sun light vs. directional light

[gotobigo]

Hi all,
I always asked myself what is the difference between a sun light and a directional light. Is there any difference?
It seems that I can't set a directional light as the sun light source for the GI or the Background which is a pity cause the sun angle calculator is pretty unusable.

Since that sun angle calculator dialog is a RDK issue I posted my wishes about it on the Rhino newsgroup (http://news2.mcneel.com/scripts/dnew...m=287619&utag=)

thx
Tobias

[Micha_cg]

Re: sun light vs. directional light

Biggest difference for me - dir light create highlights (faked reflections) and the sun light create reflections. The extrem bright sun light reflection can cause noise artefacts at blury reflections. Highlights are shown at the first "reflection" bounce only, interreflection artefacts are inpossible.

An advantage of the sun light is, that the light color is dependent from the light angle - flat angle cause an evening mood ...

[dalomar_cg]

Re: sun light vs. directional light

There is quite a big difference between the two. A direct light is just a normal light (color/intensity) that emits its light w parallel rays from an "infinite" distance. A vray sun has the same parallel ray, infinite distance thing, but it doesn't get controlled like a normal light, and it interacts more with the rest of the scene. The goal of the vray sun is to be part of a physically-based system for simulating the sun and sky. So the settings in the sun control the color of the light (ozone...only within a certain range), the color/affect of the sky (turbidity...again only with a range), and also derives its intensity from the real world levels. On top of the difference in the control of the light, those values will exhibit themselves differently based on the actual position of the sun. Therefore, the appearance of the system changes from 12noon to 6pm, which is good for simulating the changing sun conditions of the day.