First of all, a big thanks to Tim - Akenine-Moller &Co. is indeed quite an interesting read, and in addition to gaining a better understanding, I've so far experimented successfully with a heightfield for parallax and normal mapping and a simple irrandiance map instead of the ambient term in lighting.
For those not inclined to read through a longer email, my question up front: I have a function, I want a texture holding the function values pairs - how do I map this without editing every pixel offline? And can we do this also online? Where is for instance the 3d noise texture defined and filled - is it simple to change the procedure? For those interested in the context: I have managed to create quite compelling terrain visuals from close-up (see here http://www.flightgear.org/forums/viewtopic.php?f=47&t=16884&start=15#p162613 for two examples), but rendering seems to get too slow too soon for anything really fancy (of course, a big roadblock is that I'm implementing all this on top of atmospheric light scattering which is slow to begin with - I think in the default light and fog scheme it might run with decent speed). One problem that really kills framerate is de-tiling. In order to de-tile properly, one needs to mix noise from different wavelengths such that the interference creates a pattern with a much larger periodicity. Three wavelengths usually do the job well, two are marginally acceptable, one is quite bad. So, for each texture component (snow, gradient texture, detailed texture, height map, fog) I ideally need three noise wavelengths. In the current 3d noise, noise[0] contains structures with a qualitatively different distribution, so I have to discard that component. noise[3] is too fine and runs into texture resolution problems, so I have to discard that as well. Since the noise pattern associated with different texture components needs to be uncorrelated (otherwise there's yet another form of tiling around the corner) I need to do different noise lookups for every texture component, arranging them in a slightly different wavelength interval. And that's a lot of texture3D() calls which really make the system slow. I could do it in half the time if I would get 4 useful components for every texture3D() call, but that requires that I either create a suitable texture offline or change the way it is done in the code (I'm also exploring if there is perhaps a function that evaluates faster than a texture lookup call...). Somewhat inversely, I'm also wondering if a simple texture1D() lookup might not be faster than evaluating the light function e / pow((1.0 + a * exp(-b * (x-c)) ),(1.0/d)) three times to get an (rgb)-triplet. However, I have no clue how to dump the function into a texture without hand-crafting every pixel. Finally, I think given that we have cloud position and sizes available, it'd be fairly trivial to cast that into a function that defines a shadow-map for clouds (I would not render the clouds to create that map, first because of transparency, second because they're really billboards and likely to come out wrong, third because the map wouldn't change fast and finally because it's faster to do one analytical function per cloudlet than to go through the 40 texture sheets that are in a cloudlet. So, any pointers along that front would be appreciated for a number of reasons... Thanks in advance! * Thorsten ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
