bevy/crates/bevy_render
m-edlund c323db02e0
Add sub_camera_view, enabling sheared projection (#15537)
# Objective

- This PR fixes #12488

## Solution

- This PR adds a new property to `Camera` that emulates the
functionality of the
[setViewOffset()](https://threejs.org/docs/#api/en/cameras/PerspectiveCamera.setViewOffset)
API in three.js.
- When set, the perspective and orthographic projections will restrict
the visible area of the camera to a part of the view frustum defined by
`offset` and `size`.

## Testing

- In the new `camera_sub_view` example, a fixed, moving and control sub
view is created for both perspective and orthographic projection
- Run the example with `cargo run --example camera_sub_view`
- The code can be tested by adding a `SubCameraView` to a camera

---

## Showcase


![image](https://github.com/user-attachments/assets/75ac45fc-d75d-4664-8ef6-ff7865297c25)

- Left Half: Perspective Projection
- Right Half: Orthographic Projection
- Small boxes in order:
  - Sub view of the left half of the full image
- Sub view moving from the top left to the bottom right of the full
image
  - Sub view of the full image (acting as a control)
- Large box: No sub view

<details>
  <summary>Shortened camera setup of `camera_sub_view` example</summary>

```rust
    // Main perspective Camera
    commands.spawn(Camera3dBundle {
        transform,
        ..default()
    });

    // Perspective camera left half
    commands.spawn(Camera3dBundle {
        camera: Camera {
            sub_camera_view: Some(SubCameraView {
                // Set the sub view camera to the left half of the full image
                full_size: uvec2(500, 500),
                offset: ivec2(0, 0),
                size: uvec2(250, 500),
            }),
            order: 1,
            ..default()
        },
        transform,
        ..default()
    });

    // Perspective camera moving
    commands.spawn((
        Camera3dBundle {
            camera: Camera {
                sub_camera_view: Some(SubCameraView {
                    // Set the sub view camera to a fifth of the full view and
                    // move it in another system
                    full_size: uvec2(500, 500),
                    offset: ivec2(0, 0),
                    size: uvec2(100, 100),
                }),
                order: 2,
                ..default()
            },
            transform,
            ..default()
        },
        MovingCameraMarker,
    ));

    // Perspective camera control
    commands.spawn(Camera3dBundle {
        camera: Camera {
            sub_camera_view: Some(SubCameraView {
                // Set the sub view to the full image, to ensure that it matches
                // the projection without sub view
                full_size: uvec2(450, 450),
                offset: ivec2(0, 0),
                size: uvec2(450, 450),
            }),
            order: 3,
            ..default()
        },
        transform,
        ..default()
    });

    // Main orthographic camera
    commands.spawn(Camera3dBundle {
        projection: OrthographicProjection {
          ...
        }
        .into(),
        camera: Camera {
            order: 4,
            ..default()
        },
        transform,
        ..default()
    });

    // Orthographic camera left half
    commands.spawn(Camera3dBundle {
        projection: OrthographicProjection {
          ...
        }
        .into(),
        camera: Camera {
            sub_camera_view: Some(SubCameraView {
                // Set the sub view camera to the left half of the full image
                full_size: uvec2(500, 500),
                offset: ivec2(0, 0),
                size: uvec2(250, 500),
            }),
            order: 5,
            ..default()
        },
        transform,
        ..default()
    });

    // Orthographic camera moving
    commands.spawn((
        Camera3dBundle {
            projection: OrthographicProjection {
              ...
            }
            .into(),
            camera: Camera {
                sub_camera_view: Some(SubCameraView {
                    // Set the sub view camera to a fifth of the full view and
                    // move it in another system
                    full_size: uvec2(500, 500),
                    offset: ivec2(0, 0),
                    size: uvec2(100, 100),
                }),
                order: 6,
                ..default()
            },
            transform,
            ..default()
        },
        MovingCameraMarker,
    ));

    // Orthographic camera control
    commands.spawn(Camera3dBundle {
        projection: OrthographicProjection {
          ...
        }
        .into(),
        camera: Camera {
            sub_camera_view: Some(SubCameraView {
                // Set the sub view to the full image, to ensure that it matches
                // the projection without sub view
                full_size: uvec2(450, 450),
                offset: ivec2(0, 0),
                size: uvec2(450, 450),
            }),
            order: 7,
            ..default()
        },
        transform,
        ..default()
    });
```

</details>
2024-10-01 14:11:24 +00:00
..
macros Simpler lint fixes: makes ci lints work but disables a lint for now (#15376) 2024-09-24 11:42:59 +00:00
src Add sub_camera_view, enabling sheared projection (#15537) 2024-10-01 14:11:24 +00:00
Cargo.toml bump async-channel to 2.3.0 (#15497) 2024-09-28 19:21:59 +00:00
README.md Add README.md to all crates (#13184) 2024-05-02 18:56:00 +00:00

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