diff --git a/editor/voxel_graph_editor.cpp b/editor/voxel_graph_editor.cpp
index 0b22bdfd..d635ed05 100644
--- a/editor/voxel_graph_editor.cpp
+++ b/editor/voxel_graph_editor.cpp
@@ -1,6 +1,9 @@
 #include "voxel_graph_editor.h"
 #include "../generators/graph/voxel_generator_graph.h"
 #include "editor/editor_scale.h"
+
+#include <core/core_string_names.h>
+#include <core/os/os.h>
 #include <core/undo_redo.h>
 #include <scene/gui/graph_edit.h>
 #include <scene/gui/label.h>
@@ -8,11 +11,44 @@
 const char *VoxelGraphEditor::SIGNAL_NODE_SELECTED = "node_selected";
 const char *VoxelGraphEditor::SIGNAL_NOTHING_SELECTED = "nothing_selected";
 
+// Shows a 2D slice of the 3D set of values coming from an output port
+class VoxelGraphEditorNodePreview : public VBoxContainer {
+	GDCLASS(VoxelGraphEditorNodePreview, VBoxContainer)
+public:
+	static const int RESOLUTION = 64;
+
+	VoxelGraphEditorNodePreview() {
+		_image.instance();
+		_image->create(RESOLUTION, RESOLUTION, false, Image::FORMAT_L8);
+		_texture.instance();
+		update_texture();
+		_texture_rect = memnew(TextureRect);
+		_texture_rect->set_stretch_mode(TextureRect::STRETCH_SCALE);
+		_texture_rect->set_custom_minimum_size(Vector2(RESOLUTION, RESOLUTION));
+		_texture_rect->set_texture(_texture);
+		add_child(_texture_rect);
+	}
+
+	Ref<Image> get_image() const {
+		return _image;
+	}
+
+	void update_texture() {
+		_texture->create_from_image(_image, 0);
+	}
+
+private:
+	TextureRect *_texture_rect = nullptr;
+	Ref<ImageTexture> _texture;
+	Ref<Image> _image;
+};
+
 // Graph node with a few custom data attached.
 class VoxelGraphEditorNode : public GraphNode {
 	GDCLASS(VoxelGraphEditorNode, GraphNode)
 public:
 	uint32_t node_id = 0;
+	VoxelGraphEditorNodePreview *preview = nullptr;
 };
 
 VoxelGraphEditor::VoxelGraphEditor() {
@@ -43,13 +79,15 @@ void VoxelGraphEditor::set_graph(Ref<VoxelGeneratorGraph> graph) {
 		return;
 	}
 
-	//	if (_graph.is_valid()) {
-	//	}
+	if (_graph.is_valid()) {
+		_graph->disconnect(CoreStringNames::get_singleton()->changed, this, "_on_graph_changed");
+	}
 
 	_graph = graph;
 
-	//	if (_graph.is_valid()) {
-	//	}
+	if (_graph.is_valid()) {
+		_graph->connect(CoreStringNames::get_singleton()->changed, this, "_on_graph_changed");
+	}
 
 	build_gui_from_graph();
 }
@@ -58,6 +96,27 @@ void VoxelGraphEditor::set_undo_redo(UndoRedo *undo_redo) {
 	_undo_redo = undo_redo;
 }
 
+void VoxelGraphEditor::_notification(int p_what) {
+	switch (p_what) {
+		case NOTIFICATION_INTERNAL_PROCESS:
+			_process(get_tree()->get_idle_process_time());
+			break;
+
+		case NOTIFICATION_VISIBILITY_CHANGED:
+			set_process_internal(is_visible());
+			break;
+	}
+}
+
+void VoxelGraphEditor::_process(float delta) {
+	if (_time_before_preview_update > 0.f) {
+		_time_before_preview_update -= delta;
+		if (_time_before_preview_update < 0.f) {
+			update_previews();
+		}
+	}
+}
+
 void VoxelGraphEditor::clear() {
 	_graph_edit->clear_connections();
 	for (int i = 0; i < _graph_edit->get_child_count(); ++i) {
@@ -164,6 +223,11 @@ void VoxelGraphEditor::create_node_gui(uint32_t node_id) {
 		node_view->set_slot(i, has_left, Variant::REAL, port_color, has_right, Variant::REAL, port_color);
 	}
 
