clipka <ano### [at] anonymousorg> wrote:
> 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=41
0795
> > &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.
>
Yes, this is what I implement.

>
> > 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.)
>
> For a commercial sky rendering tool, OpenEXR output is probably
> mandatory. The format is comparatively complex though, so you'll
> probably want to use a library for that. Unfortunately (for you, not for
> POV-Ray ;)) the official library is written in C++, so you'd have to go
> for JNI to use that one. A few people seem to have set out to write
> OpenEXR libraries for Java, but at present none of those seem to stand
> out as the definitive choice, and their legal status may be too poorly
> defined for your purposes. (The official OpenEXR library is perfectly
> fine in that respect.)

Thank you for the information! I had no idea for these.

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