Black sun disk when converting .exr into .hdr ?

[paq]

Hello,

Goal : Create a spherical and stereographic HDR sky using terragen .exr output.

I'm just trying to figure out what's the problem with terragen sun disk.

As soon as you try to convert .exr terragen files into either an .hdr format, or a low dynamic range format, the sun disk turn to black, or pink, or any other crazy colors.

Ptgui also give crazy result when trying to tone map .exr terragen skies, not a big deal as I only want .hdr (so no tone mapping), but PTGUI just failed to export an .exr stichting result (I have to bug report this, but I'm not sure where to start).

I'm not really sure what's the side effect of disabling the sun disk visibility into terragen. I was hoping to find a solution to keep it on in my hdr sky, because with some render engine (modo, maxwell), this disk could help to create sharp shadows using hdr lighting only ... well in theory because so far I wasnt able to test it 

And if it's not a Terragen mistake, which panorama stiching software can I use to build spherical and stereographic .exr skies ?

- Ptgui failed with my files (I have big black square in the sun area)
- Hugin do not open .exr  ... and converting .exr into .hdr = black sun
- Autodesk stiching software seems to handle the .exr pretty well, but there is no stereographic output, and no way to position the 5 terragen images in an numerical way.

[Matt]

This happens because Terragen's sun is too bright for some image formats (or conversion methods) to handle. You can decrease the brightness of the sun pixels by increasing the sun's visible disc diameter. Each pixel brightness is then reduced to compensate for the increased surface area, so the total output of the sun is the same.

The default diameter is 0.5 degrees, which is very close to how the Sun appears from Earth. First, try with a much larger diameter (e.g. 5) to see if it solves the problem. If it does, try smaller values to find what you can get away with, because 5 would produce very soft shadows.

Matt

[paq]

Hi Matt,

Thank you so much !!!

The result is very nice with a sun degree at 1. I'll try to reduce it a little bit more to see where is the limit.
So here's a little render test, using modo environment importance sampling, and off course no light.

Terragen dynamic range is huge !

[Dune]

because 5 would produce very soft shadows

Does it indeed? I have to try that.

[Matt]

because 5 would produce very soft shadows

Does it indeed? I have to try that.

If you use the render as an environment to light the scene in another renderer, e.g. Modo, Maxwell, VRay, then yes, the size of the sun will affect the softness of the shadows because the visible sun is now creating the lighting. In Terragen, the visible disc is independent of the soft shadows, but of course you can set the soft shadow diameter to 5 to get soft shadows if you like.

Matt

[Matt]

Hi Matt,

Thank you so much !!!

The result is very nice with a sun degree at 1. I'll try to reduce it a little bit more to see where is the limit.
So here's a little render test, using modo environment importance sampling, and off course no light.

Terragen dynamic range is huge !

Yep, better than an HDR photograph

Matt

[midnight_stories]

This info is worth its weight in gold, been scratching my head for the last 3 days.
and just increasing the Deg worked straight away plus now I can do soft shadows if I want.
It works perfect !

[TheBadger]

Yep, better than an HDR photograph

Matt

That in its self is pretty remarkable, really.