+	if (node_type_id == VoxelGeneratorGraph::NODE_SDF_PREVIEW) {
+		node_view->preview = memnew(VoxelGraphEditorNodePreview);
+		node_view->add_child(node_view->preview);
+	}
+
 	_graph_edit->add_child(node_view);
 }
 
@@ -386,6 +450,89 @@ void VoxelGraphEditor::_check_nothing_selected() {
 	}
 }
 
+void VoxelGraphEditor::update_previews() {
+	if (_graph.is_null()) {
+		return;
+	}
+
+	uint64_t time_before = OS::get_singleton()->get_ticks_usec();
+
+	_graph->compile();
+
+	// TODO Use a thread?
+	print_line("Updating previews");
+
+	struct PreviewInfo {
+		VoxelGraphEditorNodePreview *control;
+		uint16_t address;
+		float min_value;
+		float value_scale;
+	};
+
+	std::vector<PreviewInfo> previews;
+	const VoxelGraphRuntime &runtime = _graph->get_runtime();
+
+	for (int i = 0; i < _graph_edit->get_child_count(); ++i) {
+		VoxelGraphEditorNode *node = Object::cast_to<VoxelGraphEditorNode>(_graph_edit->get_child(i));
+		if (node == nullptr || node->preview == nullptr) {
+			continue;
+		}
+		ProgramGraph::PortLocation dst;
+		dst.node_id = node->node_id;
+		dst.port_index = 0;
+		ProgramGraph::PortLocation src;
+		if (!_graph->try_get_connection_to(dst, src)) {
+			// Not connected?
+			continue;
+		}
+		PreviewInfo info;
+		info.control = node->preview;
+		info.address = runtime.get_output_port_address(src);
+		info.min_value = _graph->get_node_param(dst.node_id, 0);
+		const float max_value = _graph->get_node_param(dst.node_id, 1);
+		info.value_scale = 1.f / (max_value - info.min_value);
+		previews.push_back(info);
+	}
+
+	for (size_t i = 0; i < previews.size(); ++i) {
+		previews[i].control->get_image()->lock();
+	}
+
+	for (int iy = 0; iy < VoxelGraphEditorNodePreview::RESOLUTION; ++iy) {
+		for (int ix = 0; ix < VoxelGraphEditorNodePreview::RESOLUTION; ++ix) {
+			{
+				const int x = ix - VoxelGraphEditorNodePreview::RESOLUTION / 2;
+				const int y = (VoxelGraphEditorNodePreview::RESOLUTION - iy) - VoxelGraphEditorNodePreview::RESOLUTION / 2;
+				_graph->generate_single(Vector3i(x, y, 0));
+			}
+
+			for (size_t i = 0; i < previews.size(); ++i) {
+				PreviewInfo &info = previews[i];
+				const float v = runtime.get_memory_value(info.address);
+				const float g = clamp((v - info.min_value) * info.value_scale, 0.f, 1.f);
+				Color c(g, g, g);
+				info.control->get_image()->set_pixel(ix, iy, Color(g, g, g));
+			}
+		}
+	}
+
+	for (size_t i = 0; i < previews.size(); ++i) {
+		previews[i].control->get_image()->unlock();
+		previews[i].control->update_texture();
+	}
+
+	uint64_t time_taken = OS::get_singleton()->get_ticks_usec() - time_before;
+	print_line(String("Previews generated in {0} us").format(varray(time_taken)));
+}
+
+void VoxelGraphEditor::schedule_preview_update() {
+	_time_before_preview_update = 0.5f;
+}
+
+void VoxelGraphEditor::_on_graph_changed() {
+	schedule_preview_update();
+}
+
 void VoxelGraphEditor::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("_on_graph_edit_gui_input", "event"), &VoxelGraphEditor::_on_graph_edit_gui_input);
 	ClassDB::bind_method(D_METHOD("_on_graph_edit_connection_request", "from_node_name", "from_slot", "to_node_name", "to_slot"),
@@ -397,6 +544,8 @@ void VoxelGraphEditor::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("_on_graph_edit_node_unselected"), &VoxelGraphEditor::_on_graph_edit_node_unselected);
 	ClassDB::bind_method(D_METHOD("_on_graph_node_dragged", "from", "to", "id"), &VoxelGraphEditor::_on_graph_node_dragged);
 	ClassDB::bind_method(D_METHOD("_on_context_menu_index_pressed", "idx"), &VoxelGraphEditor::_on_context_menu_index_pressed);
+	ClassDB::bind_method(D_METHOD("_on_graph_changed"), &VoxelGraphEditor::_on_graph_changed);
+
 	ClassDB::bind_method(D_METHOD("_check_nothing_selected"), &VoxelGraphEditor::_check_nothing_selected);
 
