README.md

Map Skybox

(a Crusader Kings III modding utility)

This repository contains CK3 mod files which implement sky rendering on the map.

You can integrate this feature into your own mod by copying the files into your mod's file structure and making adjustments if necessary (see Integrating into Your Mod). Alternatively, you can load the contents of this repo as a separate mod in your playset, which might be useful if you just want to take several beauty shots of the map, mod/descriptor.mod is provided for this purpose.

The code has been updated to be compatible with CK3 version 1.12 (Scythe).

Table of Contents

1. Description
2. Integrating into Your Mod
3. Tweaks for Larger Maps
4. Under the Hood

Description

The sky is rendered via a skybox - a 6-sided box mesh with normals pointing inwards, which is placed as an object on the map, and to which a special sky pixel shader is applied. Game camera is unlocked (its min. angle is set to 0 via a define) to be able to actually look at the sky and appreciate its beauty. Additionally, shader files in this repo also contain Buck's fixes for borders and horizon rendering through the terrain, as well as a version of sky shader suitable for use in court room scenes.

Integrating into Your Mod

Use the following steps to integrate map sky rendering into your mod.

1. Copy the contents of gfx/models/mapitems and gfx/map/map_object_data into your mod's file structure.

2. Copy all of the .shader files that don't yet exist in your mod from gfx/FX. If your mod already has some of these shader files, you'll need to manually merge in changes from this repo's versions of these files into yours.

For convenience, all the changes necessary for map sky rendering are marked with MOD(map-skybox) comments in .shader files - you can just search for this string and copy/replace all pieces of code surrounded by this comment. Additionally, MOD(court-skybox) comments in court_scene.shader mark changes providing support for sky rendering in court room scene.

3. Copy gfx/map/environment/SkyBox.dds from this repo, if you want to use the sky texture it provides (can be seen in the demo GIF).

Alternatively, you can either take one of the cubemap images included in vanilla game (from vanilla gfx/map/environment or gfx/portraits/environments folders), or create your own skybox image and save it as gfx/map/environment/SkyBox.dds.

If going the latter route, make sure that your custom SkyBox.dds is using BC1/DX1 format and is saved as a cubemap ("Cube Map from crossed image" in Paint.NET) with mip-maps enabled.

4. Copy common/defines/graphic/SKYX_defines.txt from this repo, unless your mod already modifies ZFAR or ZOOM_STEPS_MIN_TILT defines.

5. If your mod's map size is the same as vanilla (8192x4096) or smaller, you're all set. Otherwise see the next section.

Tweaks for Larger Maps

If your map is larger than vanilla (as specified via WORLD_EXTENTS_X and WORLD_EXTENTS_Z defines), you'll need to modify a couple of things.

1. Either via mapeditor or by manually modifying gfx/map/map_object_data/SKYX_skybox.txt with a text editor, move the SKYX_skybox mesh to the middle of your map and resize it along X and Z axes so that it's a bit bigger than your map.

If you choose to use a text editor, you can do this by finding the line with transform= in gfx/map/map_object_data/SKYX_skybox.txt and changing the numbers there as follows:

Existing Number	Change to
4096.0	your WORLD_EXTENTS_X divided by 2
2048.0	your WORLD_EXTENTS_Z divided by 2
10000.0	your WORLD_EXTENTS_X plus 1000
5000.0	your WORLD_EXTENTS_Z plus 1000

2. Change ZFAR define in common/defines/graphic/SKYX_defines.txt (or your own defines file) to be about 1.5 times bigger than the larger of your map's sides.

So, for example, if your map dimensions are 10000x20000, set your ZFAR to 30000.

This is needed so that the skybox mesh is not clipped by the camera's far clipping plane when rendering, otherwise you'll see a black artifact when looking from one corner of the map at the opposite one.

So if you see something like this, it's probably due to your ZFAR being too small.

Under the Hood

Below is a short summary of the files included in this repo and the purpose they serve.

• gfx/models/mapitems/SKYX_skybox.mesh - the actual skybox mesh - a cube with inverted normals, 2.0 units in each dimension, origin in the center.
• gfx/models/mapitems/SKYX_skybox.asset - asset file defining SKYX_skybox_mesh based on the above mesh file and specifying SKYX_sky shader effect for it.
• gfx/map/environment/SkyBox.dds - cubemap texture used for the sky, may be replaced by a custom one as described above.
• gfx/map/map_object_data/SKYX_skybox.txt - map data file, placing a single instance of the SKYX_skybox_mesh in the middle of the map and scaling it to enclose the entire map; needs to be modified for larger-than-vanilla maps as described above.
• gfx/FX contains modified vanilla shader files, which introduce the following changes necessary to properly render the skybox.
  • pdxmesh.shader - defines SKYX_sky shader effect used to render the map skybox using the cubemap texture in SkyBox.dds.
  • court_scene.shader - defines SKYX_court_sky shader effect, which can be used to render skyboxes in court room scenes based on cubemap specified in their scene settings files.
  • pdxborder.shader - prevents borders from being rendered through terrain.
  • surroundmap.shader - prevents black line on the horizon from being rendered through terrain.
  • pdxwater.shader - removes black spaces along map edges with no water to prevent them from ruining the sky effect.
• common/defines/graphic/SKYX_defines.txt - changes camera-related defines to unlock map camera angles and moves far clipping plane further from the camera; needs to be modified for larger-than-vanilla maps as described above.