From 37ef04c9863fda6f635d7006c8d83fc21d681967 Mon Sep 17 00:00:00 2001
From: PouleyKetchoupp <pouleyketchoup@gmail.com>
Date: Thu, 14 Jan 2021 15:51:22 -0700
Subject: [PATCH] Improve Raycast render debug

Fix Raycast 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.cpp | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/scene/3d/ray_cast.cpp b/scene/3d/ray_cast.cpp
index fbe3cd7a3ed..77fd724574f 100644
--- a/scene/3d/ray_cast.cpp
+++ b/scene/3d/ray_cast.cpp
@@ -153,11 +153,13 @@ void RayCast::_notification(int p_what) {
 
 			if (enabled && !Engine::get_singleton()->is_editor_hint()) {
 				set_physics_process_internal(true);
-
-				if (get_tree()->is_debugging_collisions_hint())
-					_update_debug_shape();
-			} else
+			} else {
 				set_physics_process_internal(false);
+			}
+
+			if (get_tree()->is_debugging_collisions_hint()) {
+				_update_debug_shape();
+			}
 
 			if (Object::cast_to<CollisionObject>(get_parent())) {
 				if (exclude_parent_body)
@@ -359,23 +361,32 @@ void RayCast::_update_debug_shape() {
 		_create_debug_shape();
 
 	MeshInstance *mi = static_cast<MeshInstance *>(debug_shape);
-	if (!mi->get_mesh().is_valid())
-		return;
-
 	Ref<ArrayMesh> mesh = mi->get_mesh();
-	if (mesh->get_surface_count() > 0)
-		mesh->surface_remove(0);
-
-	Array a;
-	a.resize(Mesh::ARRAY_MAX);
+	if (!mesh.is_valid())
+		return;
 
 	Vector<Vector3> verts;
 	verts.push_back(Vector3());
 	verts.push_back(cast_to);
-	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(), flags);
+		mesh->surface_set_material(0, debug_material);
+	} else {
+		PoolByteArray byte_array;
+		int array_size = sizeof(Vector3) * verts.size();
+		byte_array.resize(array_size);
+		PoolByteArray::Write w = byte_array.write();
+		copymem(w.ptr(), verts.ptr(), array_size);
+
+		VS::get_singleton()->mesh_surface_update_region(mesh->get_rid(), 0, 0, byte_array);
+	}
 }
 
 void RayCast::_clear_debug_shape() {