Am 12.09.2016 um 08:53 schrieb And:
> I posted a POV-Ray SDL version sky-render program a few months ago.
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.5707b68461e083edaf5560460%40news.povray.org%3E/?ttop=410795
> &toff=50
> 
> But it renders very slow(when turns on secondary scattering). So I write it with
> Java currently. It performs 50X faster.

Make sure you do proper gamma handling. You'll want to use linear
brightness values for your computations, but (depending on file format)
will want to store them in non-linear gamma-encoded format.

Also, I imagine that skies might benefit a lot from spectral rendering,
i.e. using a ton of colour channels for computations, and only boil them
down to RGB format at the very end.


> This time, I get a bottleneck that I don't know how can I output image to an
> HDRI image format like .exr or .hdr. I just output a .png that Java build in. I
> need some help.

Unless you want to wrestle with JNI to call machine-specific compiled
code, I'd recommend to go for Radiance HDR (.hdr) format. It's pretty
simple to implement. (Make sure to use dithering though, as HDR is prone
to colour banding in gradients with saturated colours.)

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