If there is no high poly mesh associated with this, the rays will miss and this area will be treated as empty, so the pixel padding from the other areas will bleed into this area. The easiest thing to do in this case would be to make a copy of your low poly mesh and use that as the high poly mesh for this area.
We've got a bunch of interconnecting tiles that fit together with rules to connect them and then I can paint the layout using the hex value of pixels with roads, rivers, towns or whatever in a PNG. There's also manual override in the map tool if I need an exact tile or orientation.
Whargoul's way is good. SEM on the wiki Plane will work OK as long as it's bump-mapped. Without a bump, it'll probably just reflect a single pixel from the spheremap. You could also bend the plane's vertex normals outward, so it reflects more of the spheremap.
eric: note for padding: "You can never have too much, ever, never ever ever have too much, its a non-existent problem having too much padding". I use like 32 pixels for everything, because well, why not?
Here is the link to everything used for the bake including the resulting normal map from Xnormal. Thanks Earthquake! https://www.dropbox.com/sh/58nauexstfzfc4m/AADLB21Fa2zPt_fJZQxyfDO0a?dl=0 Im afraid I dont quite understand the question. Aren't the pixel sizes all the same in this case?
I agree with the above post, but in my work I have noticed that the min mode doesnt work quite as expected, and will actually brighten some pixels, which I've had mess with grout on a few occasions. I usually multiply the grout back in afterwards to solve this.
I didn't say the missile/light stream was 720 degrees. But that's the exact same per pixel result I used to get. I was using the technique to try and create a texture for a vortex in a mockup of an old game I was making. So That's the first thing I thought of.
I pulled my inspiration from the original which was hodge podge of pixels in a side scrolling beat em up with not much info, leaving lots to interpretation. Everything that came after that, while interesting, wasn't what I desired out of this. The target was realistic and tough.
2048x2048 doesn't make sense for a sky hemisphere, 4096x1024 will use the same texture memory but will map much better to hemi. Correct: Wrong: You'll get much better horizon detail with 4:1 vs 1:1, for the same amount of pixels/memory use.
These could be from low edgepadding issues. Try setting the edgepadding to something like 4 or 5 -- this will bleed the pixels along the UV edges and eliminate artifacts like that. You might want to test the AO and Normals separately to see which map(s) is messing up.