Allow a single asset to contain multiple data

[RiscadoA]

Problem

Our asset flow lacks support for non-trivial asset handling.

The following scenario is a good example of this:

• UI Image elements use a render device (GPU) texture.
• That render device texture is created by sending an image to the GPU/render device.
• The image can be loaded from a file.

Currently, we can tackle this by providing an Image asset type, which loads a .png or equivalent. Then, on the UI side, we keep a Asset<Image> field on a component, and the UI code must manually manage the render device texture creation. This is cumbersome and error prone, and this is only one of the examples - we also have a similar situation with voxel grids.

Solution

A single asset (UUID) should be able to contain multiple data types. For example, taking the image example once again, we could have two asset types: Image, and Texture. The UI would store an Asset<Texture>, keeping a reference to only the GPU/render device texture asset. When loading texture data for a given asset, the TextureBridge load method is called, which internally loads the Image data of the same asset, and creates a render device texture. As no reference is kept to the Image data, it can be unloaded, keeping only the Texture part.

To sum it up, we should:

• Identify asset data through their type and UUID, not only by their UUID.
• Change asset meta files to not contain the data extension (i.e., instead of image.png.meta, just image.meta).

[RiscadoA]

After thinking about this a bit further, I came to the conclusion that this might not be such a good idea, as multiple 'source' assets may need to be exported multiple times, with different options. For example, it should be possible to create multiple font atlas assets from a single font asset.