Houdini Lighting — Solaris/Karma

• Cylinder — control size with radius and length
• Distant — directional light; parallel rays simulate the sun
• Disk — control radius; one-sided
• Point — calculates from a point source; cheaper, works well, good for practical lights
• Rectangle — area light; control width/height; one-sided; normalize power off by default
• Sphere — visually better than a point light

• Dome — environment light; usually use an HDRI in the texture parameter
• Spotlights — created via a checkbox under the Shaping tab
• Geometry — make your own geo a light source

All light types have both intensity and exposure controls.

• Active Radius — limit the reach of light calculations
• Sampling Quality — per-light sampling override