diff options
Diffstat (limited to 'src/crt.zig')
| -rw-r--r-- | src/crt.zig | 43 |
1 files changed, 0 insertions, 43 deletions
diff --git a/src/crt.zig b/src/crt.zig deleted file mode 100644 index 9cf81593..00000000 --- a/src/crt.zig +++ /dev/null @@ -1,43 +0,0 @@ -//! The Crt builtin's screen geometry, shared between the gui shell's input -//! mapping and its shader: crt.frag.glsl shows the scene point -//! uv' = cc*(1 + barrel*r2) at screen point cc, so a physical mouse position -//! must pass through the SAME forward transform before it becomes a cell. -//! Pure std, so the unit-test step can pin it against the shader formula. - -const std = @import("std"); - -/// MUST match BARREL in shaders/crt.frag.glsl -pub const barrel: f32 = 0.012; - -pub const Point = struct { x: f32, y: f32 }; - -/// physical window pixels -> the scene pixels the shader displays there, -/// clamped to the window. The shader's phosphor quantization and chromatic -/// offset displace at most a few pixels — well under a cell — and are -/// ignored here. -pub fn map(x: f32, y: f32, w: f32, h: f32) Point { - const ccx = x / w * 2.0 - 1.0; - const ccy = y / h * 2.0 - 1.0; - const s = 1.0 + barrel * (ccx * ccx + ccy * ccy); - return .{ - .x = std.math.clamp((ccx * s + 1.0) * 0.5 * w, 0, w - 1), - .y = std.math.clamp((ccy * s + 1.0) * 0.5 * h, 0, h - 1), - }; -} - -test "map matches the shader's barrel formula" { - // center is a fixed point - try std.testing.expectApproxEqAbs(@as(f32, 500), map(500, 250, 1000, 500).x, 0.001); - try std.testing.expectApproxEqAbs(@as(f32, 250), map(500, 250, 1000, 500).y, 0.001); - // corners: cc=(±1,±1), r2=2, scale 1.024 pushes past the tube -> clamped - try std.testing.expectEqual(@as(f32, 0), map(0, 0, 1000, 500).x); - try std.testing.expectEqual(@as(f32, 0), map(0, 0, 1000, 500).y); - try std.testing.expectEqual(@as(f32, 999), map(1000, 500, 1000, 500).x); - try std.testing.expectEqual(@as(f32, 499), map(1000, 500, 1000, 500).y); - // (100,100) of 1000x500: cc=(-0.8,-0.6), r2=1.0, s=1.012 -> - // cc'=(-0.8096,-0.6072) -> (95.2, 98.2) - try std.testing.expectApproxEqAbs(@as(f32, 95.2), map(100, 100, 1000, 500).x, 0.01); - try std.testing.expectApproxEqAbs(@as(f32, 98.2), map(100, 100, 1000, 500).y, 0.01); - // (900,250): cc=(0.8,0), r2=0.64, s=1.00768 -> x'=903.072 - try std.testing.expectApproxEqAbs(@as(f32, 903.072), map(900, 250, 1000, 500).x, 0.01); -} |
