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use super::Rectangle;
use crate::input;
use crate::math::{Mat4, Vec2, Vec3};
use crate::window;
use crate::Context;
/// 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`](crate::graphics::set_transform_matrix`).
/// To disable it, call [`graphics::reset_transform_matrix`](crate::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`](https://github.com/17cupsofcoffee/tetra/blob/main/examples/camera.rs)
/// example demonstrates how a camera can be used to transform a simple
/// scene.
#[derive(Debug, Clone)]
pub struct Camera {
/// 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.
pub position: Vec2<f32>,
/// The rotation of the camera, in radians.
pub rotation: f32,
/// The scaling applied by the camera.
pub scale: Vec2<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`).
pub viewport_width: 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`](crate::graphics::Canvas)).
pub viewport_height: f32,
matrix: Mat4<f32>,
}
impl 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`](crate::graphics::Canvas)).
pub fn new(viewport_width: f32, viewport_height: f32) -> Camera {
Camera {
position: Vec2::zero(),
rotation: 0.0,
scale: Vec2::one(),
viewport_width,
viewport_height,
matrix: Mat4::translation_2d(Vec2::new(viewport_width / 2.0, viewport_height / 2.0)),
}
}
/// 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`](crate::graphics::Canvas) or a
/// [`ScreenScaler`](crate::graphics::scaling::ScreenScaler)), then you should use call [`new`](Self::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`](Self::set_viewport_size) in [`State::event`](crate::State::event) when
/// [`Event::Resized`](crate::Event::Resized) is fired.
pub fn with_window_size(ctx: &Context) -> Camera {
let (width, height) = window::get_size(ctx);
Camera::new(width as f32, height as 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`](crate::graphics::Canvas)).
pub fn set_viewport_size(&mut self, width: f32, height: f32) {
self.viewport_width = width;
self.viewport_height = height;
}
/// Recalculates the transformation matrix, based on the data currently contained
/// within the camera.
pub fn update(&mut self) {
self.matrix = Mat4::translation_2d(-self.position);
self.matrix.rotate_z(self.rotation);
self.matrix
.scale_3d(Vec3::new(self.scale.x, self.scale.y, 1.0));
self.matrix.translate_2d(Vec2::new(
self.viewport_width / 2.0,
self.viewport_height / 2.0,
));
}
/// Returns the current transformation matrix.
///
/// Pass this to [`graphics::set_transform_matrix`](crate::graphics::set_transform_matrix`)
/// to apply the transformation to your scene. To disable the transformation, call
/// [`graphics::reset_transform_matrix`](crate::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 as_matrix(&self) -> Mat4<f32> {
self.matrix
}
/// Projects a point from world co-ordinates to camera co-ordinates.
pub fn project(&self, point: Vec2<f32>) -> Vec2<f32> {
let mut proj = Vec2::new(
(point.x - self.viewport_width / 2.0) / self.scale.x,
(point.y - self.viewport_height / 2.0) / self.scale.y,
);
proj.rotate_z(-self.rotation);
proj += self.position;
proj
}
/// Projects a point from camera co-ordinates to world co-ordinates.
pub fn unproject(&self, point: Vec2<f32>) -> Vec2<f32> {
let mut unproj = point - self.position;
unproj.rotate_z(self.rotation);
unproj.x = unproj.x * self.scale.x + self.viewport_width / 2.0;
unproj.y = unproj.y * self.scale.y + self.viewport_height / 2.0;
unproj
}
/// Returns the mouse's position in camera co-ordinates.
///
/// This is a shortcut for calling [`project(input::get_mouse_position(ctx))`](Self::project).
/// As such, it does not take into account any other transformations
/// being made to the view (e.g. screen scaling).
pub fn mouse_position(&self, ctx: &Context) -> Vec2<f32> {
self.project(input::get_mouse_position(ctx))
}
/// 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`](Self::project).
/// 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 {
self.mouse_position(ctx).x
}
/// 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`](Self::project).
