1 files changed, 22 insertions, 0 deletions
diff --git a/src/geom.zig b/src/geom.zig
index 910f355..96add58 100644
--- a/src/geom.zig
+++ b/src/geom.zig
@@ -18,6 +18,7 @@
 // along with Black Shades.  If not, see <https://www.gnu.org/licenses/>.
 
 const Child = std.meta.Child;
+const degreesToRadians = std.math.degreesToRadians;
 const std = @import("std");
 
 const c = @import("cimport.zig");
@@ -39,6 +40,11 @@ fn norm(v: anytype) Child(@TypeOf(v)) {
     return @sqrt(dot(v, v));
 }
 
+export fn len(v: XYZ) f32 {
+    const u = @bitCast(@Vector(3, f32), v);
+    return norm(u);
+}
+
 const XYZ = extern struct { x: f32, y: f32, z: f32 };
 
 export fn crossProduct(u: XYZ, v: XYZ) XYZ {
@@ -61,6 +67,22 @@ export fn reflect(v: XYZ, n: XYZ) XYZ {
     return @bitCast(XYZ, u - m * @splat(3, dot(u, m) * 2));
 }
 
+fn rotate2d(i: *f32, j: *f32, a: f32) void {
+    if (a == 0) return;
+    const x = i.*;
+    const y = j.*;
+    i.* = x * @cos(a) - y * @sin(a);
+    j.* = x * @sin(a) + y * @cos(a);
+}
+
+export fn rotate(v: XYZ, deg_x: f32, deg_y: f32, deg_z: f32) XYZ {
+    var u = v;
+    rotate2d(&u.z, &u.x, degreesToRadians(f32, deg_y));
+    rotate2d(&u.x, &u.y, degreesToRadians(f32, deg_z));
+    rotate2d(&u.y, &u.z, degreesToRadians(f32, deg_x));
+    return u;
+}
+
 export fn segmentIntersectsSphere(a: XYZ, b: XYZ, j: XYZ, r: f32) bool {
     // FIXME: call directly with vectors
     const p = @bitCast(@Vector(3, f32), a);