houdini-render

name	houdini-render
description	Pipeline skill — viewport capture/flipbook plus ROP render settings and render execution through typed, runtime-aware tools. Exports report written_files, elapsed time, and separate error/warning diagnostics without hanging the host. Pair with houdini-camera-light to set up cameras and lights first.
license	MIT
compatibility	dcc-mcp-houdini 0.1+, Houdini 20.5+, dcc-mcp-core 0.19.45+
allowed-tools	Bash Read Write Edit
metadata	{"dcc-mcp":{"dcc":"houdini","layer":"domain","stage":"pipeline","version":"1.0.0","tags":["houdini","render","rop","karma","mantra","viewport","flipbook","capture","pipeline","aov","render_layer","takes"],"search-hint":"render rop karma mantra viewport capture flipbook screenshot render settings resolution output aov render layer takes stats","tools":"tools.yaml"}}

houdini-render

Typed render and visual-verification tools. Scene inspection and launch tools use affinity: main; background job polling and cancellation use affinity: any. Viewport tools are UI-aware: in a headless hython session they return a structured warnings payload with captured: false instead of failing, so an agent can detect and skip cleanly when rendering is unavailable.

Tool groups

• viewport: capture_viewport (single frame), flipbook (range with an optional positive increment and explicit camera). Both clamp resolution to 4096 and return written_files / skipped / warnings.
• render: get_render_settings (read-only), set_render_settings (reports unsupported fields per ROP type), render_rop (foreground or isolated hython background job), get_render_job (polls and reconciles status without blocking the UI), finalize_render_outputs (publishes externally validated staged EXRs without replacing finals), cancel_render_job (cancels only jobs owned by the current adapter process), configure_aovs (add/remove Solaris RenderVars or native Mantra auxiliary planes with renderer-correct processing), validate_karma_stage (read-only USD/Karma preflight), get_render_stats (read resolution/samples/renderer/output).
• render_layer: create_render_layer (Solaris RenderProduct or cloned Mantra ifd ROP with its own output and object masks), manage_takes (take lifecycle plus parameter-tuple overrides for render variants).

Tracer-bullet flow

Viewport/Render

1. houdini_camera_light__create_camera(name="rendercam")
2. set_render_settings(rop_path="/out/mantra1", camera="/obj/rendercam", resolution=[1280,720], output_path="/tmp/beauty.exr")
3. get_render_settings("/out/mantra1") → verify
4. capture_viewport(output_path="/tmp/preview.jpg") for a quick look (UI only)
5. flipbook(output_path="/tmp/preview.$F4.jpg", frame_range=[1,24,4], camera_path="/obj/rendercam") for a sparse camera preview (UI only)
6. render_rop("/out/mantra1", frame_range=[1,1]) → background job_id in interactive or headless Houdini

For crash-safe final publication, opt in with artifact_transaction={"mode":"staged_no_clobber"} and an explicit integral frame range. Poll the worker to completed, validate each returned staging EXR externally, then pass the identity-bound receipts to finalize_render_outputs(job_id, validator_receipts). The worker discovers and temporarily overrides the exact EXR output parameter only in its loaded HIP copy. Final paths are created only by the no-clobber finalize step.

Render Layers & AOVs

1. For Solaris, create_render_layer(name="beauty", parent_path="/stage", purpose="beauty", aovs=["diffuse","specular","normal","depth"]).
2. For Mantra, clone a real pass with an output distinct from its source: create_render_layer(name="solar_fx", parent_path="/out", source_rop_path="/out/mantra1", output_path="/tmp/solar_fx.$F4.exr", candidate_objects="/obj/sun_fx", exclude_objects="/obj/labels", aovs=["emission","depth"]).
3. configure_aovs(rop_path="/out/solar_fx", aovs=["normal","depth","normal"], action="add") adds only missing Mantra planes; action="remove" removes matching preset/source/channel planes and compacts the multiparm.
4. validate_karma_stage(lop_path="/stage/OUT", renderer="karma_xpu") → inspect instance and RenderVar diagnostics.
5. get_render_stats(rop_path="/out/solar_fx") → verify resolution/samples/output.

Takes

1. manage_takes(action="create", take_name="lighting_variant_a")
2. manage_takes(action="add_override", take_name="lighting_variant_a", node_path="/out/solar_fx", parm_name="vm_picture", value="/tmp/lighting_variant_a.$F4.exr") → add and set the take-local parameter while restoring the previously current take.
3. manage_takes(action="remove_override", take_name="lighting_variant_a", node_path="/out/solar_fx", parm_name="vm_picture") → remove it with the same restoration guarantee.
4. manage_takes(action="switch", take_name="lighting_variant_a")
5. manage_takes(action="list") → review all takes

Interactive Houdini defaults to an isolated process; poll get_render_job(job_id) and use cancel_render_job(job_id) to stop a job started by the same adapter process. Pass background=false only when foreground execution is intentional. Both interactive and headless Houdini default to isolated background execution. The default poll response is bounded: it reports completed, total, fractional progress, elapsed_secs, eta_secs, written_file_count, and up to ten recent_written_files. output_verification.state distinguishes verified, partial, failed, not_observed, and unavailable output evidence. verified requires every expected output to be newly written, readable, non-empty, and produced without an execution/cook failure. Pass an explicit frame range when exact completeness matters; render and cache jobs with only part of that requested range written fail with bounded output counts. Transaction polling additionally returns a bounded transaction state and aggregate; use include_details=true for per-frame staging, validator, commit, and post-commit verification evidence. Pass include_details=true only when the full expected-output snapshot, complete written-file and warning lists, error, and traceback are needed. The same job lifecycle also observes cache_simulation and execute_rop_chain jobs. ROP-chain completion is governed by execution/cook errors; a chain without a discoverable output pattern can complete with output_verification.state set to unavailable. Render and cache jobs still require a new or updated output. Interactive background launch requires a saved HIP with no unsaved changes and never auto-saves the GUI scene. Headless background launch requires an existing HIP and captures its current state in a job-owned temporary HIP snapshot without saving or renaming the source scene. The main thread only validates the ROP and launches the isolated process; Mantra/Karma work never occupies Houdini's event loop. Output-path and resolution parameter writes are defensive (candidate names) so Mantra, Karma, and ROP geometry/USD drivers are all tolerated.