1 files changed, 58 insertions, 0 deletions
diff --git a/src/math.zig b/src/math.zig
new file mode 100644
index 0000000..4666cfc
--- /dev/null
+++ b/src/math.zig
@@ -0,0 +1,58 @@
+usingnamespace @import("xrvk.zig");
+const glm = @import("glm");
+const math = @import("std").math;
+
+pub fn vec2vec(v: xr.Vector3f) glm.Vec3 {
+    return glm.Vec3.init([_]f32{ v.x, v.y, v.z });
+}
+
+pub fn quat2mat(q: xr.Quaternionf) glm.Mat4 {
+    const x = -q.x;
+    const y = -q.y;
+    const z = -q.z;
+    const w = q.w;
+    const x2 = q.x * q.x;
+    const y2 = q.y * q.y;
+    const z2 = q.z * q.z;
+
+    // zig fmt: off
+    return glm.Mat4.init([_][4]f32{
+        [_]f32{ 1 - 2 * y2 - 2 * z2, 2 * x * y - 2 * z * w, 2 * x * z + 2 * y * w, 0 },
+        [_]f32{ 2 * x * y + 2 * z * w, 1 - 2 * x2 - 2 * z2, 2 * y * z - 2 * x * w, 0 },
+        [_]f32{ 2 * x * z - 2 * y * w, 2 * y * z + 2 * x * w, 1 - 2 * x2 - 2 * y2, 0 },
+        [_]f32{ 0, 0, 0, 1 },
+    });
+    // zig fmt: on
+}
+
+pub fn pose2mat(pose: xr.Posef) glm.Mat4 {
+    return glm.translation(vec2vec(pose.position)).mul(quat2mat(pose.orientation));
+}
+
+pub fn pose2matInverse(pose: xr.Posef) glm.Mat4 {
+    var inverse = pose;
+    inverse.orientation.x *= -1;
+    inverse.orientation.y *= -1;
+    inverse.orientation.z *= -1;
+    inverse.position.x *= -1;
+    inverse.position.y *= -1;
+    inverse.position.z *= -1;
+    return quat2mat(inverse.orientation).mul(glm.translation(vec2vec(inverse.position)));
+}
+
+
+pub fn projection(fov: xr.Fovf, near: f32, far: f32) glm.Mat4 {
+    const tanUp = math.tan(fov.angle_up);
+    const tanDown = math.tan(fov.angle_down);
+    const tanLeft = math.tan(fov.angle_left);
+    const tanRight = math.tan(fov.angle_right);
+    const tanW  = tanRight - tanLeft;
+    const tanH  = tanUp - tanDown ;
+
+    return glm.Mat4.init([_][4]f32{
+        [_]f32{ 2 / tanW, 0, 0, 0 },
+        [_]f32{ 0, 2 / tanH, 0, 0 },
+        [_]f32{ (tanRight + tanLeft) / tanW, (tanUp + tanDown) / tanH, -far / (far - near), -1 },
+        [_]f32{ 0, 0, -far * near / (far - near), 0 },
+    });
+}