@cotty said:
I'm wondering where you will get the needed info for the high dynamic range from a single JPG...
How I've done it in the past is to create false exposure images and use an HDR creating software to juxtapose them into a single HDR.
It's tricky and fake but you can do it.
The things to take care are light sources. My theory is that if you lower your image brightness in any software like gimp, then duplicate the background layer, and screen it with the layer below, only the brightest parts will enhance. If you save the image and repeat the process, you will have several images that you can use for braketing and create an HDR.
It did work for me at the time, but eventually nowadays it isn't worth the trouble, anyway I've come up with my own sky system for Thea (development stalled) that is able to render images with the sky system 4x to 10x slower than with Thea's native sky, but also allows Thea to generate any sky.
Once I get the procedural right I'll give more info:
Here's a couple of images rendered with the system:
CASCA Sky Direct Render - 10 secs render .jpg
CASCA System on the fly 15 secs 2.jpg
CASCA System on the fly 15 secs 1.jpg
And a gif of the system in action:
http://i.imgur.com/dgWOYYI.gif