Deborah R. Fowler
Houdini Lighting - Mantra and Instanced Lights
Posted Dec 12 2017
Updated Feb 11 2022
You can also instance lights in Redshift
and Karma.
TIP: Remember that with real lights you
have to enable and disable them - instancing is somewhat
different - you will be disabling your instanced light by the
node display flag.
TIP: Use instance containers for your instanced geometry
(not converted geos) when using instanced lights.
Instance container node
In Houdini,
instanced lights are fun and easy to create! Think fireflies, street
lights, lanterns ...Create an instance container and in the Instance tab select
Point Instancing: Full point instancing
Instance Object: /obj/hlight1 (or whatever light you want to instance)
Light node
In your light
node, after you have the settings you want, turn off EnableResult
In the image
show, the attenuation for a point light was also adjustedYou can use any light type for instancing, except distant/sun (which would not make sense)
Hipnc here MantraInstancedLightsBasics.hipnc (H19)
Vary Lights
If
you wish to use more than one light type you can define an attribute
using an Attribute Create nodeAttribute Name: instance
Value is a String that pattern matches in this case to hlight1 and hlight2
/obj/hlight`round ( fit01 ( rand( $PT ),1 ,2 ) )`
Result
A white point
lights and a magenta cone light were instanced on a circle with 36
pointsHipnc here MantraInstancedLightsVary.hipnc (H19)
Material Override
You
can also override the properties of the lights individually by
adding a material overrideFor this to work, go into the shop network and create an ASADlight shader from the tab menu.
Add a material node with Point Attributes to your network in the instance container
(NOTE: In H19.0.383 you will want to use the render only flag - see below)
Vary Types
The results
you see below is from changing the lightcolor per pointHowever, this does not account for the other attributes that are not being used on the light shader.
A few more attribute overrides are required.
Additional Overrides - the material override on the light shader worked robustly in 18.5.532 and previous. In H19 a work around allows you to still use this method. See hipnc below.
lightcolor, doattenramp, rampend, coneangle and an expression to
"docone"The expression for docone is based on which light is being used:
if ( round( fit01( rand($PT), 1 ,2 ) ) == 1, 0, 1 )
The use of the display and render flags resolves the issues seen in H19.
Result
Hipnc file MantraInstancedLightsColorfulH19.hipnc