What coordinate conventions (normalised range, origin, pixel centre, bit depth, premultiplication) do Nuke's STMap documentation and the openfx-misc STMap/IDistort/LensDistortion code use, and what do they leave unstated?
Nuke documents STMap UVs as the absolute source position normalised to 0-1, with (0,0) the bottom-left corner and (1,1) the top-right corner of the input, plus a premultiplied option for renderer output. It does not state the pixel-centre rule or bit depth. The open-source openfx-misc implementation makes the convention explicit: u,v map to the source rectangle with (0,0) at the lower-left corner of the first pixel, IDistort offsets sample at pixel centres (+0.5), UV input must be float, and there are unpremultiply and offset/scale options. A pixel-exact identity STMap therefore stores (x+0.5)/W and (y+0.5)/H (inference).
Nuke documents STMap UVs as the absolute source position normalised to 0-1, with (0,0) the bottom-left corner and (1,1) the top-right corner of the input, plus a premultiplied option for renderer output. It does not state the pixel-centre rule or bit depth. The open-source openfx-misc implementation makes the convention explicit: u,v map to the source rectangle with (0,0) at the lower-left corner of the first pixel, IDistort offsets sample at pixel centres (+0.5), UV input must be float, and there are unpremultiply and offset/scale options. A pixel-exact identity STMap therefore stores (x+0.5)/W and (y+0.5)/H (inference).
Curator qualifications: Docs and code read 2026-10-22; no map generated or applied. Nuke behaviour beyond its documentation not inspected (closed source).
Limitations: Docs and code read 2026-10-22; no map generated or applied.
Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.
Structured fields
{
"citations": [
{
"url": "https://learn.foundry.com/nuke/content/reference_guide/transform_nodes/stmap.html",
"note": "learn.foundry.com Nuke STMap reference (intro and controls); openfx-misc Distortion/Distortion.cpp at 850b3ff L105, L199, L1051-1065, L1083-1088, L2420-2421, L3431"
},
{
"url": "https://github.com/NatronGitHub/openfx-misc/blob/850b3fff65463c073bd64683e5d97a7dec2586c5/Distortion/Distortion.cpp",
"note": "learn.foundry.com Nuke STMap reference (intro and controls); openfx-misc Distortion/Distortion.cpp at 850b3ff L105, L199, L1051-1065, L1083-1088, L2420-2421, L3431"
}
]
}Evidence claims
- [sourced_fact] Nuke documents STMap UVs as the absolute source position normalised to 0-1, with (0,0) the bottom-left corner and (1,1) the top-right corner of the input, plus a premultiplied option for renderer output. It does not state the pixel-centre rule or bit depth. The open-source openfx-misc implementation makes the convention explicit: u,v map to the source rectangle with (0,0) at the lower-left corner of the first pixel, IDistort offsets sample at pixel centres (+0.5), UV input must be float, and there are unpremultiply and offset/scale options. A pixel-exact identity STMap therefore stores (x+0.5)/W and (y+0.5)/H (inference). · locator: learn.foundry.com Nuke STMap reference (intro and controls); openfx-misc Distortion/Distortion.cpp at 850b3ff L105, L199, L1051-1065, L1083-1088, L2420-2421, L3431 source
Rights
| component | license | hosting | redistribution | modification | training | Evidence and notes |
|---|---|---|---|---|---|---|
| documentation | unknown | permitted | permitted | unknown | unknown | Applies to this original summary only, not to the cited sources. |