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[SR] Light sources are reflected in RT even when off.

[SR] Light sources are reflected in RT even when off.

1. Question:
1.1: The light source is off. Yet, when raytraced (standard glass) they're (sources) being shown in the glass

2. Standard Reply:

See EKB article :

Why does the Light Source show in reflections?


2.1: Answer - Deprecated - covered by above EKB article:

Hi,

The light trickeries that could be done in rasterisation don't scale well with ray tracing. We've had a few reports on this topic, as from a user perspective, it would make most sense for light to be visible but for the light source not to.

However, this is an unfortunate consequence of Ray Tracing: the Reflections ( which are calculated on any object whose Roughness value is larger than 0) know that an object is emitting light, and, in order for them to be RT accurate, they will display the light source. The situation is a bit like this:

  • Reflections must either reflect all light (including light sources) or no light/light sources at all.

If the light source is hidden by a Layer or facing away from the Reflection it will be invisible always. If the light source itself is visible on diffuse surfaces then it will always be visible in reflections as well. Hiding in Build Mode itself will not hide it in the Reflections (here meaning the toggle to enable/disable the geometry of the light source).

3. Cause/Background information:

3.1: Reference:

  • https://community.lumion.com/index.php?threads/light-sources-off-but-visible-in-glass-reflection.4858/#post-22891