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Fix bugs in determinant and inverse

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This commit is contained in:
Alex Selimov 2026-08-20 00:01:43 -04:00
parent 8ab8af992a
commit 6332e3d770
1 changed files with 17 additions and 17 deletions
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34
src/vec3.zig
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@ -90,7 +90,7 @@ pub fn mat3Mul(a: Mat3F64, b: Mat3F64) Mat3F64 {
pub fn mat3Det(a: Mat3F64) f64 { pub fn mat3Det(a: Mat3F64) f64 {
return a.row1.x() * (a.row2.y() * a.row3.z() - a.row2.z() * a.row3.y()) - return a.row1.x() * (a.row2.y() * a.row3.z() - a.row2.z() * a.row3.y()) -
a.row1.y() * (a.row2.x() * a.row3.z() - a.row2.z() * a.row3.x()) + a.row1.y() * (a.row2.x() * a.row3.z() - a.row2.z() * a.row3.x()) +
a.row1.y() * (a.row2.x() * a.row3.y() - a.row2.y() * a.row3.x()); a.row1.z() * (a.row2.x() * a.row3.y() - a.row2.y() * a.row3.x());
} }
pub fn mat3Inv(a: Mat3F64) Mat3F64 { pub fn mat3Inv(a: Mat3F64) Mat3F64 {
@ -105,7 +105,7 @@ pub fn mat3Inv(a: Mat3F64) Mat3F64 {
); );
const row2 = vec3Scale( const row2 = vec3Scale(
.init( .init(
a.row2.z() * a.row3.x() + a.row2.x() * a.row3.z(), a.row2.z() * a.row3.x() - a.row2.x() * a.row3.z(),
a.row1.x() * a.row3.z() - a.row1.z() * a.row3.x(), a.row1.x() * a.row3.z() - a.row1.z() * a.row3.x(),
a.row1.z() * a.row2.x() - a.row1.x() * a.row2.z(), a.row1.z() * a.row2.x() - a.row1.x() * a.row2.z(),
), ),
@ -113,7 +113,7 @@ pub fn mat3Inv(a: Mat3F64) Mat3F64 {
); );
const row3 = vec3Scale( const row3 = vec3Scale(
.init( .init(
a.row2.x() * a.row3.y() + a.row2.y() * a.row3.x(), a.row2.x() * a.row3.y() - a.row2.y() * a.row3.x(),
a.row1.y() * a.row3.x() - a.row1.x() * a.row3.y(), a.row1.y() * a.row3.x() - a.row1.x() * a.row3.y(),
a.row1.x() * a.row2.y() - a.row1.y() * a.row2.x(), a.row1.x() * a.row2.y() - a.row1.y() * a.row2.x(),
), ),
@ -321,30 +321,30 @@ test "Mat3 mul works" {
test "mat determinant works" { test "mat determinant works" {
const a: Mat3F64 = .{ const a: Mat3F64 = .{
.row1 = Vec3F64.init(1, 2, 3), .row1 = Vec3F64.init(1, 2, 3),
.row2 = Vec3F64.init(0, 1, 5), .row2 = Vec3F64.init(4, 1, 5),
.row3 = Vec3F64.init(0, 0, 9), .row3 = Vec3F64.init(3, 1, 9),
}; };
try std.testing.expectApproxEqAbs(9, mat3Det(a), 1e-12); try std.testing.expectApproxEqAbs(-35, mat3Det(a), 1e-12);
} }
test "mat inverse works" { test "mat inverse works" {
const a: Mat3F64 = .{ const a: Mat3F64 = .{
.row1 = Vec3F64.init(1, 2, 3), .row1 = Vec3F64.init(1, 2, 3),
.row2 = Vec3F64.init(0, 1, 5), .row2 = Vec3F64.init(4, 1, 5),
.row3 = Vec3F64.init(0, 0, 9), .row3 = Vec3F64.init(3, 1, 9),
}; };
const ainv = mat3Inv(a); const ainv = mat3Inv(a);
try std.testing.expectApproxEqAbs(1, ainv.row1.x(), 1e-12); try std.testing.expectApproxEqAbs(-4.0 / 35.0, ainv.row1.x(), 1e-12);
try std.testing.expectApproxEqAbs(-2, ainv.row1.y(), 1e-12); try std.testing.expectApproxEqAbs(3.0 / 7.0, ainv.row1.y(), 1e-12);
try std.testing.expectApproxEqAbs(7.0 / 9.0, ainv.row1.z(), 1e-12); try std.testing.expectApproxEqAbs(-1.0 / 5.0, ainv.row1.z(), 1e-12);
try std.testing.expectApproxEqAbs(0, ainv.row2.x(), 1e-12); try std.testing.expectApproxEqAbs(3.0 / 5.0, ainv.row2.x(), 1e-12);
try std.testing.expectApproxEqAbs(1, ainv.row2.y(), 1e-12); try std.testing.expectApproxEqAbs(0, ainv.row2.y(), 1e-12);
try std.testing.expectApproxEqAbs(-5.0 / 9.0, ainv.row2.z(), 1e-12); try std.testing.expectApproxEqAbs(-1.0 / 5.0, ainv.row2.z(), 1e-12);
try std.testing.expectApproxEqAbs(0, ainv.row3.x(), 1e-12); try std.testing.expectApproxEqAbs(-1.0 / 35.0, ainv.row3.x(), 1e-12);
try std.testing.expectApproxEqAbs(0, ainv.row3.y(), 1e-12); try std.testing.expectApproxEqAbs(-1.0 / 7.0, ainv.row3.y(), 1e-12);
try std.testing.expectApproxEqAbs(1.0 / 9.0, ainv.row3.z(), 1e-12); try std.testing.expectApproxEqAbs(1.0 / 5.0, ainv.row3.z(), 1e-12);
} }
test "vec3 mul mat3 works" { test "vec3 mul mat3 works" {
const b: Mat3F64 = .{ const b: Mat3F64 = .{