can be used to increase or decrease the built-in cone angle without changing the map file.

The size of the area light source. It is possible to define a different light scale in the x and y directions - for example, to produce a rectangular light.

Scales the light source intensity to take into account the visible area of the light. When enabled, increasing the size of an area light will not have any effect on the total amount of illumination produced by the light source, so that the size of the light can be adjusted only to change the softness of shadows. When disabled, increasing the size of an area light will cause the total amount of illumination produced by the light to increase proportionally with area. When rendering physically correct scenes, it is often useful to disable this option and use Physically Correct attenuation since this can produce more predictable physically accurate lighting results.

Causes the light source to emit light only in the direction of the surface normal.

When rendering a single sided light, reverses the direction of emission so that it is in the reverse normal direction.

Specifies a texture map to be used to tint illumination based on the uv coordinate on the geometry.

Enables a simple edge falloff calculation to soften the edges of primitive area light types.

The percentage of the light size that should be treated as the edge of the light source for falloff calculation.

Shape exponent for edge rolloff (larger = sharper).

Reference to a geometry object to be used for Geometry area light types. The light source will take on the appearance of the referenced geometry. Normally you should turn off the display of the originating geometry object to avoid self-shadowing artifacts.

Enabling this parameter causes the transform on this light object to be ignored, which will cause the geometry to be placed in the same location in space as the original object.

Controls the field of view for depth map generation from distant light sources.

The angle for the Sun light type. Larger angles will produce blurrier shadows.

Controls how light decreases in intensity the farther you get from the light source.

        Cl = H / ( H + D )
        

        Cl = 1 / (D * D)
        

The distance from the light at which Half Distance Attenuation produces half the light intensity.

Minimum light distance to be used for attenuation of point lights and line area lights. Point light illumination on diffuse surfaces will be constant within this radius.

The radius of effect for the light source. When rendering with many light sources, reducing the active radius can speed up renders by avoiding lighting and shadowing calculations for light sources that are outside this radius.

Enables a ramp control to directly adjust the attenuation at different distances. The ramp will be multiplied by the existing light intensity without the ramp to produce the final light intensity at a given distance.

The distance that corresponds to the first entry in the attenuation ramp. Distances smaller than the ramp start distance will be clamped - that is they will share the initial value in the ramp.

The distance that corresponds to the last entry in the attenuation ramp. Distances larger than the ramp end distance will be clamped - that is they will share the final value in the ramp. You can set the final entry in the attenuation ramp to black to ensure that the light fades out past this distance.

Linear ramp of colors to be multiplied by the light intensity at given distances.

The bias when computing shadows from this light source. This is a small distance. If occluders are within this distance, they will not be considered shadowers. This is to prevent self-shadowing artifacts due to the limited resolution of depth map shadows.

Increase the bias value to obtain a nice shadow when working with a large scene. Try a shadow bias 5-10% of the scene scale to start.

Adjust the quality of lookups when evaluating standard shadow maps or blurred shadows.

A blur on the shadow map when using depth mapped shadows, specified relative to the size of a micropolygon when rendering with Micropolygon Rendering.

Controls the fraction of the shadow map image to blur when rendering.

This parameter can be used to blur the map disregarding the surface derivatives, which are taken into account but the Shadow Softness parameter.

Generate a shadow map from this light source during the next render.

The path to the shadow map.

The resolution of the shadow map. It is a good idea to keep the resolution the same in X and Y.

The number of pixel samples to be used when rendering shadow maps. This is more important when deep shadow maps (transparent shadows) are being used.

When rendering deep shadow maps, it is possible to capture motion blur in the shadow map. If motion blurred shadows are desired, it’s important to turn on Transparent Shadows.