Add `intersects_ray()` method to `OpenXRCompositionLayer`

1 files changed, 51 insertions, 0 deletions

diff --git a/modules/openxr/scene/openxr_composition_layer_equirect.cpp b/modules/openxr/scene/openxr_composition_layer_equirect.cpp
index c911dbf6ae..d67e71443c 100644
--- a/modules/openxr/scene/openxr_composition_layer_equirect.cpp
+++ b/modules/openxr/scene/openxr_composition_layer_equirect.cpp
@@ -207,3 +207,54 @@ void OpenXRCompositionLayerEquirect::set_fallback_segments(uint32_t p_fallback_s
 uint32_t OpenXRCompositionLayerEquirect::get_fallback_segments() const {
 	return fallback_segments;
 }
+
+Vector2 OpenXRCompositionLayerEquirect::intersects_ray(const Vector3 &p_origin, const Vector3 &p_direction) const {
+	Transform3D equirect_transform = get_global_transform();
+
+	Vector3 offset = p_origin - equirect_transform.origin;
+	float a = p_direction.dot(p_direction);
+	float b = 2.0 * offset.dot(p_direction);
+	float c = offset.dot(offset) - (radius * radius);
+
+	float discriminant = b * b - 4.0 * a * c;
+	if (discriminant < 0.0) {
+		return Vector2(-1.0, -1.0);
+	}
+
+	float t0 = (-b - Math::sqrt(discriminant)) / (2.0 * a);
+	float t1 = (-b + Math::sqrt(discriminant)) / (2.0 * a);
+	float t = MAX(t0, t1);
+
+	if (t < 0.0) {
+		return Vector2(-1.0, -1.0);
+	}
+	Vector3 intersection = p_origin + p_direction * t;
+
+	Basis correction = equirect_transform.basis.inverse();
+	correction.rotate(Vector3(0.0, 1.0, 0.0), -Math_PI / 2.0);
+	Vector3 relative_point = correction.xform(intersection - equirect_transform.origin);
+
+	float horizontal_intersection_angle = Math::atan2(relative_point.z, relative_point.x);
+	if (Math::abs(horizontal_intersection_angle) > central_horizontal_angle / 2.0) {
+		return Vector2(-1.0, -1.0);
+	}
+
+	float vertical_intersection_angle = Math::acos(relative_point.y / radius) - (Math_PI / 2.0);
+	if (vertical_intersection_angle < 0) {
+		if (Math::abs(vertical_intersection_angle) > upper_vertical_angle) {
+			return Vector2(-1.0, -1.0);
+		}
+	} else if (vertical_intersection_angle > lower_vertical_angle) {
+		return Vector2(-1.0, -1.0);
+	}
+
+	// Re-center the intersection angle if the vertical angle is uneven between upper and lower.
+	if (upper_vertical_angle != lower_vertical_angle) {
+		vertical_intersection_angle -= (-upper_vertical_angle + lower_vertical_angle) / 2.0;
+	}
+
+	float u = 0.5 + (horizontal_intersection_angle / central_horizontal_angle);
+	float v = 0.5 + (vertical_intersection_angle / (upper_vertical_angle + lower_vertical_angle));
+
+	return Vector2(u, v);
+}