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use crate::vector::Vec3;
#[derive(Debug, Clone)]
#[repr(C)]
pub struct Matrix<Value, const ROWS: usize, const COLUMNS: usize>
{
/// Items must be layed out this way for it to work with OpenGL shaders.
items: [[Value; ROWS]; COLUMNS],
}
impl<Value, const ROWS: usize, const COLUMNS: usize> Matrix<Value, ROWS, COLUMNS>
{
pub fn new() -> Self
where
Value: Default + Copy,
{
Self {
items: [[Value::default(); ROWS]; COLUMNS],
}
}
/// Sets the value at the specified cell.
pub fn set_cell(&mut self, row: usize, column: usize, value: Value)
{
self.items[column][row] = value;
}
#[must_use]
pub fn as_ptr(&self) -> *const Value
{
self.items[0].as_ptr()
}
}
impl<const ROWS_COLS: usize> Matrix<f32, ROWS_COLS, ROWS_COLS>
{
/// Creates a new identity matrix.
#[must_use]
pub fn new_identity() -> Self
{
let mut index = 0;
let items = [(); ROWS_COLS].map(|()| {
let mut columns = [0.0; ROWS_COLS];
columns[index] = 1.0;
index += 1;
columns
});
Self { items }
}
}
impl Matrix<f32, 4, 4>
{
pub fn translate(&mut self, translation: &Vec3<f32>)
{
self.set_cell(0, 3, translation.x);
self.set_cell(1, 3, translation.y);
self.set_cell(2, 3, translation.z);
self.set_cell(3, 3, 1.0);
}
pub fn scale(&mut self, scaling: &Vec3<f32>)
{
self.set_cell(0, 0, scaling.x);
self.set_cell(1, 1, scaling.y);
self.set_cell(2, 2, scaling.z);
self.set_cell(3, 3, 1.0);
}
pub fn look_at(&mut self, eye: &Vec3<f32>, target: &Vec3<f32>, up: &Vec3<f32>)
{
let rev_target_direction = (eye - target).normalize();
let camera_right = up.cross(&rev_target_direction).normalize();
let camera_up = rev_target_direction.cross(&camera_right);
self.set_cell(0, 0, camera_right.x);
self.set_cell(0, 1, camera_right.y);
self.set_cell(0, 2, camera_right.z);
self.set_cell(1, 0, camera_up.x);
self.set_cell(1, 1, camera_up.y);
self.set_cell(1, 2, camera_up.z);
self.set_cell(2, 0, rev_target_direction.x);
self.set_cell(2, 1, rev_target_direction.y);
self.set_cell(2, 2, rev_target_direction.z);
// The vector is negated since we want the world to be translated in the opposite
// direction of where we want the camera to move.
let camera_pos = -Vec3 {
x: camera_right.dot(eye),
y: camera_up.dot(eye),
z: rev_target_direction.dot(eye),
};
self.set_cell(0, 3, camera_pos.x);
self.set_cell(1, 3, camera_pos.y);
self.set_cell(2, 3, camera_pos.z);
self.set_cell(3, 3, 1.0);
}
}
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