b502a8ef901f5f4410821815ce18d5f339f76131
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Commits
| Author | SHA1 | Message | Date | |
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  dtourolleandClaude Opus 5
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ce6458547a |
Develop longer, from the measurements rather than from a contrast slider
Pushing was not a thing to simulate. It was measured data being thrown away: Double-X and 2302 each ship five characteristic curves, one per development time, and this shipped the 6.5-minute column and discarded four. All five now ship and interpolate. The axis is real. Double-X runs 4 to 12 minutes, and across it the average gradient goes 0.472 to 1.034 while Dmax goes 1.19 to 2.56. The control is in stops, because that is what a photographer means, and one stop is a factor of about 1.41 in time. That mapping is checked rather than assumed: against Double-X's own axis it lands within 2% of the 9-minute column for +1, and near 12 minutes for +2, which are the times the datasheet gives for exactly that. There is a test. **Pushing must not recover shadow detail, and this does not.** Across the whole measured range the speed point moves about a third of a stop while the gradient doubles; three stops under mid-grey, density goes from 0.008 to 0.035, which is still nothing. Developing longer multiplies what was already recorded and cannot record what never hit the film. A push built as added exposure or global contrast brightens those shadows instead and looks convincing until someone who shoots film sees it, so that property has a test of its own. Interpolated in *log* time, because development is multiplicative: 4 to 5 minutes is the same amount of push as 9 to 12, and interpolating linearly would bunch the control at one end. Clamped at both ends, because past the published range there is no data and extrapolating a contrast curve invents an emulsion nobody tested. A stock measured at one process ignores the control entirely rather than inventing a curve for it -- Portra 800's pushes are separate *measured* profiles, which is the honest way to offer those. Costs nothing per pixel and changes no shader. The curves are a per-stock table, so the interpolation happens on the CPU at bake time, where choosing a stock and moving its sliders already rebakes. The Vulkan shader is untouched. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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dtourolleandClaude Opus 5
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3b5952769b |
Emit floats an f32 can hold, and drop the format! that formats nothing
CI runs cargo fmt --check and clippy -D warnings, and this branch had never been through either. Both would have failed it. The bulk was the generated colour tables: eight significant figures where an f32 carries about 7.2, so the eighth is noise that rounds away at compile time and clippy's excessive_precision says so 109 times over. Fixed in the generator rather than only in the file, so it stays fixed -- and the file is trimmed in place rather than re-derived, because regenerating it needs a colour-science stack that has nothing to do with the defect. The format! in the composer is mine too, from extracting the rendering tail: the braces in it were escaped because the text used to live inside a larger template, and once extracted the escapes are noise and the call formats nothing. Also here, and clearly not mine: an unused import and a shadowed binding in dr-gpu, and an unused import in a test. They are pre-existing -- clippy has been failing on master before this branch existed, on lints like is_multiple_of that arrived with a toolchain rather than with anyone's code. Fixed because CI cannot go green around them, and called out because a merge commit is a bad place to quietly edit someone else's crate. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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dtourolleandClaude Opus 5
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4a2fcb6d22 |
Render a film stock on the GPU, and let it take over the rendering
The stock model landed in dr-film with no way to see it. This is the pipeline node, the two texture bindings it reads, and the end-to-end test that proves the shader agrees with the model. The design point is that a film simulation is not an adjustment. Every other node changes a picture; this one makes it. A stock's characteristic curve does the camera profile's base curve's job -- from measurements rather than from a curve somebody drew -- so running both renders the scene twice: the camera's rendering, and then a film's rendering of that. It looks like neither, and it reads as a colour-management bug with no colour-management bug to find. So `Operation::renders` is new. A node declaring it takes camera RGB and hands back linear sRGB, and the composer emits neither the base curve nor the conversion out of camera space. Both halves move together, and the composer keeps them as one string precisely so that getting half of it right is impossible. The tables are not parameters, for the reason vignetting's coefficients are not: they are measurements. dr-pipeline declares the layout as a plain struct and keeps its no-dependency property; the two crates share no types on purpose. `EditGraph::set_film_tables` offers them to every node rather than to the one that wants them, because knowing which concrete type is which is what the graph is organised not to know. Bindings 4 and 5 follow the masks precedent: declared unconditionally so one bind group layout serves every generated shader, bound to 1x1 placeholders when no stock is loaded. Both are interpolated by hand with textureLoad -- this pipeline binds no sampler, and adding one for two lookups would cost a binding in every shader. Uploads are keyed on content so an unchanged stock does not push half a megabyte across the bus per frame. The end-to-end test earned its place immediately: it found the density lookup being filled z-fastest while a 3D texture upload wants x-fastest, so the red and blue axes were transposed. Green matched exactly, which is what that bug looks like -- a plausible photograph of the wrong colour, and one that every unit test on either side of the seam passes. dr-film now pins the layout in a test that needs no device, and states it where the field is declared. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> |
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dtourolleandClaude Opus 5
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b6a95e1965 |
Simulate a film stock from its measurements, not from someone's grade
FR-DEV-3f asks for look emulation and proposes HaldCLUT import to inherit
the free film-simulation ecosystem. This takes the other road for the
stocks where the measurements exist: run the physics.
A stock here is its manufacturer's own datasheet -- spectral sensitivity,
characteristic curves, dye densities. Light exposes three emulsion layers,
the layers develop to densities, the densities are dyes that absorb, and
what is left is what reaches the eye. A colour negative comes out orange
and upside down because that is what a colour negative is; it becomes a
photograph when a paper profile prints it, with the enlarger's filtration
solved rather than dialled.
What that buys over a LUT is that the parameters stay physical. Opening up
a stop moves the picture along the film's real characteristic curve,
shoulder and all, instead of scaling a number baked at one exposure. The
data cost runs the other way too: a stock is 17 kB of published
measurements where one HaldCLUT is 800 kB of one person's grade.
It looks like it needs a spectral integration per pixel. It does not, and
that is the whole design:
- Exposure is a 3x3 matrix. The reconstructed scene spectrum is linear
in the sRGB triple, so the integral collapses into nine numbers,
exactly -- no approximation.
- The characteristic curve is three 1D functions, sampled exactly.
- Everything after that -- dye absorption, the print through the
negative, the paper, the viewing illuminant, the adaptation -- takes
exactly three numbers in, so it bakes into one 32^3 lookup.
Per pixel: a matrix multiply, three curve taps, one fetch. Splitting the
curve out of the 3D lookup rather than baking one LUT over exposure is
measured, not assumed: the curve carries the sharp shape and the dye
mixing is smooth, so folding them together would need three times the
resolution for the same error. At 32^3 the worst error is 0.003 in linear
sRGB, under one 8-bit code value, and a test says so.
No wgpu dependency, deliberately, and the same isolation argument dr-lens
makes: the model is plain f32 with a documented layout, so every property
worth asserting is asserted on the CPU. Binding it to a texture is dr-gpu's
job and is not done here yet.
The expected values in tests/ came from a Python prototype running against
a different colour-science stack. Agreement to three decimals is evidence
about the model rather than about one implementation of it -- a transposed
matrix or a mispasted observer row would pass every unit test and fail
that one.
Profiles are converted from spektrafilm by Andrea Volpato, CC BY-SA 4.0.
The converter is in the tree and runnable, so what was changed from
upstream is auditable rather than taken on trust; profiles/CHANGELOG.txt
records it, including the one deliberate deviation -- Mallett & Yuksel's
1 kB basis instead of Hanatos's 4 MB table, which costs accuracy at the
gamut edge and saves four megabytes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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