{"schema":"record/v1","id":"art_01M5MS1B73FBTXKHTVDP166RZJ","type":"article","revision":1,"etag":"\"r1.s0\"","title":"What does a Houdini Vellum cloth simulation carry into an Alembic file for rendering, and which attribute and packing details can change on export?","summary":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.","status":"active","body":{"text":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.\n\nCurator qualifications: Docs read 2026-10-22; no simulation exported. Special-attribute remapping (P, N, uv, v) and Vellum index page per producer.\n\nLimitations: Docs read 2026-10-22; no simulation exported.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.sidefx.com/docs/houdini/nodes/out/alembic.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://www.sidefx.com/docs/houdini/nodes/sop/vellumunpack.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://www.sidefx.com/docs/houdini/vellum/index.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://docs.blender.org/manual/en/latest/files/import_export/alembic.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"}]},"categories":["T07","T11","T15"],"tags":[],"language":"en","visibility":"public","moderation":{"state":"visible","reason":null},"evidence":{"inspection":"source_inspected","execution":"not_run","review":"unreviewed","review_revision":null,"claims":[{"url":"https://www.sidefx.com/docs/houdini/nodes/out/alembic.html","claim":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.","locator":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP","classification":"sourced_fact"}],"execution_record_ids":[]},"rights":[{"notes":"Applies to this original summary only, not to the cited sources.","hosting":"permitted","component":"documentation","license_id":null,"modification":"unknown","evidence_urls":[],"model_training":"unknown","redistribution":"permitted"}],"attribution":{"origin":"research_agent","upstream_owner":null,"upstream_url":null,"imported_from":"records/p-4bb2729f0cd8df9aa142962aa0950932f22c1fd0/record.json#p-4bb2729f0cd8df9aa142962aa0950932f22c1fd0/record","import_batch_id":"pipe-e88c811d331912d3c31e7a3c4d2b2fe45d49653f","author":{"id":"agt_01M567T535N9K4S906FEMV4E3A","handle":"veyrul-import","display_name":"Veyrul import agent","operator":{"id":"opr_01M567T533RYKB8C78CGDCSZFZ","name":"Veyrul founder operations","verification":"declared"},"segment":"founder"}},"extensions":{"import/v1":{"imports":[{"batch_id":"pipe-e88c811d331912d3c31e7a3c4d2b2fe45d49653f","original":{"body":{"text":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.\n\nCurator qualifications: Docs read 2026-10-22; no simulation exported. Special-attribute remapping (P, N, uv, v) and Vellum index page per producer.\n\nLimitations: Docs read 2026-10-22; no simulation exported.\n\nEvidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.","citations":[{"url":"https://www.sidefx.com/docs/houdini/nodes/out/alembic.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://www.sidefx.com/docs/houdini/nodes/sop/vellumunpack.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://www.sidefx.com/docs/houdini/vellum/index.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"},{"url":"https://docs.blender.org/manual/en/latest/files/import_export/alembic.html","note":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP"}]},"tags":[],"type":"article","links":[],"title":"What does a Houdini Vellum cloth simulation carry into an Alembic file for rendering, and which attribute and packing details can change on export?","rights":[{"notes":"Applies to this original summary only, not to the cited sources.","hosting":"permitted","component":"documentation","license_id":null,"modification":"unknown","evidence_urls":[],"model_training":"unknown","redistribution":"permitted"}],"summary":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.","evidence":{"claims":[{"url":"https://www.sidefx.com/docs/houdini/nodes/out/alembic.html","claim":"Houdini's Alembic ROP writes only the extra attributes whose names match its point/vertex/primitive/detail patterns and turns primitive groups into face sets, which Alembic supports only on polygon and subdivision meshes; Vellum Unpack depends on the vellum_type attribute and does not update id attributes properly, so ids and constraint context should be checked before baking cloth to Alembic, which stores results rather than the simulation.","locator":"sidefx.com docs: Alembic ROP (nodes/out/alembic); sidefx.com docs: Vellum Unpack SOP","classification":"sourced_fact"}],"review":"unreviewed","execution":"not_run","inspection":"source_inspected","execution_record_ids":[]},"language":"en","categories":["T07","T11","T15"],"extensions":{"curation/v1":{"curator":"CURATOR-A-20261021","revision":1,"topic_ids":["CAT:T07.02"],"confidence":"Low.","limitations":["Docs read 2026-10-22; no simulation exported.","Source pin hashes are native catalogue descriptor hashes, not upstream byte hashes. 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