 	ClassDB::bind_method(D_METHOD("create_node_gui", "node_id"), &VoxelGraphEditor::create_node_gui);
diff --git a/editor/voxel_graph_editor.h b/editor/voxel_graph_editor.h
index 6bcf3701..543cd5b1 100644
--- a/editor/voxel_graph_editor.h
+++ b/editor/voxel_graph_editor.h
@@ -23,12 +23,18 @@ public:
 	void set_undo_redo(UndoRedo *undo_redo);
 
 private:
+	void _notification(int p_what);
+	void _process(float delta);
+
 	void clear();
 	void build_gui_from_graph();
 	void create_node_gui(uint32_t node_id);
 	void remove_node_gui(StringName gui_node_name);
 	void set_node_position(int id, Vector2 offset);
 
+	void schedule_preview_update();
+	void update_previews();
+
 	void _on_graph_edit_gui_input(Ref<InputEvent> event);
 	void _on_graph_edit_connection_request(String from_node_name, int from_slot, String to_node_name, int to_slot);
 	void _on_graph_edit_disconnection_request(String from_node_name, int from_slot, String to_node_name, int to_slot);
@@ -37,6 +43,7 @@ private:
 	void _on_graph_edit_node_unselected(Node *p_node);
 	void _on_graph_node_dragged(Vector2 from, Vector2 to, int id);
 	void _on_context_menu_index_pressed(int idx);
+	void _on_graph_changed();
 
 	void _check_nothing_selected();
 
@@ -48,6 +55,7 @@ private:
 	UndoRedo *_undo_redo = nullptr;
 	Vector2 _click_position;
 	bool _nothing_selected_check_scheduled = false;
+	float _time_before_preview_update = 0.f;
 };
 
 #endif // VOXEL_GRAPH_EDITOR_H
diff --git a/generators/graph/program_graph.cpp b/generators/graph/program_graph.cpp
index 26a99216..725c05ba 100644
--- a/generators/graph/program_graph.cpp
+++ b/generators/graph/program_graph.cpp
@@ -116,6 +116,7 @@ bool ProgramGraph::can_connect(PortLocation src, PortLocation dst) const {
 		return false;
 	}
 	const Node *dst_node = get_node(dst.node_id);
+	// There can be only one connection from a source to a destination
 	return dst_node->inputs[dst.port_index].connections.size() == 0;
 }
 
diff --git a/generators/graph/voxel_generator_graph.cpp b/generators/graph/voxel_generator_graph.cpp
index 97f76e4e..e344fd98 100644
--- a/generators/graph/voxel_generator_graph.cpp
+++ b/generators/graph/voxel_generator_graph.cpp
@@ -2,6 +2,8 @@
 #include "../../util/profiling_clock.h"
 #include "voxel_graph_node_db.h"
 
