This tutorial will show you how to create a Skybox. When created and used correctly, skyboxes can add depth and atmosphere to a game.
Skyboxes are made up of six individual images which are wrapped into a cube. The reason why a skybox appears to be panoramic (you can see it in all directions without the impression of being inside a cube) is because the images are made to be perfectly aligned to each other. Making a skybox completely from scratch goes beyond the scope of this tutorial, so you must find these images yourself. However, this should be an easy task since skyboxes are so widely used across all kinds of games.
Next, you must re-size your images to 256x256 pixels. This can be done with any image editing tool; Microsoft Paint or Paint.NET are both good choices. After this, upload your images to Roblox as Decals.
It is very important that you re-size all six of your images. If you leave them at their original resolution, then the Roblox Decal Builder will downsize them and create artifacts (which you don't want on your skybox).
All skyboxes in Roblox are contained in the Sky object, so you must create one and place it in Lighting. You may have already noticed some properties called things like "SkyboxBk" and "SkyboxDn". The last two letters of these properties refer to what side of the skybox the specified image is going to be on (Back, Down, etc.). These are the properties where you will be placing your images' asset IDs.
To get the asset IDs of your images, simply take the numbers at the end of the URL at the top of your browser window and subtract 1. This number goes at the end of "rbxassetid://" (More information on Roblox content). When putting your asset ID URLs into the Sky object, make sure that the images you put in correspond to the correct property.
If you've done everything correctly, you should now have a complete skybox. You could save it now, or you could change some Lighting properties in order to make it fit better into the game.
The most effective properties for this purpose are OutdoorAmbient and ShadowColor. These properties change the outdoor light color and the color of shadows. It is important to remember that these only work if you have the GlobalShadows property checked.
To give a realistic effect, these two properties can be changed to have a slight bend towards the approximate color of your skybox. Remember that there are no rules and you can change these properties to whatever you like.
Congratulations, you just finished a skybox! From here, you can upload your skybox for everyone to use, or you can keep it for yourself to use in your own places.