Twilight Render User Forum

Lighting is a challenge in any software that is physically accurate.

In our latest release of Twilight we made a focused effort to simplify the specification of light powers. This resulted in the conversion of lights from old scenes not rendering with the same light powers as before.

We apologize for the inconvenience, but we hope that moving forward you will experience easier lighting rather than change-settings-and-guess.

Suggested light settings workflow with latest version of Twilight V2:

1. Name the light to keep scene organized
2. Set radius of light to HALF the diameter of the light bulb you would insert into the light fixture in real life. A "average" light bulb is approximately 3 inches, 8cm wide. So the radius should be 1-2 inches maximum (2 is default, but can safely be reduced to even 1/2") for metric - 5cm is default, but usually can be reduced to 1cm as a habit. Smaller radius will render more quickly. LED point lights have a radius of .01 inches, or approximately 2mm, and cast sharp shadows.
3. Attenuation: in architecture you will never change this.
4. Set efficacy based upon type of light as anticipated using the list of choices button next to "Efficacy", so if you have a light fixture with a compact fluorescent, choose "cfl" from the list, if LED, choose "LED" from the list. Then leave the power type to "Watts" and give the wattage used by the light fixture. However, if you know the specific Lumen output from your light fixture, (which an architect will know, because architects/interior designers are designing with a specific light fixture with a manufacturer who has posted this info freely and instantaneously available via the internet.) If the manufacturer provides the IES file, of course converting the light to IES and using this IES file is the best.
5. Set color of light, find the color range for the light fixture in Kelvin via the manufacturer's website:
   1. Click Color Picker (default white) and
   2. choose "RGB" tab, then click in the "K" (for Kelvin) box, and
   3. type in the numberic color of light in Kelvin temperature. (like "3500" for instance, this is an LED color chart) then click the
   4. "Convert" button to convert the K temp number into your color for your light.

For learning more about the fundamental basics of 3D lighting, check out this great tutorial:
Light - a detailed tutorial by Richard Yot ©2008

A credit for the Author Yot. to precede the tutorial please.
Wow what a complete and well presented series.

Thanks for the link

dtr

done.