feat: Add new Geometry Nodes groups for image relief and shadeless shader

- Implemented the "O Image Relief Plane" Geometry Nodes group to create a fixed-base image relief using depth images and various parameters.
- Created the "O Shadeless" shader node group to display color without scene lighting while preserving shadows and reflections.
- Introduced a preview feature for node groups, allowing for interactive visualization of node arrangements in an HTML format.
- Added a template HTML file for rendering node previews with customizable views and controls.

tools/nodes/common/nodes.py

@@ -0,0 +1,106 @@
+"""Build interfaces and basic nodes shared by asset definitions."""
+from types import SimpleNamespace
+
+
+def prepare_node_group(node_group):
+    """Hide unused outputs and discard disconnected interface nodes."""
+    for node in list(node_group.nodes):
+        for socket in node.outputs:
+            socket.hide = not socket.is_linked
+        if node.bl_idname == "NodeGroupInput" and not any(socket.is_linked for socket in node.outputs):
+            node_group.nodes.remove(node)
+
+
+def interface_socket(group, name, in_out, socket_type, parent=None):
+    socket = group.interface.new_socket(
+        name=name,
+        in_out=in_out,
+        socket_type=socket_type,
+        parent=parent,
+    )
+    if in_out == "INPUT" and hasattr(socket, "structure_type"):
+        socket.structure_type = "SINGLE"
+    return socket
+
+
+def group_input(nodes, visible_names):
+    node = nodes.new("NodeGroupInput")
+    visible = set(visible_names)
+    for output in node.outputs:
+        output.hide = output.name not in visible
+    return node
+
+
+def float_input(
+    group,
+    name,
+    default,
+    minimum=0.0,
+    maximum=None,
+    subtype=None,
+    parent=None,
+):
+    socket = interface_socket(group, name, "INPUT", "NodeSocketFloat", parent)
+    socket.default_value = default
+    socket.min_value = minimum
+    if maximum is not None:
+        socket.max_value = maximum
+    if subtype is not None:
+        socket.subtype = subtype
+    return socket
+
+
+def bool_input(group, name, default=False, parent=None):
+    socket = interface_socket(group, name, "INPUT", "NodeSocketBool", parent)
+    socket.default_value = default
+    return socket
+
+
+def vector_input(group, name, default, subtype=None, parent=None):
+    socket = interface_socket(group, name, "INPUT", "NodeSocketVector", parent)
+    socket.default_value = default
+    if subtype is not None:
+        socket.subtype = subtype
+    return socket
+
+
+def math_node(nodes, operation):
+    node = nodes.new("ShaderNodeMath")
+    node.operation = operation
+    return node
+
+
+def menu_switch(group, control, names, kind):
+    selector = next((node for node in group.nodes if node.bl_idname == "GeometryNodeMenuSwitch" and node.inputs["Menu"].is_linked and node.inputs["Menu"].links[0].from_socket.name == control), None)
+    if selector is None:
+        selector = group.nodes.new("GeometryNodeMenuSwitch")
+        selector.data_type = "BOOLEAN"
+        for item, name in zip(selector.enum_items, names):
+            item.name = name
+        selector.inputs[names[0]].default_value = False
+        selector.inputs[names[1]].default_value = True
+        local = group_input(group.nodes, {control})
+        group.links.new(local.outputs[control], selector.inputs["Menu"])
+    node = group.nodes.new("GeometryNodeSwitch")
+    node.input_type = kind
+    group.links.new(selector.outputs[0], node.inputs["Switch"])
+    return SimpleNamespace(inputs={names[0]: node.inputs["False"], names[1]: node.inputs["True"]}, outputs=node.outputs)
+
+
+def read_float_attribute(group, name):
+    node = group.nodes.new("GeometryNodeInputNamedAttribute")
+    node.data_type = "FLOAT"
+    node.inputs["Name"].default_value = name
+    return node.outputs["Attribute"]
+
+
+def store_float_attribute(group, geometry, name, value, domain="POINT"):
+    node = group.nodes.new("GeometryNodeStoreNamedAttribute")
+    node.domain, node.data_type = domain, "FLOAT"
+    node.inputs["Name"].default_value = name
+    group.links.new(geometry, node.inputs["Geometry"])
+    if isinstance(value, (int, float)):
+        node.inputs["Value"].default_value = value
+    else:
+        group.links.new(value, node.inputs["Value"])
+    return node.outputs["Geometry"]