From 9e660475a7f54978aab195f8ef55d9fa1ad47299 Mon Sep 17 00:00:00 2001
From: PouleyKetchoupp <pouleyketchoup@gmail.com>
Date: Thu, 14 Jan 2021 15:52:01 -0700
Subject: [PATCH] Improve Raycast3D render debug

Fix Raycast3D node render debug not showing in editor camera preview.

Use dynamic mesh update to change the ray on-the-fly without too much
extra cost when collision debug is enabled.

Fixes #43571
---
 scene/3d/ray_cast_3d.cpp | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/scene/3d/ray_cast_3d.cpp b/scene/3d/ray_cast_3d.cpp
index 59b59c71637..0b7c15a023a 100644
--- a/scene/3d/ray_cast_3d.cpp
+++ b/scene/3d/ray_cast_3d.cpp
@@ -148,14 +148,14 @@ void RayCast3D::_notification(int p_what) {
 		case NOTIFICATION_ENTER_TREE: {
 			if (enabled && !Engine::get_singleton()->is_editor_hint()) {
 				set_physics_process_internal(true);
-
-				if (get_tree()->is_debugging_collisions_hint()) {
-					_update_debug_shape();
-				}
 			} else {
 				set_physics_process_internal(false);
 			}
 
+			if (get_tree()->is_debugging_collisions_hint()) {
+				_update_debug_shape();
+			}
+
 			if (Object::cast_to<CollisionObject3D>(get_parent())) {
 				if (exclude_parent_body) {
 					exclude.insert(Object::cast_to<CollisionObject3D>(get_parent())->get_rid());
@@ -348,23 +348,32 @@ void RayCast3D::_update_debug_shape() {
 	}
 
 	MeshInstance3D *mi = static_cast<MeshInstance3D *>(debug_shape);
-	if (!mi->get_mesh().is_valid()) {
+	Ref<ArrayMesh> mesh = mi->get_mesh();
+	if (!mesh.is_valid()) {
 		return;
 	}
 
-	Ref<ArrayMesh> mesh = mi->get_mesh();
-	mesh->clear_surfaces();
-
-	Array a;
-	a.resize(Mesh::ARRAY_MAX);
-
 	Vector<Vector3> verts;
 	verts.push_back(Vector3());
 	verts.push_back(target_position);
-	a[Mesh::ARRAY_VERTEX] = verts;
 
-	mesh->add_surface_from_arrays(Mesh::PRIMITIVE_LINES, a);
-	mesh->surface_set_material(0, debug_material);
+	if (mesh->get_surface_count() == 0) {
+		Array a;
+		a.resize(Mesh::ARRAY_MAX);
+		a[Mesh::ARRAY_VERTEX] = verts;
+
+		uint32_t flags = Mesh::ARRAY_FLAG_USE_DYNAMIC_UPDATE;
+
+		mesh->add_surface_from_arrays(Mesh::PRIMITIVE_LINES, a, Array(), Dictionary(), flags);
+		mesh->surface_set_material(0, debug_material);
+	} else {
+		Vector<uint8_t> byte_array;
+		int array_size = sizeof(Vector3) * verts.size();
+		byte_array.resize(array_size);
+		copymem(byte_array.ptrw(), verts.ptr(), array_size);
+
+		RS::get_singleton()->mesh_surface_update_region(mesh->get_rid(), 0, 0, byte_array);
+	}
 }
 
 void RayCast3D::_clear_debug_shape() {