HPL2/Tutorials/Convert HDRI to skyboxes

This tutorial describes how to convert HDRI images to a DDS skybox that works in HPL2.

For this tutorial you will need an HDRI of your choice (there's plenty of these to be found for free online) and GIMP.

Converting the HDR to cube textures

1. Use this online tool to convert your HDR image.
2. In the export settings, make sure to pick the PNG format and the 3rd export option (6 separate square images).
3. Pick a resolution. Amnesia is a relatively low-resolution game, so 1024 should be enough.
4. Download the resulting zip archive.
5. Extract the archive. There should be 6 images titled nx, px, ny, py, nz, pz (n=negative, p=positive, x,y,z are the 3D axises).

Assembling the DDS texture

Start GIMP.

Tip: You can open a cubemap that works in Amnesia to see how the file is organised.

1. Import all 6 images (you can drag and drop the files into GIMP). The filenames should turn into layer names.
2. Change the layer names (click on layer and press F2 or doubleclick) according to this naming scheme:
   • main surface (positive/negative x/y/z)
3. You should end up with 6 layers named like this:
   • main surface (positive x)
   • main surface (negative x)
   • main surface (positive y)
   • main surface (negative y)
   • main surface (positive z)
   • main surface (negative z)

The layers must be called like this or you won't be able to export the image as a cubemap. Their order doesn't matter, however.

Exporting from GIMP

Now that the structure is ready, pick File -> Export as. Then:

• Set the image file location and then the extension to .dds. Click export. This will open export settings.
• (Optional) Set the compression to DXT5. This compression algorithm is lossy, but the quality loss shouldn't be very noticeable.
• Set "Save" to "as cube map" and export.

Your newly made DDS skybox should now work in the Level Editor!