This is the best method I have come up with in my experiments with seamless skyboxes:This is an example result in action.****
You'll need this
tiny program; it has a set of panorama-editing functions that we'll want to use. (Because a skybox is essentially a cut-up panorama.)
You'll also want to have an abstract brush on hand when you have to mask or clone-stamp; I use this
one. (Unless you're using photo reference (like me, in this case), and since I'm guessing you're drawing all of this manually - you probably don't need this.)****
First, draw your space-scape; we will be converting this image into an equirectangular panorama - this means all six of your skybox faces are already contained within this image, so make it large and make sure the image conforms to a 2:1 width-to-height ratio (For example, mine is 4096x2048).
Offset the image (in Photoshop, Filter > Other > Offset
, make sure Wrap Around
is selected) by half
to the right. (In my case, by 2048
The fun part; clone-stamp/mask or draw on top of the seam in the middle of the image.
Offset the image again to return it to the previous view.
Next, save this file (reccomend .TGA) and open it in HDRShop
. Click OK
on the dialog box that appears; it doesn't concern us.
Go to Image > Panorama > Panoramic Transformations
, you will get a new dialog box:1)
Set the Source Image
format to Latitude/Longitude
Set the Destination Image
format to be the same.3)
Set the Width
to your image's existing dimensions (check Source Image dimensions if unsure)4)
Select Arbitrary Rotation
, then click on Settings
; input 90
for the Z axis
Uncheck Use Bilinear Interpolation
; you will get an image with two prominent areas of distortion in the middle (right-click > Zoom Out
to get a better view), like this:
If you still have Photoshop open, (in HDRShop) go to File > Edit in Image Editor
, this will open the new image in Photoshop; proceed to stamp/mask away or draw on top of the distortions until happy with the result.
Save the file and open it in HDRShop once more. Again, go to Image > Panorama > Panoramic Transformations
as the Source Image format, but this time, however, pick Cubic Environment
as the Destination Image format. Now, depending on the resolution you want for your skybox faces to be, input one of the following for the Width
- for skybox faces that are 512x5123072
- for 1024x1024
(this is the one I'll use)6144
- for 2048x2048
(not recommended unless your source image is HUGE
Finally, click OK
. You should now get vertical cross cubemap configuration which you can cut up into six images and convert to a seamless skybox!