# How do STMap/UV-map conventions relate to OpenCV remap maps and to the 3DE and OpenCV lens-model coordinates implemented in openfx-misc?

- id: art_01M5NNWFYW6ENC6R67BZKEQRFS
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T11, T12 · tags: none
- updated: 2026-10-24T00:45:01.270Z
- url: https://veyrul.com/articles/art_01M5NNWFYW6ENC6R67BZKEQRFS

OpenCV remap (40738fb1) documents absolute source-coordinate maps (float or fixed-point, optional relative mode) without stating an origin or pixel-centre convention in the text read; openfx-misc LensDistortion (850b3fff) passes pixel-centre coordinates (x+0.5, y+0.5) to models whose origin is the bottom-left corner of the bottom-left pixel.

OpenCV remap (40738fb1) documents absolute source-coordinate maps (float or fixed-point, optional relative mode) without stating an origin or pixel-centre convention in the text read; openfx-misc LensDistortion (850b3fff) passes pixel-centre coordinates (x+0.5, y+0.5) to models whose origin is the bottom-left corner of the bottom-left pixel.

Curator qualifications: The STMap-to-OpenCV conversion (map_x = u*W - 0.5, map_y = (1-v)*H - 0.5) is conditional synthesis: it depends on an OpenCV centre/origin convention not stated in the remap text, and per AUDIT3 row 4 may be published only tied to the L10 remap fixture; C2-B07-E-03 is not evidence for it. OpenCV intrinsics/pixel-unit comment (E5) and 3DE4 parameters (E6) not re-read. Static reading only; no resize, remap or distortion run. Index arithmetic below is curator hand calculation.

Limitations: Static reading only; no resize, remap or distortion run. Index arithmetic below is curator hand calculation.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://github.com/NatronGitHub/openfx-misc/blob/850b3fff65463c073bd64683e5d97a7dec2586c5/Distortion/Distortion.cpp",
      "note": "imgproc.hpp lines 2168-2206 at 40738fb1; Distortion.cpp lines 1079-1090 at 850b3fff; DistortionModel.h lines 179-190"
    },
    {
      "url": "https://github.com/NatronGitHub/openfx-misc/blob/850b3fff65463c073bd64683e5d97a7dec2586c5/Distortion/DistortionModel.h",
      "note": "imgproc.hpp lines 2168-2206 at 40738fb1; Distortion.cpp lines 1079-1090 at 850b3fff; DistortionModel.h lines 179-190"
    },
    {
      "url": "https://github.com/opencv/opencv/blob/40738fb16ceddb5fb3fea747585f7ce6abb0605b/modules/imgproc/include/opencv2/imgproc.hpp",
      "note": "imgproc.hpp lines 2168-2206 at 40738fb1; Distortion.cpp lines 1079-1090 at 850b3fff; DistortionModel.h lines 179-190"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] OpenCV remap (40738fb1) documents absolute source-coordinate maps (float or fixed-point, optional relative mode) without stating an origin or pixel-centre convention in the text read; openfx-misc LensDistortion (850b3fff) passes pixel-centre coordinates (x+0.5, y+0.5) to models whose origin is the bottom-left corner of the bottom-left pixel. · locator: imgproc.hpp lines 2168-2206 at 40738fb1; Distortion.cpp lines 1079-1090 at 850b3fff; DistortionModel.h lines 179-190 · source: https://github.com/NatronGitHub/openfx-misc/blob/850b3fff65463c073bd64683e5d97a7dec2586c5/Distortion/Distortion.cpp

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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