RID Spam and Broken Temp Normal Map Generation

[outobugi]

Recreate issue:

1. Add albedo and normal map for it
2. Add a second surface without a normal map

[TokisanGames]

When creating a new blank surfarce the terrain in the viewport suddenly shifts and gains more contrast. Also there are many RID errors in the console. Both are visible in GamesFromScratch's video and people noted "bruh 29,000 errors".

Through debugging I found that the invalid RID is in the generated normal texture. This error persists anytime you do anything with that map all the way to complaints while freeing.

The cause is here:

https://github.com/outobugi/Terrain3D/blob/2e2457f2c0e489cbbc86d59265b56cc275dcc5dd/src/terrain_3d_storage.cpp#L165-L167

20 lines above, the albedo generation is nearly identical. The albedo image is Color(1.0f, 0.0f, 1.0f, 1.0f). After compression the resulting image is format 19: DXT5.

The only different to the code here is the image, which is filled with Color(0.5f, 0.5f, 1.0f, 1.0f). After compression the resulting image is format 17: DXT1!!??

Then the rendering server complains about the different formats, the normal map RID is invalid, and we get error spam.

Terrain3D::create: 0: <Image#-9223370263553314751>, empty: false, size: (1024, 1024), format: 19
Terrain3D::create: 1: <Image#-9223370263536537530>, empty: false, size: (1024, 1024), format: 19
Terrain3D::create: 2: <Image#-9223370263519760315>, empty: false, size: (1024, 1024), format: 17
Terrain3D::create: RenderingServer texture_2d_layered_create
ERROR: Condition "p_layers[i]->get_format() != valid_format" is true.
   at: texture_2d_layered_initialize (servers/rendering/renderer_rd/storage_rd/texture_storage.cpp:884)

The solution is to change the line to this, which forces it to use alpha.

img->compress_from_channels(Image::COMPRESS_S3TC, Image::USED_CHANNELS_RGBA);

Just in case, I changed it for both albedo and normal. Now we can add a blank surface and there are no errors, no visual change to the terrain, and we can paint with a null texture, which comes out as fuscia.