You really thought I could tell you something interesting about environmental mapping? I just needed 4th image on first page, so this free downloaded web-site template could look normal. How could you fall for such an obvious trick? Just leave this page and embarrass me no longer...

Meh, ok... just use a direction vector as a color for the sky. You will get this nice psychodelic heaven...

Once you understood where is your up direction, just use simple dot of direction vector and up vector with interpolation between up (light blue) and horizontal (white) colors. Don't forget to clamp between 0 and 1.

Voila, now we have perfectly boring morning sky... I liked acid heaven more...