Discrepancy in Illuminance Calculations Using evalglare for HDR Images with Direct Sunlight Exposure

radiance-general
1

Hi everyone,

I have been using evalglare to calculate the vertical illuminance from an HDR image generated from RPICT Radiance. The image was captured under clear sky conditions using GENSKY. The command I used was: evalglare -V HDRimage.hdr

The scene depicted in the HDR image is an outdoor view with direct exposure to the sun. However, I have noticed that the illuminance values obtained from evalglare seem to be overestimated by a factor between 2 and 3.

I would appreciate your insights on the possible causes of this discrepancy. Additionally, I’m curious to know if evalglare is well-suited for such outdoor applications, especially when dealing with direct sunlight conditions.

Thank you in advance for your help and suggestions

2

It may simply be an issue of rendered resolution being too low to resolve the solar disk. What were the options you gave to rpict? How do you know the illuminance is off by a factor of 2 or 3? What were your numbers and how did you calculate them?

Cheers,
-Greg

3

That is correct, thanks, the results now are reasonable after increasing the resolution.