I was looking at different ideas presented for showing a general skybox and I read that there is two main ones, Skybox and Skydome. However, no matter how hard I try I can not find anything on how to actually set either one of these up. Does anyone have a tutorial or a demo project on how to do this?

Well I think you should use the skybox, its easy and it work a bit like this: You have an inverted box ( from the inside ) and apply textures ( seamsless skytextures ) on each side. Than you render it with the zbuffer off.

For your first sky, I'd recommend a skybox due to its simplicity. However, I recently implemented this and was unhappy with it as no matter how much I tweaked, there were artifacts at the edges/corners. I've implemented domes before and they were much better, but you still get artifacts at the poles/where the texture edges meet. I found an article on 'sky planes' which are a nice alternative to boxes/domes - one advantage over domes is that you dont have to wrap the texture round it and so you dont get artifacts where the two texture edges join up.

http://www.hyzgame.com.cn/CMGDK/Download/Sky%20Domes.pdf (pdf) is the article (scroll down about half way for the skyplanes).

But I'm using a strange method of generating sky which might suit planes better - basically instead of using a texture I'm doing all the color calculation in the pixel shader using a kind of ray tracing to determine what color the sky should be at that pixel. Using a few mathmatical equations you can take input of just the ray and produce the sun and a nice fading horizon. The drawback on this method is its more computationally demanding than just doing a single texture lookup, but it has almost no impact on the framerate.

A couple of sample images (I've not yet implemented bloom/HDR - they are next on my todo list, after trees :) ):



If you are interested, the pixel shader looks like this:

...
float4 Out;
float simil = (0.5 + 0.5*dot(normalize(In.Pos-float3(0.0, -skyY, 0.0)), -normalize(sunDirection)));

//float azimuth = atan2(In.Pos.z, In.Pos.x);
float base = length(float2(In.Pos.x, In.Pos.z));
float zenith = atan2(In.Pos.y+skyY, base)/3.14159;

//float base_sun = length(float2(sunDirection.x, sunDirection.z));
//float azimuth_sun = atan2(-sunDirection.z, -sunDirection.x);
//float zenith_sun = atan2(-sunDirection.y, base);

float br = (1.5 - pow(saturate(zenith),0.25));
float3 zenfade = skyColor*br;
float sunfade = pow(simil,500.0) + saturate(pow(simil+0.01,50.0))/5.0 + pow(simil,1.5)*0.5;//saturate();
Out = skyColor*br*saturate(1.0-sunfade) + sunColor*sunfade*1.02;
return Out;
...

One thing that annoys me about this code is the amount of constants in it that had to be painstakingly determined by trial and improvement, its not a nice method but I think it beats the alternative of fully implementing the 'atmospheric scattering' technique.

[Edited by - EvilDonut on July 23, 2008 1:39:39 PM]

Quote:Original post by EvilDonut
However, I recently implemented this and was unhappy with it as no matter how much I tweaked, there were artifacts at the edges/corners.

Did you try setting the clamp texture address mode? If you don't do this you will most likely have artefacts on your texture edges.