/// 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 {
self.mouse_position(ctx).y
}
/// 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).
pub fn visible_rect(&self) -> Rectangle {
let viewport_width = self.viewport_width / self.scale.x;
let viewport_height = self.viewport_height / self.scale.y;
let half_viewport_width = viewport_width / 2.0;
let half_viewport_height = viewport_height / 2.0;
if self.rotation.abs() > f32::EPSILON {
// Rotate the top-left and bottom-left point, then get the max x and y from both vectors.
// This is the range of the bounding box that contains this rectangle.
let mut top_left = Vec2::new(-half_viewport_width, -half_viewport_height);
let mut bottom_left = Vec2::new(-half_viewport_width, half_viewport_height);
top_left.rotate_z(self.rotation);
bottom_left.rotate_z(self.rotation);
let largest_x = f32::max(top_left.x.abs(), bottom_left.x.abs());
let largest_y = f32::max(top_left.y.abs(), bottom_left.y.abs());
let left = self.position.x - largest_x;
let top = self.position.y - largest_y;
// The largest x and y are the distance from the center, so the width is twice that.
let width = largest_x * 2.0;
let height = largest_y * 2.0;
Rectangle {
x: left,
y: top,
width,
height,
}
} else {
// Quick happy path with no rotation
let left = self.position.x - half_viewport_width;
let top = self.position.y - half_viewport_height;
Rectangle {
x: left,
y: top,
width: viewport_width,
height: viewport_height,
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn point_projections() {
let mut camera = Camera::new(128.0, 256.0);
let proj_initial = camera.project(Vec2::zero());
let unproj_initial = camera.unproject(proj_initial);
assert_eq!(proj_initial, Vec2::new(-64.0, -128.0));
assert_eq!(unproj_initial, Vec2::zero());
camera.position = Vec2::new(16.0, 16.0);
let proj_positioned = camera.project(Vec2::zero());
let unproj_positioned = camera.unproject(proj_positioned);
assert_eq!(proj_positioned, Vec2::new(-48.0, -112.0));
assert_eq!(unproj_positioned, Vec2::zero());
camera.scale.x = 2.0;
camera.scale.y = 4.0;
let proj_zoomed = camera.project(Vec2::zero());
let unproj_zoomed = camera.unproject(proj_zoomed);
assert_eq!(proj_zoomed, Vec2::new(-16.0, -16.0));
assert_eq!(unproj_zoomed, Vec2::zero());
camera.rotation = std::f32::consts::FRAC_PI_2;
let proj_rotated = camera.project(Vec2::zero());
let unproj_rotated = camera.unproject(proj_rotated);
assert!(proj_rotated.x + 16.0 <= 0.001);
assert!(proj_rotated.y - 48.0 <= 0.001);
assert!(unproj_rotated.x.abs() <= 0.001);
assert!(unproj_rotated.y.abs() <= 0.001);
}
#[test]
fn validate_camera_visible_rect() {
let mut camera = Camera::new(800.0, 600.0);
// Camera is centered on 0.0 / 0.0 by default
assert_eq!(
camera.visible_rect(),
Rectangle {
x: -400.0,
y: -300.0,
width: 800.0,
height: 600.0
}
);
// Zooming in will reduce the visible rect size and x/y position
camera.scale.x = 2.0;
camera.scale.y = 4.0;
assert_eq!(
camera.visible_rect(),
Rectangle {
x: -200.0,
y: -75.0,
width: 400.0,
height: 150.0
}
);
// Moving the camera will simply move the x/y position
camera.position = Vec2::new(-100.0, 100.0);
assert_eq!(
camera.visible_rect(),
Rectangle {
x: -300.0,
y: 25.0,
width: 400.0,
height: 150.0
}
);
// Rotating the camera by 0.5 * pi will rotate the rectangle by 90 degrees,
// so the width and height will be swapped
camera.rotation = std::f32::consts::FRAC_PI_2;
// We need to manually compare this to a small value because of rounding errors
let rect = camera.visible_rect();
assert!(rect.x + -175.0 < 0.001);
assert!(rect.y + 100.0 < 0.001);
assert!(rect.width - 150.0 < 0.001);
assert!(rect.height - 400.0 < 0.001);
}
}