Light Objects cast light on other objects in a scene.
Light Objects are those objects which cast light onto other objects in a scene. With the light parameters you can control the color, shadows, atmosphere and render quality of objects lit by the light. Lights can also be viewed through and used as cameras (Viewport > Camera menu).
|Keep Position When Parenting|
When the object is re-parented, maintain its current world position by changing the object’s transform parameters.
This menu contains options for manipulating the pre-transform values. The pre-transform is an internal transform that is applied prior to the regular transform parameters. This allows you to change the frame of reference for the translate, rotate, scale parameter values below without changing the overall transform.
The left menu chooses the order in which transforms are applied (for example, scale, then rotate, then translate). This can change the position and orientation of the object, in the same way that going a block and turning east takes you to a different place than turning east and then going a block.
The right menu chooses the order in which to rotate around the X, Y, and Z axes. Certain orders can make character joint transforms easier to use, depending on the character.
Translation along XYZ axes.
Degrees rotation about XYZ axes.
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.
Scales the viewport geometry. This parameter is only for display purposes.
|Cache Object Transform|
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.
|Viewport Selecting Enabled|
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
|Look At Up Vector|
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.
If the primitive number does not exist, then it is wrapped back to the beginning. So for numbers greater than
Keyframe this value to animate the object moving along the path.
The Follow Path tool on the shelf automatically sets keyframes on this parameter that you may want to edit or replace.
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 Along Path|
Orient the object according to the path’s curvature.
|Orient Up Vector|
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
The type of light. See the description of light types.
The color of the light source.
A scale on the color. If the intensity is 0, the light is disabled. The light will only be sent to the renderer if the object is included in the Force Lights parameter of the output driver.
Turning this toggle off is equivalent to setting the light intensity to 0.
|Enable Light In Viewport|
Turning this off removes the light from consideration in the viewport. This is useful for lights which only make sense at render time.
The light will contribute to diffuse illumination when illuminating a surface.
The light will provide specular highlights on the surface when illuminating a surface.
The space or comma separated list of categories to which this object belongs.
Currently not supported for per-primitive material assignment (material SOP).
The sampling quality for area light sources and sun lights. Depending on the area of the light source, more samples might be needed to provide smoother illumination. Sampling quality is specified relative to the ray sampling parameters on the mantra ROP - so if the ray samples on the ROP are set to 4 and the sampling quality is set to 4, 16 samples will be used for the light source.
|Render Light Geometry|
Causes the light source geometry to appear as an object or background in the render, as if an extra geometry object were created with the same geometry as the light source. Render light geometry can be used to identify the actual brightness of area light sources when debugging the intensity of specular highlights, and to aid in the placement of light sources in IPR renders.
Spot Light Options
Spot lights change the illumination of a light source based on the angle with the light source viewing direction. In the diagram above, the area within the center ring receives full illumination. The light falls off between the inner ring (defined by the Cone angle) and the outer ring (defined by the Cone delta). The dashed line represents where illumination is half as bright as within the cone angle. The Cone rolloff parameter moves this line between the center and outer rings.
|Enable Spot Light|
Enables spot or cone light falloff. Spot light can be applied to any light type including area lights.
|Use cone angle for field of view|
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.
|Map Blur Angle|
Specifies the angle over which the environment map should be blurred.
|Map Angle Scale|
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.
Area Light Options
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.
|Normalize Light Intensity to Area|
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.
|Reverse Emission Direction|
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.
|Enable Edge Falloff|
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.
For the best performance and quality when rendering geometry area lights, evaluate your geometry against the following checklist.
|Transform Into This Object|
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.
Distant Light Options
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.
When using area light sources, it is often useful to set the attenuation type to Physically Correct as opposed to Half Distance Attenuation or No Attenuation. Area lights are often placed close to the scene, so using non-physical attenuation can produce unrealistic results.
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.
|Use Attenuation Ramp Multiplier|
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.
|Ramp Start 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.
|Ramp End Distance|
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.
|Attenuation Ramp Multiplier|
Linear ramp of colors to be multiplied by the light intensity at given distances.
