NVIDIA-Omniverse Results + post-processing
No ovrtx; pure PIL / OpenCV / (optional) ffmpeg. Run in a thread-pool executor so it never blocks the control plane or the render thread.
Browse — list_results(dir)
Enumerate the rendered stills ({label}.png and {label}/####.png sequences) and videos
({label}.mp4) in a folder for the Results UI. Serve files via GET /api/frame?path= /
GET /api/video?path= (validate the suffix + that the file exists).
Overlay labels — overlay_all(dir) -> count
Burn a label plate (e.g. NVIDIA-green "{set}: {variant}") onto each render and write the
labeled copy into a _labeled/ subfolder. Originals are never modified (the Results UI
keeps showing the clean renders; labels are a derived artifact). Handle BOTH layouts: a
folder of frames AND top-level single stills {label}.png — a folder-only implementation
silently overlays nothing for the common single-still / Cartesian batch.
Label parsing (recover {set}: {variant} from the filename): set names contain _ (e.g.
Wheel_Colors), so do NOT split on _. Accumulate _-segments until a - boundary between
{set}-{variant} pairs (the inverse of the batch naming convention). Cache-bust the served
URL (&t=) so an overlaid frame reloads in the browser.
Video — frames_to_video(frame_dir, out_path, fps)
Assemble a numbered frame sequence into an MP4: H.264 (libx264) + pix_fmt yuv420p via
imageio-ffmpeg — NEVER OpenCV cv2.VideoWriter with mp4v. MPEG-4 Part 2 writes a
valid-looking file that /api/video serves fine and Chrome's <video> silently cannot decode →
the Results player shows NOTHING. yuv420p needs even dimensions, so pad
minimally (macro_block_size=2) rather than letting ffmpeg snap to 16. mp4v survives ONLY as an
explicit last-resort fallback for when no ffmpeg binary is available at all (imageio-ffmpeg not
importable). This is PUBLIC and reused by the batch animation_range path AND the timeline render —
a codec regression here breaks both. convert_all_to_videos(dir, fps) walks a results folder and
encodes each sequence. compress_video (ffmpeg 2-pass) is optional — return gracefully (no-op) if
ffmpeg is absent rather than failing.
Cut sheet — make_cut_sheet(dir) -> path
Compose all variant stills in a folder into one labeled contact-sheet image (a grid with each
cell labeled by its {set}: {variant}). One image to compare the whole sweep at a glance.
API
POST /api/post/overlay {out_dir} -> {count} · POST /api/post/cutsheet {out_dir} -> {path}
· POST /api/post/video {out_dir,fps} -> {count} · POST /api/post/compress {video_path} -> {path} — all run_in_executor. The Results tab drives these and previews via the frame/video
routes.