Full size sky?

[40oz]

I've asked a while back what the optimum height for a sky texture that doesn't repeat when using a software rendering source port that allows freelook up and down, and the answer I got was 240.

Now the trouble I'm having is putting it together. My test ports are Odamex, Zdaemon, and Zandronum, and so far I've gotten the best results with my 240 height sky graphic by splitting it into two separate patches. I cut the bottom portion of the sky at 128 units and set it at 0, 0 offsets, then the second patch which is the top half of the sky is set at 0, 128 offsets. (This makes the top half of the sky look like its on the bottom in the editor, but for some reason looks perfect in game.)

So far so good, except that in Zandronum, apparently the player can look up just a little bit higher than the player can in Odamex or Zdaemon, which makes the sky repeat. Also I have no idea how to make it look good in OpenGL, as it kinda stretches the bottom portion of the sky, and fades the top half into a solid middle color. (the sky I'm using is sort of a sunset, so ideally, it's brightest around the bottom and darker at the top)

What should I do to get my sky to look the best that it can in all source ports and in different renderers?

[plums]

40oz said:

Also I have no idea how to make it look good in OpenGL, as it kinda stretches the bottom portion of the sky, and fades the top half into a solid middle color. (the sky I'm using is sort of a sunset, so ideally, it's brightest around the bottom and darker at the top)

All (I think) OpenGL renders will stretch and fade a normal sky since most don't tile vertically, but GL Doom ports let you look up and down at unlimited angles. The best way to get a good looking sky is to make a skybox, but I haven't found any good and easy way to deform a normal sized sky image properly to fit a skybox curves without buying commercial software.

I've got a convoluted way to take a large rectangular image and change it into a skybox in Linux, if you want I can try it with your image... (if you're working with a larger source image, give me that instead of the Doom texture.)
edit: or if you want to try yourself: http://vinayhacks.blogspot.ca/2010/11/converting-equirectangular-panorama-to.html
This software does exist for Windows but I had a hard time setting it up properly.

There's also the issue of having different skybox definitions for different ports, though at least the GL versions of ZDoom and PrBoom+ use a compatible format.

[Mechadon]

I don't think you need to split the sky vertically like that, atleast not for Zandronum. It should be able to display it as one large patch (1024x240). I know certain ports don't support patch sizes that wide though, so that's when you want to chop it up into 256px chunks.

This is just a wild guess, but you could try making the sky 256px tall and see how it looks in Zandronum. I'm using 240px tall skies in Vela Pax and I don't have any issues with them tiling vertically in ZDoom with mouselook enabled. Is there an option in Zandronum that increases the view range of mouselook (maybe that already exists in ZDoom too, I have no idea)? You could force sky stretching in MAPINFO and see if that would work out ok; if the distance is small, the distortion might not be very noticeable.

Making it look good in OpenGL, at least how you probably want it to look, will be a bit more difficult. Obviously its hard to say without seeing the sky, but is there any chance you could manually offset the texture so that the top portion is closer to the horizon? You could also possibly make it into a skybox, but that sounds like it would be pretty difficult (I don't know anything about making them).

[Gez]

http://zdoom.org/wiki/Sky_stretching
The info there should apply to Zandronum as well.

[wesleyjohnson]

DoomLegacy uses rsky patches of size 256x240.

GIMP will rescale and stretch graphics, including ppm. I use it for making Doom graphics. I do not recommend stretching an existing sky as it does not look very good. And the port will do that itself if it needs to.