+#include <core/core_string_names.h>
+
 VoxelGeneratorGraph::VoxelGeneratorGraph() {
 	clear();
 	clear_bounds();
@@ -47,6 +49,7 @@ ProgramGraph::Node *VoxelGeneratorGraph::create_node_internal(NodeTypeID type_id
 
 void VoxelGeneratorGraph::remove_node(uint32_t node_id) {
 	_graph.remove_node(node_id);
+	emit_changed();
 }
 
 bool VoxelGeneratorGraph::can_connect(uint32_t src_node_id, uint32_t src_port_index, uint32_t dst_node_id, uint32_t dst_port_index) const {
@@ -59,12 +62,14 @@ void VoxelGeneratorGraph::add_connection(uint32_t src_node_id, uint32_t src_port
 	_graph.connect(
 			ProgramGraph::PortLocation{ src_node_id, src_port_index },
 			ProgramGraph::PortLocation{ dst_node_id, dst_port_index });
+	emit_changed();
 }
 
 void VoxelGeneratorGraph::remove_connection(uint32_t src_node_id, uint32_t src_port_index, uint32_t dst_node_id, uint32_t dst_port_index) {
 	_graph.disconnect(
 			ProgramGraph::PortLocation{ src_node_id, src_port_index },
 			ProgramGraph::PortLocation{ dst_node_id, dst_port_index });
+	emit_changed();
 }
 
 void VoxelGeneratorGraph::get_connections(std::vector<ProgramGraph::Connection> &connections) const {
@@ -75,6 +80,18 @@ void VoxelGeneratorGraph::get_connections(std::vector<ProgramGraph::Connection>
 //	_graph.get_connections_from_and_to(connections, node_id);
 //}
 
+bool VoxelGeneratorGraph::try_get_connection_to(ProgramGraph::PortLocation dst, ProgramGraph::PortLocation &out_src) const {
+	const ProgramGraph::Node *node = _graph.get_node(dst.node_id);
+	CRASH_COND(node == nullptr);
+	CRASH_COND(dst.port_index >= node->inputs.size());
+	const ProgramGraph::Port &port = node->inputs[dst.port_index];
+	if (port.connections.size() == 0) {
+		return false;
+	}
+	out_src = port.connections[0];
+	return true;
+}
+
 bool VoxelGeneratorGraph::has_node(uint32_t node_id) const {
 	return _graph.try_get_node(node_id) != nullptr;
 }
@@ -83,7 +100,24 @@ void VoxelGeneratorGraph::set_node_param(uint32_t node_id, uint32_t param_index,
 	ProgramGraph::Node *node = _graph.try_get_node(node_id);
 	ERR_FAIL_COND(node == nullptr);
 	ERR_FAIL_INDEX(param_index, node->params.size());
-	node->params[param_index] = value;
+
+	// TODO Changing sub-resources won't trigger a change signal
+	// It's actually very annoying to setup and keep correct. Needs to be done cautiously.
+
+	// Ref<Resource> res = node->params[param_index];
+	// if (res.is_valid()) {
+	// 	res->disconnect(CoreStringNames::get_singleton()->changed, this, "_on_subresource_changed");
+	// }
+
+	if (node->params[param_index] != value) {
+		node->params[param_index] = value;
+		emit_changed();
+	}
+
+	// res = value;
+	// if (res.is_valid()) {
+	// 	res->connect(CoreStringNames::get_singleton()->changed, this, "_on_subresource_changed");
+	// }
 }
 
 Variant VoxelGeneratorGraph::get_node_param(uint32_t node_id, uint32_t param_index) const {
@@ -104,7 +138,10 @@ void VoxelGeneratorGraph::set_node_default_input(uint32_t node_id, uint32_t inpu
 	ProgramGraph::Node *node = _graph.try_get_node(node_id);
 	ERR_FAIL_COND(node == nullptr);
 	ERR_FAIL_INDEX(input_index, node->default_inputs.size());
-	node->default_inputs[input_index] = value;
+	if (node->default_inputs[input_index] != value) {
+		node->default_inputs[input_index] = value;
+		emit_changed();
+	}
 }
 
