Search found 120 matches

by chafouin
Wed Mar 04, 2020 7:18 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

Found what the 1.2 is: // Compute the maximum luminance possible with H_sbs sensitivity // maxLum = 78 / ( S * q ) * N^2 / t // = 78 / ( S * q ) * 2^ EV_100 // = 78 / (100 * 0.65) * 2^ EV_100 // = 1.2 * 2^ EV So they are actually doing the same. However... reading the 20 pages of that thread, it loo...
by chafouin
Tue Mar 03, 2020 5:16 pm
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

From my understanding (at least) the *.exr results should show direct luminance values. You are correct. This is in cd/m2 so if you set the tonemapper off and disable color management (show Raw values), the value you enter in your area light in Candela per Square meter (or artistic gain in LuxCore)...
by chafouin
Mon Mar 02, 2020 9:13 pm
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

I'm starting to become crazy with all these comparisons and pi factors, but Power to Lumen to Candela to Candela per square meter is correct in BlendLuxCore. There is a discrepancy comparing to Unreal at identical camera exposure, but this is not related to the new light units, and it was there befo...
by chafouin
Mon Mar 02, 2020 5:43 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

So if you have a point light source and this light source shall emit uniform amount of light in full sphere solid angle the formula is Intensity (cd) = luminous flux (lm) / solid ange (sr) Full sphere solid angle is 4*pi... so if you want to reach 1cd intensity your luminous flux must be 4*pi lm. T...
by chafouin
Sun Mar 01, 2020 6:08 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

Unfortunately I am still seeing the discrepancy between that and a 1 candela light, which is only getting me around 0.25 or so on a surface. Please check you have that version of the file: https://github.com/LuxCoreRender/BlendLuxCore/commit/a1ec8e36d1be0e928bf5780c21c7fac13d13290b#diff-759278cbe43...
by chafouin
Sat Feb 29, 2020 7:42 pm
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

As verification, if I set up the same exact scene in UE4 with a one candela light, I get exactly one lux of illuminance on the ground under the light. I have a different experience here where UE4 point light brightness is darker than LuxCore pointlight by a Pi factor. Did you compare using identica...
by chafouin
Sat Feb 29, 2020 9:53 am
Forum: Finished Work
Topic: Atmospheric Lake
Replies: 8
Views: 4833

Re: Atmospheric Lake

Congrats! I love that you picked "Caustics" to invite people to try LuxCoreRender, that's very smart ^^
by chafouin
Sat Feb 29, 2020 8:45 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

For what it's worth, I compared to Mitsuba and it seems that their point light is brighter by a 4*PI factor (I just compared two renders visually). Which doesn't help as this is way more than the brightness difference we see here when measuring the irradiance, but since Mitsuba is often regarded as ...
by chafouin
Fri Feb 28, 2020 5:07 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

If I switch it to 4Pi Lumens (one cd = 4pi l), I now get a slightly brighter result at 0.318. Close to pi, but maybe not a thing, given how close these all kinda are to pi. One would assume that 4pi lumens is the exact same as one candela, though. This was the inaccuracy I fixed this morning. Eithe...
by chafouin
Fri Feb 28, 2020 4:40 am
Forum: User Support
Topic: Light intensities and matching Cycles
Replies: 83
Views: 41319

Re: Light intensities and matching Cycles

It does a LOT of difference: https://github.com/LuxCoreRender/LuxCore/blob/e7dd877bfa32a1001d33a611f0b5116b5e08e042/src/slg/lights/spherelight.cpp#L150 As polyrhythm pointed out, it doesn't, actually. That's why I thought it wasn't even possible to make a point light, because I couldn't see a diffe...