Difference in realism / real-life physical behavior of light types

[Metin Seven]

Hi,

As the Area Light doesn't have the easy light gizmo of the other light types, I'm wondering if there are any disadvantages of using a different light type than an Area Light when it comes to realism / real-life physical light behavior?

Usually, in other renderers I've used, the area light is the only physical light type, where point lights have an unrealistic infinitely small size, causing harsh shadows and providing no reflection. But I wonder if Keyshot compensates for that with the Point Light and Spotlight parameters?

Looking at the larger radius of the Spotlight in the attached screenshots, the reflection size on the objects does not scale up along with the radius.

Thanks in advance for your help.

[DriesV]

Hi Metin,

A Spotlight with larger Radius should show up larger in reflections as well. The effect is more pronounced for Spotlights with a larger Beam Angle.
Please note that Spotlights (or IES Lights, which are all derivatives of Point Lights) can only be reflected in materials with a roughness greater than 0.

Dries

[Metin Seven]

Thanks for your reply, Dries.

I did a new test, and the spotlight area reflection is apparent now. I did notice that when comparing the spotlight to the area light, the spotlight has more noise around the reflection it casts, and there are some shadow terminator artifacts. See the attachment.

You'd expect it to be the other way round: that an area light would take more samples to get rid of noise.

Of course, the noise diminishes as time progresses, so it's not an issue, just an observation.

[DriesV]

The Radius parameter for Spotlight (or IES or Point Light) specifies the size of a virtual sphere around the center of the light. The larger the sphere, or light bulb, if you will, the softer the shadows, just like with Area Lights. That virtual sphere is not visualised in the light gizmo, but it looks like it might be intersecting with the blue sphere geometry. For lights that are positioned close to other parts, there will be more noise, if the light's radius intersects (or nearly intersects) geometry. An easy way to tell if a light is too close to an object, is when the noise is darker at the center than the surrounding area. Looking closely at the image, the seems to be the case in your test scene as well.

Dries

[Metin Seven]

Interesting. Good deduction, you're probably right.

This might also have caused the spotlight reflection issue in my first test.