 Vector2 VoxelGeneratorGraph::get_node_gui_position(uint32_t node_id) const {
@@ -116,7 +153,11 @@ Vector2 VoxelGeneratorGraph::get_node_gui_position(uint32_t node_id) const {
 void VoxelGeneratorGraph::set_node_gui_position(uint32_t node_id, Vector2 pos) {
 	ProgramGraph::Node *node = _graph.try_get_node(node_id);
 	ERR_FAIL_COND(node == nullptr);
-	node->gui_position = pos;
+	if (node->gui_position != pos) {
+		node->gui_position = pos;
+		// Moving nodes around doesn't functionally change the graph
+		//emit_changed();
+	}
 }
 
 VoxelGeneratorGraph::NodeTypeID VoxelGeneratorGraph::get_node_type_id(uint32_t node_id) const {
@@ -658,6 +699,10 @@ float VoxelGeneratorGraph::_b_generate_single(Vector3 pos) {
 	return generate_single(Vector3i(pos));
 }
 
+// void VoxelGeneratorGraph::_on_subresource_changed() {
+// 	emit_changed();
+// }
+
 void VoxelGeneratorGraph::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("clear"), &VoxelGeneratorGraph::clear);
 	ClassDB::bind_method(D_METHOD("create_node", "type_id", "position", "id"), &VoxelGeneratorGraph::create_node, DEFVAL(ProgramGraph::NULL_ID));
@@ -690,6 +735,8 @@ void VoxelGeneratorGraph::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("_set_graph_data", "data"), &VoxelGeneratorGraph::load_graph_from_variant_data);
 	ClassDB::bind_method(D_METHOD("_get_graph_data"), &VoxelGeneratorGraph::get_graph_as_variant_data);
 
+	// ClassDB::bind_method(D_METHOD("_on_subresource_changed"), &VoxelGeneratorGraph::_on_subresource_changed);
+
 	ADD_PROPERTY(PropertyInfo(Variant::DICTIONARY, "graph_data", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NOEDITOR | PROPERTY_USAGE_INTERNAL),
 			"_set_graph_data", "_get_graph_data");
 
@@ -725,5 +772,6 @@ void VoxelGeneratorGraph::_bind_methods() {
 	BIND_ENUM_CONSTANT(NODE_SDF_BOX);
 	BIND_ENUM_CONSTANT(NODE_SDF_SPHERE);
 	BIND_ENUM_CONSTANT(NODE_SDF_TORUS);
+	BIND_ENUM_CONSTANT(NODE_SDF_PREVIEW);
 	BIND_ENUM_CONSTANT(NODE_TYPE_COUNT);
 }
diff --git a/generators/graph/voxel_generator_graph.h b/generators/graph/voxel_generator_graph.h
index 4159768b..9324054a 100644
--- a/generators/graph/voxel_generator_graph.h
+++ b/generators/graph/voxel_generator_graph.h
@@ -41,6 +41,7 @@ public:
 		NODE_SDF_BOX,
 		NODE_SDF_SPHERE,
 		NODE_SDF_TORUS,
+		NODE_SDF_PREVIEW, // For debugging
 		NODE_TYPE_COUNT
 	};
 
@@ -57,6 +58,7 @@ public:
 	void remove_connection(uint32_t src_node_id, uint32_t src_port_index, uint32_t dst_node_id, uint32_t dst_port_index);
 	void get_connections(std::vector<ProgramGraph::Connection> &connections) const;
 	//void get_connections_from_and_to(std::vector<ProgramGraph::Connection> &connections, uint32_t node_id) const;
+	bool try_get_connection_to(ProgramGraph::PortLocation dst, ProgramGraph::PortLocation &out_src) const;
 
 	bool has_node(uint32_t node_id) const;
 
@@ -91,13 +93,17 @@ public:
 
 	Ref<Resource> duplicate(bool p_subresources) const override;
 
+	// Internal
+
+	const VoxelGraphRuntime &get_runtime() const { return _runtime; }
+	void compile();
+
 	// Debug
 
 	float debug_measure_microseconds_per_voxel();
 	void debug_load_waves_preset();
 
 private:
-	void compile();
 	Interval analyze_range(Vector3i min_pos, Vector3i max_pos);
 
