Hemisphere light color mix

[donmccurdy]

@Fabrice3D

To my understanding, the color should be the average of 2 dotprods.

This is not a correct assumption for a physically-based lighting model, and in general there is no guarantee that reflected light will have the same RGB values as incoming light. Results will also depend on choices like material parameters, rendering color space, tone mapping, exposure… I’m not sure what decisions you’ve made there, or whether you’re using a framework like R3F or Threlte that has additional defaults.

There were important changes in r155, described in —

Updates to lighting in three.js r155

The upcoming release r155 will contain a major change in context of lighting. The legacy lighting mode will be disabled by default which affects all light intensities and how point and spot lights decay. What does that mean for me? The release changes the default of WebGLRenderer.useLegacyLights from true to false and also deprecates the property. Meaning it will be eventually removed from the engine with r165. Setting WebGLRenderer.useLegacyLights to false is one important prerequisite for a…

You might find the answers you’re looking for there, and in particular…

• Light intensities are not internally scaled by factor PI anymore. This so called artist-friendly light intensity scaling factor was in place to make it easier to achieve good looking lighting with intensities around 1. However, in context of physically correct lighting such scaling factors are incorrect and make it impossible to use proper SI units.

… try applying a factor of Math.PI to your intensities?

For absolute control of RGB values coming from your surface, you may prefer to use a custom shader or MatCap material.