Use p_cam_projection.get_endpoints() to calculate the viewport location

Fixes #104193

In OpenXR the viewport location is not centered on the transform origin

Author: jamie-pate

core/math/projection.cpp

@@ -433,6 +433,17 @@ Vector2 Projection::get_far_plane_half_extents() const {
 	return Vector2(w / columns[0][0], w / columns[1][1]);
 }
 
+bool Projection::get_viewport_endpoints(Vector3 &p_bottom_left, Vector3 &p_top_right) const {
+	// get all 6 planes even though we only need 5
+	Vector<Plane> planes = get_projection_planes(Transform3D());
+	Plane near = planes[PLANE_NEAR];
+	bool res = near.intersect_3(planes[PLANE_BOTTOM], planes[PLANE_LEFT], &p_bottom_left);
+	ERR_FAIL_COND_V(!res, false);
+	res = near.intersect_3(planes[PLANE_TOP], planes[PLANE_RIGHT], &p_top_right);
+	ERR_FAIL_COND_V(!res, false);
+	return true;
+}
+
 bool Projection::get_endpoints(const Transform3D &p_transform, Vector3 *p_8points) const {
 	Vector<Plane> planes = get_projection_planes(Transform3D());
 	const Planes intersections[8][3] = {

core/math/projection.h

@@ -108,6 +108,7 @@ struct [[nodiscard]] Projection {
 	Vector<Plane> get_projection_planes(const Transform3D &p_transform) const;
 
 	bool get_endpoints(const Transform3D &p_transform, Vector3 *p_8points) const;
+	bool get_viewport_endpoints(Vector3 &p_top_left, Vector3 &p_bottom_right) const;
 	Vector2 get_viewport_half_extents() const;
 	Vector2 get_far_plane_half_extents() const;
 

modules/raycast/raycast_occlusion_cull.cpp

@@ -525,14 +525,14 @@ void RaycastOcclusionCull::buffer_set_size(RID p_buffer, const Vector2i &p_size)
 	buffers[p_buffer].resize(p_size);
 }
 
-Vector2 RaycastOcclusionCull::_jitter_half_extents(const Vector2 &p_half_extents, const Size2i &p_viewport_size) {
+Vector2 RaycastOcclusionCull::_get_jitter(const Vector2 &p_half_extents, const Size2i &p_viewport_size) {
 	if (!_jitter_enabled) {
-		return p_half_extents;
+		return Vector2();
 	}
 
 	// Prevent divide by zero when using NULL viewport.
 	if ((p_viewport_size.x <= 0) || (p_viewport_size.y <= 0)) {
-		return p_half_extents;
+		return Vector2();
 	}
 
 	int32_t frame = Engine::get_singleton()->get_frames_drawn();
@@ -578,7 +578,7 @@ Vector2 RaycastOcclusionCull::_jitter_half_extents(const Vector2 &p_half_extents
 	// False shown can lower percentage that are occluded, and therefore performance.
 	jitter *= 0.66f;
 
-	return p_half_extents + jitter;
+	return jitter;
 }
 
 void RaycastOcclusionCull::buffer_update(RID p_buffer, const Transform3D &p_cam_transform, const Projection &p_cam_projection, bool p_cam_orthogonal) {
@@ -594,10 +594,14 @@ void RaycastOcclusionCull::buffer_update(RID p_buffer, const Transform3D &p_cam_
 
 	Scenario &scenario = scenarios[buffer.scenario_rid];
 	scenario.update();
-
-	Vector2 viewport_half = p_cam_projection.get_viewport_half_extents();
-	Vector2 jitter_viewport_half = _jitter_half_extents(viewport_half, buffer.get_occlusion_buffer_size());
-	Vector3 near_bottom_left = Vector3(-jitter_viewport_half.x, -jitter_viewport_half.y, -p_cam_projection.get_z_near());
+	Vector3 near_top_right;
+	Vector3 near_bottom_left;
+	p_cam_projection.get_viewport_endpoints(near_bottom_left, near_top_right);
+	Vector3 viewport_extents = near_bottom_left - near_top_right;
+	Vector2 viewport_half = Vector2(viewport_extents.x, viewport_extents.y).abs() * 0.5;
+	Vector2 jitter = _get_jitter(viewport_half, buffer.get_occlusion_buffer_size());
+
+	near_bottom_left += Vector3(jitter.x, jitter.y, 0);
 
 	buffer.update_camera_rays(p_cam_transform, near_bottom_left, 2 * viewport_half, p_cam_projection.get_z_far(), p_cam_orthogonal);
 

modules/raycast/raycast_occlusion_cull.h

@@ -161,7 +161,7 @@ class RaycastOcclusionCull : public RendererSceneOcclusionCull {
 	bool _jitter_enabled = false;
 
 	void _init_embree();
-	Vector2 _jitter_half_extents(const Vector2 &p_half_extents, const Size2i &p_viewport_size);
+	Vector2 _get_jitter(const Vector2 &p_half_extents, const Size2i &p_viewport_size);
 
 public:
 	virtual bool is_occluder(RID p_rid) override;