A mask of objects which will be considered occluders for the light source. When ray-traced shadows are used, only these objects will be intersected by shadow rays. When depth map shadows are used, only these objects will appear in the depth map.
It is possible to use categories by adding the
A scale on how much light is blocked by occluders. By decreasing the shadow intensity, the occluders will not block all the light, allowing some illumination through.
When this option is turned on, the surface shader of occluders will be evaluated to determine the opacity. Turning this option on will cause deep shadow maps to be used when shadowing using Depth Map Shadows.
Depth Map Options
These options only apply to depth map shadows.
Deep shadows are produced by default when rendering Depth Map Shadows with Transparent Shadows enabled. Their advantage include:
Shadows of transparent objects, including volumetric objects.
Better shadow anti-aliasing.
Deep shadow maps store the opacity of any translucent objects the light ray passes through as well as the depth of the final opaque surface.
See the discussion for the Shadow Type parameter on the Shadow tab for additional information on deep shadows.
Deep shadows use significantly more disk space than plain depth maps.
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.
|Auto-generate Shadow Map|
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.
|Depth Map Motion Blur|
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.
Allows a specific shader to override the automatically generated shader for area light rendering. If you use a surface shader to shade a light source, you should verify that the shader does not compute illumination itself. Materials assigned to light sources should only emit light - not absorb light themselves.
For example, the VEX Area Light shader can be used. This is also the shader that is used by default when rendering a light without a material assigned.
This is typically -1. However, if the object is performing point instancing, then this variable will be set to the point number of the template geometry. For the IPT variable to be active, the Point Instancing parameter must be turned on in this object.
This variable is deprecated. Use the instancepoint expression function instead.
|TransparentShadows||Load | Launch|
This example shows how to configure transparent shadows with deep shadow maps. The scene includes a transparent grid which casts a shadow on the scene. The renderer used is micropolygon rendering.
|RainbowGeometryLight||Load | Launch|
This example highlights several features:
Geometry area lights
Attenuation ramp controls
Surface model specular layers
The example consists of a geometry light based on a wireframe of nurbs curves. The attenuation on the light uses colored keys, allowing for different light colors to be produced at different distances from the light. The ground plane shader uses a surface model with two specular components - one wide component and another narrower glossy component to give a multi-layered appearance.
Examples that use this node
|Example for||Example name|
|Cloth Solver||SphereClothCollision||Load | Launch|
|Gas Embed Fluid||CombinedSmoke||Load | Launch|
|Gas Up Res||UpresRetime||Load | Launch|
|Particle Fluid Object||WorkflowExample||Load | Launch|
|Particle Fluid Solver||WorkflowExample||Load | Launch|
|Pyro Solver||BillowyTurbine||Load | Launch|
|RBD Pin Constraint||Chainlinks||Load | Launch|
|Smoke Object||RestField||Load | Launch|
|Indirect Light||IndirectLightBox||Load | Launch|
|Indirect Light||TubeCaustic||Load | Launch|
|Fetch||Fetch||Load | Launch|
|Mantra||MotionVector||Load | Launch|
|Mantra||Volume Rendering - File Referenced Smoke||Load | Launch|
|Mantra||Volume Rendering - From Primitives||Load | Launch|
|Mantra||Volume Rendering - Metaballs as Volume||Load | Launch|
|RampReference||Load | Launch|
|AtmosphereShader||Load | Launch|
|Material||Down Hill Lava Flow||Load | Launch|
|TangentNormalMapExample||Load | Launch|
|Attrib Create||CurveTexturing||Load | Launch|
|Cluster Points||AnimatedSourcePoints||Load | Launch|
|Dop Import||LowHigh||Load | Launch|
|Fur||FurBallWorkflow||Load | Launch|
|Iso Offset||Brickify||Load | Launch|
|Volume Merge||volumemerge||Load | Launch|
|Ray Trace||RaytraceVopShader||Load | Launch|