Quote from: D.A. Bentley on April 30, 2020, 11:49:08 AMThis would likely be an image with a contrast ratio (dynamic range) of 16:384:1 up to 1,024,000:1 or 14EV - 20EV. The problem I have encountered is I'm having trouble finding a tool that can accurately measure dynamic range, but I think FDR Tools is working the best. Photomatix Pro and Picturenaut seem way off.
Wouldn't the contrast ratio depend on what's in the scene, such as objects casting shadows, dark materials etc., or do you mean something else?
QuoteBecause Terragen is capable of rendering out 32-bit exr with a full range I would rather continue to just render out one hdr image, instead of fusing multiple renderings into an hdr (like when doing photography). For the past year I have been rendering single hdr images like this, but was mostly adjusting brightness levels in the scene by adjusting the sun strength, which could create unrealistic hot spots in and around the sun (i think). So that's why I am trying to figure out the best sun strength values to use, and then I can adjust the camera exposure to get the desired overall brightness of the image.
To better illustrate this lets consider a Standard Dynamic Range (SDR) or Low Dynamic Range (LDR) image is in a range of 0 - 1 (32bit channels), or 0 - 255 (8bit channels) while a High Dynamic Range (HDR) image can contain a range even greater than 0 - 1,000,000. I am trying to make sure that my terragen renderings are not putting all that extra brightness range all in and close to the sun, which would basically end up giving you a LDR image with an HDR sun. So basically this comes down to choosing the correct sun strength and camera exposure to control the Histogram Levels of the image being rendered.
In a scene without luminous/emissive objects, changing sunlight strength is exactly the same as changing camera exposure. I think you have three choices:
1) Leave sunlight strength the same in every image, only changing the exposure to compensate for the weather and time of day (as you would in photography).
2) Leave exposure the same (e.g. 1), only changing the sunlight. This has the advantage of allowing you to drop in different cameras without having to change their exposure, and you can save these atmosphere-and-sunlight setups for reuse in other projects, but it's a little bit backwards to how the real world worlds.
3) Use the same sunlight and exposure values for all images, letting sunset be darker than noon, and compensating in the destination renderer. Unfortunately if you do this the anti-aliasing won't be optimized for the desired appearance (e.g. if you render too dark, the renderer won't spend much time anti-aliasing dark areas which might be viewed more brightly later on, and if you render too bright it will spend less time anti-aliasing the bright areas which it thinks are overexposed even if they will be visible later on).
The choice between 1 and 2 is more about organization of your projects than anything else. They both render the same, as long as you don't have luminous (emissive) objects which are of course affected by exposure. Also, changing these things in Terragen will result in something similar - if not identical - to changing the multiplier in whatever renderer you load the EXR into for image based lighting, except that anti-aliasing won't be optimal if you render at sunlight/exposure values that don't look similar to what you'll end up with.
Choice 3 is not ideal if you care about quality and/or render times, because anti-aliasing is optimized for what's visible in the image at render time.
