Struct tetra::graphics::Camera

pub struct Camera {
    pub position: Vec2<f32>,
    pub rotation: f32,
    pub zoom: f32,
    pub viewport_width: f32,
    pub viewport_height: f32,
    // some fields omitted
}

A camera that can be used to transform the player's view of the scene.

To apply the transformation, call the as_matrix method and pass the resulting Mat4 to graphics::set_transform_matrix. To disable it, call graphics::reset_transform_matrix.

The camera's matrix is cached internally as an optimization. After adjusting parameters on the camera, you can call the update method to recalculate the matrix.

Examples

The camera example demonstrates how a camera can be used to transform a simple scene.

Fields

position: Vec2<f32>

The position of the camera.

Note that this defines the center point of the view, rather than the top-left. This makes it easy to position the camera relative to your game objects - for example, to focus the camera on the player, you can just set the camera position to match the player's position.

You may need to take this behaviour into account when positioning the camera, however. For example, if the viewport width or height is an odd number, setting the position to a whole number will mean that the view will not be aligned with the pixel grid, which may cause issues for pixel-perfect rendering.

rotation: f32

The rotation of the camera, in radians.

zoom: f32

The zoom level of the camera.

This is expressed as a scale factor - 0.5 will shrink everything by half, while 2.0 will make everything twice as big.

viewport_width: f32

The width of the camera's viewport.

This is primarily used for calculating where the center of the screen is, and usually should match the size of the target you're currently rendering to (e.g. the screen, or a Canvas).

viewport_height: f32

The height of the camera's viewport.

This is primarily used for calculating where the center of the screen is, and usually should match the size of the target you're currently rendering to (e.g. the screen, or a Canvas).

Implementations

impl Camera

pub fn new(viewport_width: f32, viewport_height: f32) -> Camera

Creates a new camera with the given viewport size.

The provided size usually should match the size of the target you're currently rendering to (e.g. the screen, or a Canvas).

pub fn with_window_size(ctx: &Context) -> Camera

Creates a new camera, with the viewport size set to match the size of the window.

This is a useful shortcut if your game renders at a 1:1 ratio with the game window. If you're rendering to a differently sized target (e.g. a Canvas or a ScreenScaler), then you should use call new with the target size instead.

Note that if the window is resized, the camera's viewport size will not automatically update. If you need to keep the window size and the viewport size in sync, then call set_viewport_size in State::event when Event::Resized is fired.

pub fn set_viewport_size(&mut self, width: f32, height: f32)

Sets the size of the camera's viewport.

The provided size usually should match the size of the target you're currently rendering to (e.g. the screen, or a Canvas).

pub fn update(&mut self)

Recalculates the transformation matrix, based on the data currently contained within the camera.

pub fn as_matrix(&self) -> Mat4<f32>

Returns the current transformation matrix.

Pass this to graphics::set_transform_matrix to apply the transformation to your scene. To disable the transformation, call graphics::reset_transform_matrix.

The matrix is cached internally, so calling this method multiple times will not cause it to be recalculated from scratch.

pub fn project(&self, point: Vec2<f32>) -> Vec2<f32>

Projects a point from world co-ordinates to camera co-ordinates.

pub fn unproject(&self, point: Vec2<f32>) -> Vec2<f32>

Projects a point from camera co-ordinates to world co-ordinates.

pub fn mouse_position(&self, ctx: &Context) -> Vec2<f32>

Returns the mouse's position in camera co-ordinates.

This is a shortcut for calling project(input::get_mouse_position(ctx)). As such, it does not take into account any other transformations being made to the view (e.g. screen scaling).

pub fn mouse_x(&self, ctx: &Context) -> f32

Returns the X co-ordinate of the mouse's position in camera co-ordinates.

This is a shortcut for calling project(input::get_mouse_position(ctx)).x. As such, it does not take into account any other transformations being made to the view (e.g. screen scaling).

pub fn mouse_y(&self, ctx: &Context) -> f32

Returns the Y co-ordinate of the mouse's position in camera co-ordinates.

This is a shortcut for calling project(input::get_mouse_position(ctx)).y. As such, it does not take into account any other transformations being made to the view (e.g. screen scaling).

pub fn visible_rect(&self) -> Rectangle

Calculates the visible rectangle of the camera.

When used on a rotated camera, this will return the smallest rectangle that contains the full camera viewport.

Note that this method does not take into account any other transformations being made to the view (e.g. screen scaling).

Trait Implementations

impl Clone for Camera

pub fn clone(&self) -> Camera

Returns a copy of the value.

pub fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Camera

pub fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.