Using a lot of light power

Raylectron (https://Raylectron.com) is a 3D rendering engine for Trimble Sketchup (https://sketchup.com)
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stevo1
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Using a lot of light power

Post by stevo1 »

Hi, I am using stupid amounts of lighr emitter power on this scene, Can you please tell me what I am doing wrong?
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Re: Using a lot of light power

Post by Support »

Hi, you are not doing anything wrong, the power isn't in watts or lux or candle power etc, let me explain how it works...

In v3 and earlier versions, the power was set to 35 and that's all that was used to calculate the intensity on surfaces. That worked fine for real life size models but if you scaled your model 1000x for example, nothing got lite, everything was black. Many were making models not considering the scale, so some were making a house where the height of the ceilings were 1000x higher than real life. So we fixed that by multiplying the light power with the light area, so if you scale your model 1000x, the light area will obviously by 1000x as well, so that produced the proper illumination for both scenarios.

In v5, light powers is always 1, for the sly, for the sun, for artificial lights etc. So when it is multiplied by the emitter area, it's not too bright, you can observe this with portals, the sky intensity is 1 but multiply this with the portal area and it illuminated properly. Now, your light emitters are small compared to a portal, so its power will need to be a lot higher than 1.

So if you want to illuminate the floor at a normal intensity of 1, using your emitter, we get...

Emitter Power (10631) divided by 35 for compatibility with older versions which leaves you with 303 for power. Your emitter area is 6959 square millimeters, internally converted to 10.7 square inches. The new power is 3250 (303*10.7). Now the distance from the light to the floor, say 8 foot (2438 mm) celling that's converted into inches is 96. The law of physics for a light loses it's power at a rate of one over its distance squared, so the final intensity on the floor would be power/distance^2 which is 3250/(96*96) which equal to 0.35, or 1/3 of the normal intensity of 1. Now, if you set your emitter power to 30000 you will get 1 as the intensity on the floor, which will be nice. However, the wall close to the light will be super bright, say the wall is 2 feet (610mm) away, then we have 24 inches away, so 30000/35*10.7 = 9171 and divide that by the distance squared 9171/(24*24) and you get 16 not 1, as the illumination on the wall.

That's why we have an Auto Set Values which tries to find the best combination of power and area by calculating averages of what the emitter illuminates. To get rid of these super bright spots, you just need to increase the area and lower the power. Internally, a power of 35 is 1, 35 divided by 35 for backward compatibility, that's why it's not set to 1 like the sun/sky/env.

So in short, convert everything to inches and use this formula (p*a)/(d*d) to find out if your illumination at a specific point is too low or too high, where "p" is your emitter power divided by 35 and "a" is the emitter total area + area adjustment in square inches and "d" is the distance in inches from the emitter to the illuminated point. If you get a result of 1 to 2 it should be good.

I hope all this make any sense!
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stevo1
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Re: Using a lot of light power

Post by stevo1 »

Thank you support however not many people on the planet use inches any more FYI. I had great problems with inches when I would do grass etc :) Could you have metric and imperial versions? People im metric Countries (Vast Majotity) are wondering how many inches in a cubit? :) :)
stevo1
Posts: 122
Joined: Sun May 20, 2012 4:28 am

Re: Using a lot of light power

Post by stevo1 »

One more question please. What settings should I use to make the glass better?
stevo1
Posts: 122
Joined: Sun May 20, 2012 4:28 am

Re: Using a lot of light power

Post by stevo1 »

I have it all sorted, I think this will be a cracking render :D Will post the results only 3 samples ATM.
stevo1
Posts: 122
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Re: Using a lot of light power

Post by stevo1 »

Hi I am getting these white spots (reflections from the cieling lights) as per the arrows I am only at70 passes ATM will they turn into accurate reflections eventually?
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Re: Using a lot of light power

Post by Support »

stevo1 wrote: Thu Jun 09, 2022 3:05 am Thank you support however not many people on the planet use inches any more FYI. I had great problems with inches when I would do grass etc :) Could you have metric and imperial versions? People im metric Countries (Vast Majotity) are wondering how many inches in a cubit? :) :)
Internally, it uses Inches because Sketchup do so as well. However, go to the Option menu and select the unit you like, such as mm or cm and everything in Raylectron will be using that.
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Re: Using a lot of light power

Post by Support »

stevo1 wrote: Thu Jun 09, 2022 3:16 am One more question please. What settings should I use to make the glass better?
Select the material for your glass and convert it to "Glass (solid)", providing all the faces have the same material, from and back, inside and out. It's easy to get fooled when the front face is transparent but not the back because if you look at it from the front, it's transparent and think it's glass when in fact the back face is the default material and light can't go in from there, no refraction and no reflection.
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