dtourolleandClaude Opus 5
4a2fcb6d22
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>
23 lines
1000 B
YAML
23 lines
1000 B
YAML
id: film_sim
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order: 25
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attributes: [tone, colour]
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rust: FilmSim
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why_rust: |
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It carries a stock's measured tables — an exposure matrix, three
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characteristic curves and a density lookup — which are not parameters and
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which no `uniforms:` expression could produce. Its neutral is "no stock
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loaded" rather than a set of values, and it is the one node that declares
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`Operation::renders`, so the composer omits the camera profile's base curve
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and the conversion out of camera space on its behalf.
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placement: |
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After white balance and exposure, and before everything else.
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Those two are what the camera did — interpreting the sensor, and correcting
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the amount of light that reached it — and they are only meaningful on
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scene-linear values, which is what a film has to be handed. Everything below
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is a decision about the picture, and a decision about the picture belongs
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after the film has rendered it, exactly as it does when you scan a frame and
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then work on the scan.
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