Path-trace a still

manfred render path-traces a recipe through a camera on the engine’s GPU tracer (hardware ray queries, adaptive sampling, a port of Intel Open Image Denoise). It stages the same parts, materials, sky, sun and lights the live renderer draws, so a render and a manfred shot of one recipe show one scene.

A final and a draft

manfred render showcase/hero.toml --camera hero --out hero.png
manfred render showcase/hero.toml --camera hero --draft --out hero-draft.png

A final traces each pixel until its noise is under 0.01, at least 16 samples and at most 64, then denoises. --draft is a quick look at the same size: at most 12 samples, threshold 0.05, 6 first. On a Radeon RX 9060 XT a 4K final of the workshop’s hero camera takes 7.5 s and a 4K draft 2.9 s.

stdout gets the file written; stderr gets a summary:

$ manfred render desk.toml --camera main --draft --size 800x500 --out draft.png
manfred render: 800x500, 7.3 samples a pixel on average, 12 at most of 12, threshold 0.05, seed 0: 19 submissions, the longest 5.87 ms, 31 ms on the GPU
draft.png

Samples and noise

Flag	Default	Meaning
--spp N	the recipe’s [trace] spp, else 64	the most samples any pixel takes
--threshold T	the recipe’s [trace] threshold, else 0.01	a pixel stops once its noise is under this; 0 runs every pixel to --spp
--min-samples N	the recipe’s [trace] min_samples, else 16	samples every pixel takes before it may stop
--seed S	the recipe’s seed	the tracer’s seed
--denoise off|on	on for .png and a master	off writes the raw trace

A recipe can set its own defaults:

[trace]
spp = 128
threshold = 0.05
filter_glossy = 0.25

filter_glossy and clamp_indirect tame fireflies under a small sun; the recipe has the ranges.

Formats and sizes

• --out picks the format by its extension: .png (8-bit, dithered, through the recipe’s [look]), .exr or .hdr (linear, unfinished).
• --master <file.png> also writes a 16-bit PNG of the same finished picture.
• --size WxH sets the frame (1586x992 by default); --equirect renders the full sphere around the camera (2048x1024 by default) and --ortho an orthographic view of the camera’s ortho_height.

A crop of a bigger frame

--crop x,y,w,h traces only that rectangle of the --size frame, with each pixel keeping its place in the full frame’s random stream, ray and lens:

$ manfred render desk.toml --camera main --size 800x500 --crop 200,100,200,150 --out crop.png
manfred render: 200x150 at 200,100 of 800x500, 41.0 samples a pixel on average, 64 at most of 64, threshold 0.01, seed 0: 23 submissions, the longest 5.83 ms, 33 ms on the GPU
crop.png

With --denoise off, or as .exr or .hdr, a crop has the full frame’s pixels exactly. Denoised, it is within a level or two: the denoiser sets its exposure from the picture it is given. A .png crop is refused when the recipe’s finish cannot be worked out on a margin (overlay text, grain, outlines).

Progress for a program

--progress json writes one JSON object a line on stderr, with a stage of stage, trace, write and done:

{"elapsed_s":0.0,"stage":"stage"}
{"cap":64,"elapsed_s":0.1,"eta_s":null,"fraction":0.0,"gpu_s":0.0,"stage":"trace","threshold":0.01}
{"elapsed_s":0.5,"stage":"write"}
{"elapsed_s":0.5,"gpu_s":0.2,"mean_samples":37.9,"most_samples":64,"out":"final.png","stage":"done"}

File formats lists every field.

The GPU queue

When pgpu is on the PATH, manfred render queues itself as a pgpu job and waits its turn; without it, it renders at once, paced the same way, so it never holds the desktop’s GPU for long. A GPU below the tracer’s floor is refused in one line, exit 1.

Same input, same picture

The tracer reads no clock and no system randomness: the same recipe, flags and seed give the same pixels on the same GPU and driver.