Match wrist mount geometry to VR Workspace watch panel

src/mount.cpp

@@ -62,19 +62,31 @@ std::optional<Matrix34> world_mount_pose(const Matrix34& hmd) {
     return pose;
 }
 
-Matrix34 relative_mount_pose(Mount mount) {
+Matrix34 relative_mount_pose(Mount mount, const WristPlacement& wrist) {
     auto pose = identity;
     switch (mount) {
     case Mount::Head: pose[1][3] = -0.16f; pose[2][3] = -1.05f; break;
-    case Mount::LeftWrist: pose[0][3] = 0.13f; pose[1][3] = 0.12f; pose[2][3] = -0.18f; break;
-    case Mount::RightWrist: pose[0][3] = -0.13f; pose[1][3] = 0.12f; pose[2][3] = -0.18f; break;
+    case Mount::LeftWrist: case Mount::RightWrist: {
+        // VR Workspace's fallback wrist frame maps +Y toward fingers (-Z of
+        // controller), +Z out of the back of the hand (+Y of controller).
+        // Its HUD has right=fingers, up=back of hand, front=right x up.
+        // The 0.089 m Z is the 0.054 m wrist calibration plus 0.035 m
+        // backward from the fingers. Y also accounts for the HUD canvas's
+        // bottom anchor: .12 m wrist lift + .09 m anchor - ~.03 m panel center.
+        const float angle = wrist.roll_degrees * (std::acos(-1.f) / 180.f);
+        const float c = std::cos(angle), s = std::sin(angle);
+        pose[0] = {0.f, s, c, c * wrist.x + s * wrist.y};
+        pose[1] = {0.f, c, -s, -s * wrist.x + c * wrist.y};
+        pose[2] = {-1.f, 0.f, 0.f, wrist.z};
+        break;
+    }
     case Mount::World: break;
     }
     return pose;
 }
 
-float mount_width(Mount mount) {
-    return mount == Mount::LeftWrist || mount == Mount::RightWrist ? 0.42f : 0.85f;
+float mount_width(Mount mount, const WristPlacement& wrist) {
+    return mount == Mount::LeftWrist || mount == Mount::RightWrist ? wrist.width : 0.85f;
 }
 
 std::filesystem::path default_mount_settings_path() {

src/mount.hpp

@@ -15,12 +15,20 @@ std::optional<Mount> parse_mount(std::string_view name);
 // Row-major 3x4 affine transform (OpenVR axes: +Y up, -Z forward).
 using Matrix34 = std::array<std::array<float, 4>, 3>;
 
+// Controller-local watch placement. Defaults follow VR Workspace's fallback
+// wrist calibration and HUD pose (not its avatar-specific calibration).
+struct WristPlacement {
+    float x = 0.f, y = 0.18f, z = 0.089f; // meters in controller coordinates
+    float width = 0.30f; // meters
+    float roll_degrees = 0.f; // about controller -Z before placing the panel
+};
+
 // World-space, yaw-only pose in front of the HMD, upright and facing the viewer.
 // Invalid/nonfinite HMD transforms or a vanishing horizontal forward return nullopt.
 std::optional<Matrix34> world_mount_pose(const Matrix34& hmd);
 // Device-relative transform; World has no relative anchor and returns identity.
-Matrix34 relative_mount_pose(Mount mount);
-float mount_width(Mount mount);
+Matrix34 relative_mount_pose(Mount mount, const WristPlacement& wrist = {});
+float mount_width(Mount mount, const WristPlacement& wrist = {});
 
 // Empty when neither XDG_CONFIG_HOME nor HOME specifies an absolute base.
 std::filesystem::path default_mount_settings_path();

tests/mount_test.cpp

@@ -60,16 +60,25 @@ int main() {
     CHECK(!parse_mount("")); CHECK(!parse_mount("world extra"));
 
     CHECK(near(mount_width(Mount::World), .85f)); CHECK(near(mount_width(Mount::Head), .85f));
-    CHECK(near(mount_width(Mount::LeftWrist), .42f)); CHECK(near(mount_width(Mount::RightWrist), .42f));
+    CHECK(near(mount_width(Mount::LeftWrist), .30f)); CHECK(near(mount_width(Mount::RightWrist), .30f));
     CHECK(relative_mount_pose(Mount::World) == identity);
     const auto head = relative_mount_pose(Mount::Head);
     check_basis(head, 1, 0, 0, 1);
     CHECK(near(head[0][3], 0)); CHECK(near(head[1][3], -.16f)); CHECK(near(head[2][3], -1.05f));
     const auto left = relative_mount_pose(Mount::LeftWrist), right = relative_mount_pose(Mount::RightWrist);
-    check_basis(left, 1, 0, 0, 1); check_basis(right, 1, 0, 0, 1);
-    CHECK(near(left[0][3], .13f)); CHECK(near(right[0][3], -.13f));
-    CHECK(near(left[1][3], .12f)); CHECK(near(right[1][3], .12f));
-    CHECK(near(left[2][3], -.18f)); CHECK(near(right[2][3], -.18f));
+    CHECK(left == right); // VR Workspace fallback calibration uses the same controller-local axes for both hands.
+    CHECK(near(left[0][0], 0)); CHECK(near(left[1][0], 0)); CHECK(near(left[2][0], -1));
+    CHECK(near(left[0][1], 0)); CHECK(near(left[1][1], 1)); CHECK(near(left[2][1], 0));
+    CHECK(near(left[0][2], 1)); CHECK(near(left[1][2], 0)); CHECK(near(left[2][2], 0));
+    CHECK(near(left[0][3], 0)); CHECK(near(left[1][3], .18f)); CHECK(near(left[2][3], .089f));
+    WristPlacement tuned{.02f, .1f, .07f, .25f, 90.f};
+    const auto rotated = relative_mount_pose(Mount::RightWrist, tuned);
+    CHECK(near(rotated[0][1], 1)); CHECK(near(rotated[1][1], 0));
+    CHECK(near(rotated[0][2], 0)); CHECK(near(rotated[1][2], -1));
+    CHECK(near(rotated[0][3], .1f)); CHECK(near(rotated[1][3], -.02f));
+    CHECK(near(rotated[2][3], .07f)); CHECK(near(mount_width(Mount::RightWrist, tuned), .25f));
+    CHECK(relative_mount_pose(Mount::Head, tuned) == head);
+    CHECK(near(mount_width(Mount::World, tuned), .85f));
 
     auto hmd = identity;
     hmd[0][3] = 2; hmd[1][3] = 1.7f; hmd[2][3] = 3;