ROTATION.md

Rotation

Challenge:

Given the Bhj1.mandart inputs, the SwiftUI MandArt program shows the needle pointing to the left. But in the Rust WASM version, the needle is pointing up - 90 degrees off.

Source: get_grid_from_shape_inputs.rs

1. Coordinate System Differences

• SwiftUI uses a coordinate system where the origin (0,0) is at the top-left corner of the view, with the y-axis increasing downward.

• Rust (Canvas/WebGL) typically uses a coordinate system where the origin (0,0) is at the bottom-left corner, with the y-axis increasing upward.

2. Angle Interpretation Difference

• SwiftUI rotations are often measured clockwise from the top.
• Rust/WebGL usually measure counterclockwise from the right or left.

Corrected Theta in Rust

let corrected_theta = -theta + std::f64::consts::FRAC_PI_2;

Also in source file

Why is theta only mentioned in > 3 power?

/// Computes complex power for Mandelbrot iterations. fn complex_pow(base_x: f64, base_y: f64, power_real: i32) -> (f64, f64) { if power_real == 2 { let x_temp = base_x * base_x - base_y * base_y; let new_y = 2.0 * base_x * base_y; (x_temp, new_y) } else if power_real == 3 { let x_squared = base_x * base_x; let y_squared = base_y * base_y;

    let x_temp = (x_squared - 3.0 * y_squared) * base_x;
    let new_y = (3.0 * x_squared - y_squared) * base_y;
    (x_temp, new_y)
} else {
    let r = (base_x * base_x + base_y * base_y).sqrt();
    let theta = base_y.atan2(base_x);
    let new_r = r.powi(power_real);
    let new_theta = (power_real as f64) * theta;

    let new_x = new_r * new_theta.cos();
    let new_y = new_r * new_theta.sin();
    (new_x, new_y)
}

}