Advanced topics

Read this page only if you need, it is not necessary for most users.

SceneSkies’ world materials

When you select a sky for display, a world datablock is created by the addon, and used in the current scene. It is created from a template, and filled with the HDR images loaded from the addon’s data folder. There are two world material templates: the standard one, and the more complex one for color tweaking.

Here is the standard world material:

_images/standard_world_material.jpg

Here is the complex world material:

_images/advanced_world_material.jpg

Feel free to edit them by hand. But keep in mind that:

  • the controls in the addon’s panel are shortcuts to the curves nodes, and hue-saturation-value nodes
  • your manual edits will be lost by default, the next time you select a sky. Check the addon’s preferences.

Creating your own collection

You can add your own collections of HDRIs, and use them via SceneSkies. For that, you must understand how SceneSkies’ collections are structured. Their structure always follows the same conventions, such as directory structure and file names. Follow those conventions for your own HDRIs and SceneSkies will detect and load them. I recommend you check the addon’s data folder, and inspect the collections you already have installed (even the sample collection) to quickly have a good idea of the conventions to follow.

Follow these steps:

1. create the proper folder structure

In the data folder,

  1. the first directory level is the collections. The name of each folder is the name of the corresponding collection
  2. in each collection folder are resolution folders. You can have several resolutions available for each collection. The name must be a number giving the exact x resolution (image width in pixels) of all the panoramas inside
  3. in the resolution folders are the panoramas folders. Their name can be anything you want
  4. in each panorama folder are the EXR images and other files

2. name the HDRIs properly

The only mandatory image map for each panorama is equi_main.exr, all the others are optional for color-tweaking.

If you want color-tweaking for a panorama, put the necessary maps (that will be combined to form the final panorama image) in the folder. All of them are optional, if one is missing, it simply won’t be loaded and used. For instance if your scene has no clouds, you can omit the two cloud maps, saving on both RAM and CPU. These maps are created in Terragen. You should enable the following render elements in Terragen: cloud direct, cloud indirect, atmosphere direct, atmosphere indirect, surface direct, surface indirect, surface emission. Then name the output files exactly like SceneSkies expects: see below.

3. add metadata to describe the panoramas (facultative)

Each panorama folder can have a description.json, in which you tell the sun/moon heading and sun/moon elevation. Heading is the rotation in degrees around global Z. 0° = in the positive Y direction, and then positive rotation happens in Blender’s coordinate system: 90° = -X, 180° = -Y, 270° = +X. You can enter negative values. Elevation is the rotation in degrees above the horizon between 0° and 90°: 0° means on the horizon, 90° means noon. Negative elevation means below the horizon, behind the Earth. Values above 90° should not be used.

This information is used by the thumbnail generator (in the next step) so that all the thumbnails show the sun / moon. If description.json is missing or incorrect for a panorama, the generator will simply ignore it and will still render the thumbnail but will show heading 0° and elevation about 45°. It will also print a message in the console about it during the rendering of the thumbnails, so you can pinpoint what panoramas have missing or incorrect description files.

Here is an example of description.json:

{
        "sun_or_moon_heading_degrees": 270.0,
        "sun_or_moon_elevation_degrees": 14.0
}

4. generate the thumbnails

Go to the addon’s folder (find its location in its description in Blender’s preferences). Open thumbnails_renderer.blend. You’ll see a script, you don’t need to understand it but there’s one setting you can change, at line 6. You can either let the script generate only the missing thumbnails, then set overwrite = False. Or you can re-generate all thumbnails even if they already exist with overwrite = True. When you’re ready, click the Run script button at the bottom of the text editor panel, or with the mouse in that panel press Alt + P. The script will scan all your installed panoramas, and generate the necessary thumbnails. It can take a while, so you should open Blender’s console beforehand, to see the progress.

Using the panoramas in other software

You can use SceneSkies’ HDRIs in any renderer that supports panorama EXR images in equirectangular projection. Load the equi_main.exr file.

For color tweaking, you have to mix 7 HDRIs maps by adding them together (addition color mode), if your renderer supports color mixing of several images to construct the final panorama. The 7 maps are:

  1. equi_atmoDirect.exr: direct light on the atmosphere
  2. equi_atmoIndirect.exr: indirect light on the atmosphere
  3. equi_cloudDirect.exr: direct light on the clouds
  4. equi_cloudIndirect.exr: indirect light on the clouds
  5. equi_surfDirect.exr: direct light on the ground and other surfaces
  6. equi_surfIndirect.exr: indirect light on the ground and other surfaces
  7. equi_surfEmit.exr: all surfaces emitting light, typically the sun