# Objective
- No point in keeping Meshes/Images in RAM once they're going to be sent
to the GPU, and kept in VRAM. This saves a _significant_ amount of
memory (several GBs) on scenes like bistro.
- References
- https://github.com/bevyengine/bevy/pull/1782
- https://github.com/bevyengine/bevy/pull/8624
## Solution
- Augment RenderAsset with the capability to unload the underlying asset
after extracting to the render world.
- Mesh/Image now have a cpu_persistent_access field. If this field is
RenderAssetPersistencePolicy::Unload, the asset will be unloaded from
Assets<T>.
- A new AssetEvent is sent upon dropping the last strong handle for the
asset, which signals to the RenderAsset to remove the GPU version of the
asset.
---
## Changelog
- Added `AssetEvent::NoLongerUsed` and
`AssetEvent::is_no_longer_used()`. This event is sent when the last
strong handle of an asset is dropped.
- Rewrote the API for `RenderAsset` to allow for unloading the asset
data from the CPU.
- Added `RenderAssetPersistencePolicy`.
- Added `Mesh::cpu_persistent_access` for memory savings when the asset
is not needed except for on the GPU.
- Added `Image::cpu_persistent_access` for memory savings when the asset
is not needed except for on the GPU.
- Added `ImageLoaderSettings::cpu_persistent_access`.
- Added `ExrTextureLoaderSettings`.
- Added `HdrTextureLoaderSettings`.
## Migration Guide
- Asset loaders (GLTF, etc) now load meshes and textures without
`cpu_persistent_access`. These assets will be removed from
`Assets<Mesh>` and `Assets<Image>` once `RenderAssets<Mesh>` and
`RenderAssets<Image>` contain the GPU versions of these assets, in order
to reduce memory usage. If you require access to the asset data from the
CPU in future frames after the GLTF asset has been loaded, modify all
dependent `Mesh` and `Image` assets and set `cpu_persistent_access` to
`RenderAssetPersistencePolicy::Keep`.
- `Mesh` now requires a new `cpu_persistent_access` field. Set it to
`RenderAssetPersistencePolicy::Keep` to mimic the previous behavior.
- `Image` now requires a new `cpu_persistent_access` field. Set it to
`RenderAssetPersistencePolicy::Keep` to mimic the previous behavior.
- `MorphTargetImage::new()` now requires a new `cpu_persistent_access`
parameter. Set it to `RenderAssetPersistencePolicy::Keep` to mimic the
previous behavior.
- `DynamicTextureAtlasBuilder::add_texture()` now requires that the
`TextureAtlas` you pass has an `Image` with `cpu_persistent_access:
RenderAssetPersistencePolicy::Keep`. Ensure you construct the image
properly for the texture atlas.
- The `RenderAsset` trait has significantly changed, and requires
adapting your existing implementations.
- The trait now requires `Clone`.
- The `ExtractedAsset` associated type has been removed (the type itself
is now extracted).
- The signature of `prepare_asset()` is slightly different
- A new `persistence_policy()` method is now required (return
RenderAssetPersistencePolicy::Unload to match the previous behavior).
- Match on the new `NoLongerUsed` variant for exhaustive matches of
`AssetEvent`.
# Objective
The quality of Bevy's text rendering can vary wildly depending on the
font, font size, pixel alignment and scale factor.
But this situation can be improved dramatically with some small
adjustments.
## Solution
* Text node positions are rounded to the nearest physical pixel before
rendering.
* Each glyph texture has a 1-pixel wide transparent border added along
its edges.
This means font atlases will use more memory because of the extra pixel
of padding for each glyph but it's more than worth it I think (although
glyph size is increased by 2 pixels on both axes, the net increase is 1
pixel as the font texture atlas's padding has been removed).
## Results
Screenshots are from the 'ui' example with a scale factor of 1.5.
Things can get much uglier with the right font and worst scale
factor<sup>tm</sup>.
### before
<img width="300" alt="list-bad-text"
src="https://github.com/bevyengine/bevy/assets/27962798/482b384d-8743-4bae-9a65-468ff1b4c301">
### after
<img width="300" alt="good_list_text"
src="https://github.com/bevyengine/bevy/assets/27962798/34323b0a-f714-47ba-9728-a59804987bc8">
---
## Changelog
* Font texture atlases are no longer padded.
* Each glyph texture has a 1-pixel wide padding added along its edges.
* Text node positions are rounded to the nearest physical pixel before
rendering.
This makes the [New Bevy Renderer](#2535) the default (and only) renderer. The new renderer isn't _quite_ ready for the final release yet, but I want as many people as possible to start testing it so we can identify bugs and address feedback prior to release.
The examples are all ported over and operational with a few exceptions:
* I removed a good portion of the examples in the `shader` folder. We still have some work to do in order to make these examples possible / ergonomic / worthwhile: #3120 and "high level shader material plugins" are the big ones. This is a temporary measure.
* Temporarily removed the multiple_windows example: doing this properly in the new renderer will require the upcoming "render targets" changes. Same goes for the render_to_texture example.
* Removed z_sort_debug: entity visibility sort info is no longer available in app logic. we could do this on the "render app" side, but i dont consider it a priority.
Extend the Texture asset type to support 3D data
Textures are still loaded from images as 2D, but they can be reshaped
according to how the render pipeline would like to use them.
Also add an example of how this can be used with the texture2DArray uniform type.
Use glyph_brush_layout and add text alignment support
Co-authored-by: Olivier Pinon <op@impero.com>
Co-authored-by: tigregalis <anak.harimau@gmail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
