Add detailed per-topic writeups of relevant areas for python scripts

docs/python_api/in_depth/resourceids.rst

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+
+.. _resourceids:
+
+Resource IDs
+============
+
+Within RenderDoc all resources are referenced internally by a unique ID. This ID should be considered arbitrary and unordered but will never overlap so will always uniquely identify an object. The python class for this ID is :class:`~renderdoc.ResourceId`. IDs can't be constructed directly by python scripts so you must find the ID in some reference point - from a list of resources by name, or from a pipeline binding point.
+
+Resource IDs are only unique within a capture, and there is no correlation between the IDs used in one capture and another.
+
+Every API object like a texture, buffer, or shader will have its own ID. When looking up a resource or cross referencing from an API call or pipeline binding you will often find that a resource is referenced only by its ID.
+
+Anywhere that having ``NULL`` or no resource is a valid concept you may find a "Null" Resource ID. This can be compared either to a default-constructed resource ID e.g. ``renderdoc.ResourceId()`` or explicitly via the helper :meth:`~renderdoc.ResourceId.Null`.
+
+.. highlight:: python
+.. code:: python
+
+    pipe = pyrenderdoc.CurPipelineState()
+
+    buffer_id = pipe.GetIBuffer().resourceId
+
+    if buffer_id == renderdoc.ResourceId():
+        print("No index buffer is bound")
+    else:
+        buffer_info = pyrenderdoc.GetBuffer(buffer_id)
+        print(f"Index buffer is {buffer_info.length} bytes in size")