Add Support for Geometry Node Cache (#92890)

Add support for geometry node simulation cache files.

This also adds support for dealing with dynamic arrays in Blender's
DNA, because `modifier.bakes` is a pointer to such an array.

Co-authored-by: Sybren A. Stüvel <sybren@blender.org>
Reviewed-on: https://projects.blender.org/blender/blender-asset-tracer/pulls/92890

blender_asset_tracer/blendfile/__init__.py

@@ -633,8 +633,8 @@ class BlendFileBlock:
         self.bfile.fileobj.seek(self.file_offset, os.SEEK_SET)
         return self.bfile.fileobj.read(self.size)
 
-    def as_string(self) -> str:
-        """Interpret the bytes of this datablock as null-terminated utf8 string."""
+    def as_bytes_string(self) -> bytes:
+        """Interpret the bytes of this datablock as null-terminated string of raw bytes."""
         the_bytes = self.raw_data()
         try:
             first_null = the_bytes.index(0)
@@ -642,6 +642,11 @@ class BlendFileBlock:
             pass
         else:
             the_bytes = the_bytes[:first_null]
+        return the_bytes
+
+    def as_string(self) -> str:
+        """Interpret the bytes of this datablock as null-terminated utf8 string."""
+        the_bytes = self.as_bytes_string()
         return the_bytes.decode()
 
     def get_recursive_iter(
@@ -820,6 +825,10 @@ class BlendFileBlock:
     def __setitem__(self, item: bytes, value) -> None:
         self.set(item, value)
 
+    def has_field(self, name: bytes) -> bool:
+        dna_struct = self.bfile.structs[self.sdna_index]
+        return dna_struct.has_field(name)
+
     def keys(self) -> typing.Iterator[bytes]:
         """Generator, yields all field names of this block."""
         return (f.name.name_only for f in self.dna_type.fields)

blender_asset_tracer/blendfile/iterators.py

@@ -20,6 +20,7 @@
 # (c) 2014, Blender Foundation - Campbell Barton
 # (c) 2018, Blender Foundation - Sybren A. Stüvel
 import typing
+import copy
 
 from blender_asset_tracer import cdefs
 from . import BlendFileBlock
@@ -70,3 +71,24 @@ def modifiers(object_block: BlendFileBlock) -> typing.Iterator[BlendFileBlock]:
     # 'ob->modifiers[...]'
     mods = object_block.get_pointer((b"modifiers", b"first"))
     yield from listbase(mods, next_path=(b"modifier", b"next"))
+
+
+def dynamic_array(block: BlendFileBlock) -> typing.Iterator[BlendFileBlock]:
+    """
+    Generator that yields each element of a dynamic array as a separate block.
+
+    Dynamic arrays are multiple contiguous elements accessed via a single
+    pointer. BAT interprets these as a single data block, making it hard to
+    access individual elements. This function divides the array into individual
+    blocks by creating modified copies of the original block.
+    """
+
+    element_size = block.dna_type.size
+
+    sub_block = copy.copy(block)
+    sub_block.size = element_size
+
+    for i in range(block.count):
+        # When sub_block's data is read, it'll be read from this offset in the blend file.
+        sub_block.file_offset = block.file_offset + i * element_size
+        yield sub_block

blender_asset_tracer/cdefs.py

@@ -52,6 +52,14 @@ eModifierType_MeshSequenceCache = 52
 eModifierType_Fluid = 56
 eModifierType_Nodes = 57
 
+# NodesModifierBakeFlag
+NODES_MODIFIER_BAKE_CUSTOM_PATH = 1 << 1
+
+# NodesModifierBakeTarget
+NODES_MODIFIER_BAKE_TARGET_INHERIT = 0
+NODES_MODIFIER_BAKE_TARGET_PACKED = 1
+NODES_MODIFIER_BAKE_TARGET_DISK = 2
+
 # DNA_particle_types.h
 PART_DRAW_OB = 7
 PART_DRAW_GR = 8

blender_asset_tracer/trace/modifier_walkers.py

@@ -27,6 +27,7 @@ import logging
 import typing
 
 from blender_asset_tracer import blendfile, bpathlib, cdefs
+from blender_asset_tracer.blendfile import iterators
 from . import result
 
 log = logging.getLogger(__name__)
@@ -337,7 +338,7 @@ def modifier_dynamic_paint(
 
     surfaces = canvas_settings.get_pointer((b"surfaces", b"first"))
 
-    for surf_idx, surface in enumerate(blendfile.iterators.listbase(surfaces)):
+    for surf_idx, surface in enumerate(iterators.listbase(surfaces)):
         surface_block_name = block_name + b".canvas_settings.surfaces[%d]" % (surf_idx)
         point_cache = surface.get_pointer(b"pointcache")
         if point_cache is None:
@@ -351,3 +352,62 @@ def modifier_dynamic_paint(
         yield from _walk_point_cache(
             ctx, surface_block_name, modifier.bfile, point_cache, cdefs.PTCACHE_EXT
         )
+
+
+@mod_handler(cdefs.eModifierType_Nodes)
+def modifier_nodes(
+    ctx: ModifierContext, modifier: blendfile.BlendFileBlock, block_name: bytes
+) -> typing.Iterator[result.BlockUsage]:
+    if not modifier.has_field(b"simulation_bake_directory"):
+        return
+
+    mod_directory_ptr, mod_directory_field = modifier.get(
+        b"simulation_bake_directory", return_field=True
+    )
+
+    bakes = modifier.get_pointer(b"bakes")
+    if not bakes:
+        return
+
+    mod_bake_target = modifier.get(b"bake_target")
+
+    for bake_idx, bake in enumerate(iterators.dynamic_array(bakes)):
+        # Check for packed data.
+        bake_target = bake.get(b"bake_target")
+        if bake_target == cdefs.NODES_MODIFIER_BAKE_TARGET_INHERIT:
+            bake_target = mod_bake_target
+        if bake_target == cdefs.NODES_MODIFIER_BAKE_TARGET_PACKED:
+            # This data is packed in the blend file, it's not a dependency to trace.
+            continue
+
+        flag = bake.get(b"flag")
+        use_custom_directory = bool(flag & cdefs.NODES_MODIFIER_BAKE_CUSTOM_PATH)
+
+        if use_custom_directory:
+            bake_directory_ptr, bake_directory_field = bake.get(
+                b"directory", return_field=True
+            )
+            directory_ptr = bake_directory_ptr
+            field = bake_directory_field
+            block = bake
+        else:
+            directory_ptr = mod_directory_ptr
+            field = mod_directory_field
+            block = modifier
+
+        if not directory_ptr:
+            continue
+        directory = bake.bfile.dereference_pointer(directory_ptr)
+        if not directory:
+            continue
+
+        bpath = bpathlib.BlendPath(directory.as_bytes_string())
+        bake_block_name = block_name + b".bakes[%d]" % bake_idx
+
+        yield result.BlockUsage(
+            block,
+            bpath,
+            block_name=bake_block_name,
+            path_full_field=field,
+            is_sequence=True,
+        )