 	ProgramGraph::Node *create_node_internal(NodeTypeID type_id, Vector2 position, uint32_t id);
@@ -118,6 +124,9 @@ private:
 	void _b_set_node_param_null(int node_id, int param_index);
 	float _b_generate_single(Vector3 pos);
 
+	void _on_subresource_changed();
+	void connect_to_subresource_changes();
+
 	static void _bind_methods();
 
 	struct Bounds {
diff --git a/generators/graph/voxel_graph_node_db.cpp b/generators/graph/voxel_graph_node_db.cpp
index 829607ef..86f4953b 100644
--- a/generators/graph/voxel_graph_node_db.cpp
+++ b/generators/graph/voxel_graph_node_db.cpp
@@ -258,6 +258,14 @@ VoxelGraphNodeDB::VoxelGraphNodeDB() {
 		t.inputs.push_back(Port("radius2", 4.f));
 		t.outputs.push_back(Port("sdf"));
 	}
+	{
+		NodeType &t = types[VoxelGeneratorGraph::NODE_SDF_PREVIEW];
+		t.name = "SdfPreview";
+		t.inputs.push_back(Port("value"));
+		t.params.push_back(Param("min_value", Variant::REAL, -1.f));
+		t.params.push_back(Param("max_value", Variant::REAL, 1.f));
+		t.debug_only = true;
+	}
 
 	for (unsigned int i = 0; i < _types.size(); ++i) {
 		NodeType &t = _types[i];
diff --git a/generators/graph/voxel_graph_node_db.h b/generators/graph/voxel_graph_node_db.h
index e0ebabb8..a4535c2b 100644
--- a/generators/graph/voxel_graph_node_db.h
+++ b/generators/graph/voxel_graph_node_db.h
@@ -40,6 +40,8 @@ public:
 
 	struct NodeType {
 		String name;
+		bool debug_only = false;
+		// TODO Category
 		std::vector<Port> inputs;
 		std::vector<Port> outputs;
 		std::vector<Param> params;
diff --git a/generators/graph/voxel_graph_runtime.cpp b/generators/graph/voxel_graph_runtime.cpp
index 47ae68cd..20f65677 100644
--- a/generators/graph/voxel_graph_runtime.cpp
+++ b/generators/graph/voxel_graph_runtime.cpp
@@ -181,15 +181,23 @@ void VoxelGraphRuntime::clear() {
 	_xzy_program_start = 0;
 	_last_x = INT_MAX;
 	_last_z = INT_MAX;
+	_output_port_addresses.clear();
 }
 
 void VoxelGraphRuntime::compile(const ProgramGraph &graph) {
+	_output_port_addresses.clear();
+
 	std::vector<uint32_t> order;
 	std::vector<uint32_t> terminal_nodes;
 
 	graph.find_terminal_nodes(terminal_nodes);
-	// For now only 1 end is supported
-	ERR_FAIL_COND(terminal_nodes.size() != 1);
+
+	// Exclude debug nodes
+	unordered_remove_if(terminal_nodes, [&graph](uint32_t node_id) {
+		const ProgramGraph::Node *node = graph.get_node(node_id);
+		const VoxelGraphNodeDB::NodeType &type = VoxelGraphNodeDB::get_singleton()->get_type(node->type_id);
+		return type.debug_only;
+	});
 
 	graph.find_dependencies(terminal_nodes.back(), order);
 
@@ -271,7 +279,6 @@ void VoxelGraphRuntime::compile(const ProgramGraph &graph) {
 
 	std::vector<uint8_t> &program = _program;
 	const VoxelGraphNodeDB &type_db = *VoxelGraphNodeDB::get_singleton();
-	HashMap<ProgramGraph::PortLocation, uint16_t, ProgramGraph::PortLocationHasher> output_port_addresses;
 	bool has_output = false;
 
