06 render
Render is the native fractal video factory. It takes a Save composition result, writes a verified PNG sequence (and per-frame .params JSON), then assembles video with ffmpeg.
This tab is not Psychedelia / Generator Lab / Shader Lab. Those publish with Render final output inside Videos. Auto jobs still appear here in a read-only Render activity list.
Render setup with the saved composition and a 640 × 360 test size.
Left column heading Render setup. The primary button at the top uses a dynamic label:
| Queue state | Button label |
|---|---|
| Empty | Render selected |
| One or more items | Render queued (N) |
Tooltip: if the queue is non-empty, render every queued composition front-to-back; otherwise render the selected composition only. The same button is repeated at the bottom of the column.
Dropdown Renderer. Status text under it reports availability (HLSL GPU vs CPU). CPU uses the CPU workers budget from Resources.
Dropdown Composition lists saved compositions. Empty state: (no saved compositions - build one on the Compose tab).
X beside the dropdown deletes the selected saved composition (tooltip Delete selected composition). Videos already rendered are not deleted.
Output directory text box (mono path). browse... replaces the path. open opens the folder in Explorer.
Default is the app output folder (or FRACTALFLOW_OUTPUT_DIR).
| Control | Role |
|---|---|
| Width override (blank = use composition) | Optional width. Blank keeps the composition width. |
| Height override (blank = use composition) | Optional height. |
Blank overrides are the right choice when Compose already has the framing you want.
landscape: 720p (1280×720), 1080p, 1440p, 4K, clear (clear override — render at the composition’s stored resolution).
portrait: 720, 1080, 1440, 4K, swap (flip width/height). Portrait tooltip: 9:16 Shorts / Reels / TikTok.
See the Render setup with the saved composition and a 640 × 360 test size screenshot.
Heading Render queue. Status text on the right reports how many items are waiting.
| Control | Role |
|---|---|
| List | Pending compositions, front to back. |
| + Add to queue | Append the currently selected composition. Duplicates are skipped. |
| up / down | Reorder the highlighted item. |
| X | Remove the highlighted item. |
| clear | Empty the queue. |
Empty queue + Render selected = one-off render of the dropdown composition. Non-empty queue + Render queued (N) = overnight batch.
This queue is only for manual Render-tab jobs. Auto-created work is not added here and cannot be reordered/removed by these buttons.
Heading Render activity, badge read-only.
Tooltip: live activity from Classic Auto, procedural creation, and Clip Studio preview/export. Control Auto jobs from Auto and Clip Studio work from Videos. This view never owns or duplicates them.
Each row shows name, status, progress bar, progress summary, resource summary (which GPUs/CPU), and detail/error.
- Render selected / Render queued (N) starts work.
- Cancel stops the current Render-tab job.
The right pane is progress plus a scrolling log.
- Per-frame PNGs (
frame_*.png) and per-frame.paramsJSON. - ffmpeg assembles the video according to Resources → Final output (H.264 MP4 quality/encoder, or lossless MKV, or PNG-only). NVENC is used when a mapped NVIDIA GPU is enabled; otherwise ffmpeg falls back to CPU encoding.
- Valid cached PNG frames are reused on retry; missing frames are rendered. Cache reuse requires a matching render identity, including FPS. Changing frame rate invalidates an old implicit-time frame sequence.
- Rendering does not drop or resample frames. Frame dropping belongs to Clip Studio export FPS after the source frames exist.
- If cleanup is enabled on Resources, frame PNGs and intermediate directories are removed only after MP4 assembly succeeds. Classic Render-tab resume behavior is unchanged: you can retry a partial job.
Keep PNG frame sequence on Resources is the global policy for whether those PNGs stay on disk (especially important for Clip Studio, which prefers a complete PNG sequence when present).
Output lands in output\<name>_id<NNNN>\.
- Save composition after your final edit. Render uses the saved composition, not an unsaved Compose draft.
- Check the name in Render's Composition picker. With queued items present, Render queued (N) renders those items rather than only the picker selection. Remove unwanted queue entries before a one-off render.
- Keep the same renderer used for the approved Compose preview. Changing backend invalidates that preview; CPU/GPU lighting and some formula implementations can differ.
- Clear both size overrides to use the saved aspect ratio, or enter dimensions with the same ratio. A 16:9 composition rendered at 9:16 is a new framing decision.
- Compare the same timeline time. A still thumbnail or the first frame does not represent every camera/seed state in the clip. Preview is sampled at approximately 8 FPS; export uses the composition FPS.
- If a discrepancy remains, keep a short diagnostic PNG sequence and compare a frame before MP4 compression. Report the composition name, renderer, frame/time, dimensions, FPS, and today's log.
Saving over a composition refreshes pending queue references. An already prepared/running job keeps its resolved input; cancel it and start a new job if you want later edits included. Missing/corrupt source snapshots or LUT assets stop loading rather than silently dropping part of the image.
MP4 is lossy. Small color or edge differences after H.264 encoding are different from missing layers, different cameras, or an unrelated animation. Use lossless MKV or retained PNGs for an archival comparison. See Troubleshooting.
Completed render: 480 frames from the saved 16-second composition.
- After success, open Videos. The clip should appear in Video library. Use Clip Studio to trim/retime/effect.
- Auto Builder Classic jobs use this same native HLSL multi-GPU route. Watch them here; cancel/retry/clear them on Auto.
- Procedural Render final output jobs also show in Render activity as read-only.
Continue: Videos or Resources to set format/quality before a long queue.