[Import fSpy JSON to Nuke] load a json file with camera data from fSpy into Nuke for single frame camera alignment https://fspy.io/ #fspy #nuke

fspyNukeImporter.py

import json
import nuke

def Matrix4toList(M):
    mVals = []
    for i in range(len(M)):
        mVals.append(M[i])
    return mVals

# ---  load file  ---
fp = nuke.getFilename("Select fSpy data file", "*.json")

with open(fp) as datafile:
    data = json.load(datafile)

# ---  create camera, set knobs
camera = nuke.createNode("Camera")


# camera transform
M = nuke.math.Matrix4()  # camera pose
matrixVals = data["cameraTransform"]["rows"]
for row, values in enumerate(matrixVals):
    rowStart = row * 4
    M[rowStart + 0] = values[0]
    M[rowStart + 1] = values[1]
    M[rowStart + 2] = values[2]
    M[rowStart + 3] = values[3]

camera["useMatrix"].setValue(True)
camera["matrix"].setValue(Matrix4toList(M))


# projection parameters
aspectRatio = float(data["imageWidth"]) / float(data["imageHeight"])
camera["vaperture"].setExpression("haperture / {aspect}".format(aspect=aspectRatio))
camera["focal"].setExpression("haperture / (2 * tan({hFOV} / 2))".format(hFOV=data["horizontalFieldOfView"]))

principal = data["principalPoint"]
camera["win_translate"].setValue([principal["x"], principal["y"]])