 	// Run through each node in order, and turn them into program instructions
@@ -294,19 +301,19 @@ void VoxelGraphRuntime::compile(const ProgramGraph &graph) {
 				CRASH_COND(type.params.size() != 1);
 				uint16_t a = _memory.size();
 				_memory.push_back(node->params[0].operator float());
-				output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = a;
+				_output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = a;
 			} break;
 
 			case VoxelGeneratorGraph::NODE_INPUT_X:
-				output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 0;
+				_output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 0;
 				break;
 
 			case VoxelGeneratorGraph::NODE_INPUT_Y:
-				output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 1;
+				_output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 1;
 				break;
 
 			case VoxelGeneratorGraph::NODE_INPUT_Z:
-				output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 2;
+				_output_port_addresses[ProgramGraph::PortLocation{ node_id, 0 }] = 2;
 				break;
 
 			case VoxelGeneratorGraph::NODE_OUTPUT_SDF:
@@ -337,7 +344,7 @@ void VoxelGraphRuntime::compile(const ProgramGraph &graph) {
 
 					} else {
 						ProgramGraph::PortLocation src_port = node->inputs[j].connections[0];
-						const uint16_t *aptr = output_port_addresses.getptr(src_port);
+						const uint16_t *aptr = _output_port_addresses.getptr(src_port);
 						// Previous node ports must have been registered
 						CRASH_COND(aptr == nullptr);
 						a = *aptr;
@@ -353,7 +360,7 @@ void VoxelGraphRuntime::compile(const ProgramGraph &graph) {
 
 					// This will be used by next nodes
 					const ProgramGraph::PortLocation op{ node_id, static_cast<uint32_t>(j) };
-					output_port_addresses[op] = a;
+					_output_port_addresses[op] = a;
 
 					append(program, a);
 				}
@@ -980,3 +987,14 @@ Interval VoxelGraphRuntime::analyze_range(Vector3i min_pos, Vector3i max_pos) {
 
 	return Interval(min_memory[min_memory.size() - 1], max_memory[max_memory.size() - 1]);
 }
+
+uint16_t VoxelGraphRuntime::get_output_port_address(ProgramGraph::PortLocation port) const {
+	const uint16_t *aptr = _output_port_addresses.getptr(port);
+	ERR_FAIL_COND_V(aptr == nullptr, 0);
+	return *aptr;
+}
+
+float VoxelGraphRuntime::get_memory_value(uint16_t address) const {
+	CRASH_COND(address >= _memory.size());
+	return _memory[address];
+}
diff --git a/generators/graph/voxel_graph_runtime.h b/generators/graph/voxel_graph_runtime.h
index c1523a74..4f27c2b1 100644
--- a/generators/graph/voxel_graph_runtime.h
+++ b/generators/graph/voxel_graph_runtime.h
@@ -15,12 +15,18 @@ public:
 	float generate_single(const Vector3i &position);
 	Interval analyze_range(Vector3i min_pos, Vector3i max_pos);
 
+	// Debugging
+	uint16_t get_output_port_address(ProgramGraph::PortLocation port) const;
+	float get_memory_value(uint16_t address) const;
+
 private:
 	std::vector<uint8_t> _program;
 	std::vector<float> _memory;
 	uint32_t _xzy_program_start;
 	int _last_x;
 	int _last_z;
+
+	HashMap<ProgramGraph::PortLocation, uint16_t, ProgramGraph::PortLocationHasher> _output_port_addresses;
 };
 
 #endif // VOXEL_GRAPH_RUNTIME_H
diff --git a/math/interval.h b/math/interval.h
index 2b672a88..79d2e15a 100644
--- a/math/interval.h
+++ b/math/interval.h
@@ -5,7 +5,6 @@
 
 // For interval arithmetic
 struct Interval {
-
 	// Both inclusive
 	float min;
 	float max;
diff --git a/util/utility.h b/util/utility.h
index f486931c..e1f6cd46 100644
--- a/util/utility.h
+++ b/util/utility.h
@@ -50,6 +50,8 @@ inline void unordered_remove_if(std::vector<T> &vec, F predicate) {
 		if (predicate(vec[i])) {
 			vec[i] = vec.back();
 			vec.pop_back();
+			// Note: can underflow, but it should be fine since it's incremented right after.
+			// TODO Use a while()?
 			--i;
 		}
 	}