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View Full Version : Primitive Light Color vs. Sample Surface



Ma3rk
03-12-2019, 07:08 PM
I stummbled across this while reverse engineering a Daz asset that's misbehaving in Studio. In bringing it over to Lightwave via FBX, I'm finding a lot of "why'd they do it that way?", so still sorting some things, but 90% there. This is just one socket/globe that I'll instance into position later.

I split the original geom up such that the filament is separate & used for a Primative Light. Once positioned, etc., I set the Light color and the objects color the same & toggled the setting. The result is subtly different and I not sure why or even where else to look. I prefer the Sampled better for this but would just like to know why the difference.

Any ideas?

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MarkAH
03-13-2019, 06:14 AM
More cool stuff. I think you're going to sell me 2019...
The docs say:
The light can simply emanate from geometry or the Sample Surface option can be used to take into account the geometry's surfacing.
If you use sampled surfaces, the light color and intensity act as a multiplier for the object's luminous intensity and color surfacing.

That sounds real to me.
What happens with real light that is. Both the same color so now you have R2 + G2 + B2
If the bulb was colored pure red it would emit pure red. Like B and G are zero, and zero times anything is zero.

Tobian
03-13-2019, 06:31 AM
Yeah, it's because the sampled colour is multiplied by the light colour, as as the environment light samples the environment and multiplies it by the light colour and intensity. 'sample surface' doesn't replace the colour and intensity, it multiplies it with the light, so change the light colour, or the surface colour, not both.

If you have an asset where it's a simple solid colour, like that, you're better just sampling the geometry and adjusting the light colour and intensity to suit, as it's slower to sample the objects surface. (from testing).

Ma3rk
03-13-2019, 08:48 AM
Yeah, it's because the sampled colour is multiplied by the light colour, as as the environment light samples the environment and multiplies it by the light colour and intensity. 'sample surface' doesn't replace the colour and intensity, it multiplies it with the light, so change the light colour, or the surface colour, not both.

If you have an asset where it's a simple solid colour, like that, you're better just sampling the geometry and adjusting the light colour and intensity to suit, as it's slower to sample the objects surface. (from testing).

Ah. So they work in combo of sorts & not independantly.

RebelHill
03-13-2019, 08:57 AM
Yes... in the same way that diffuse value, and diffuse colour are kind of interchangeable...

https://www.youtube.com/watch?v=I9YONXWhMxQ

Light colour and light value are too. You can think of the light colour as a kind of intensity value with separate controls for R, G, and B if you like (which is then multiplied by the main intensity scalar).

MarkAH
03-13-2019, 01:50 PM
It's all getting so nicely scientific.
You know, those newer incandescent bulbs are generating light with tungsten.
But they also have a phosphorescent coating that generates light when excited by the energy from the tungsten filament.
So you would start with the color temperature of tungsten and make the surface the color of whatever coating is used.
There's different ones you could choose, like soft white etc.
In that case just make the glass polys the tungsten primitive light with the phosphorescent surface color.
And then you'd have the most realistic lightbulb in virtual space.

Now it's LED lights and you have to get the color temperature of the LED, and I think they still have a phosphorescent coating.
I like the daylight ones. So I could have the most realistic LED daylight bulbs in my own virtual space.
Yeay! I'm almost ready to go for it.

Wade
03-13-2019, 02:36 PM
Very nice - I look forward to seeing the finished piece. Please do share when done.