General Camera Parameters

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🔍 Parameter Overview:

{
  distortion: new THREE.Vector2(0, 0),       // uK0
  principalPoint: new THREE.Vector2(0, 0),   // uCc
  focalLength: new THREE.Vector2(1, 1),      // uFc
  skew: 0,                                   // uAlpha_c
}

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✅ Definitions and Roles of Each Parameter in Camera Model:

Parameter	Uniform Name	Meaning	Corresponding Item in Camera Matrix
distortion	uK0	The first parameter of radial distortion coefficients (K1, K2...) (e.g., K1 for the $r^2$ term)	N/A (used in distortion function)
principalPoint	uCc	Principal point (image center), in pixels. Typically near the center of the image, e.g., (cx, cy)	Offset terms in the camera intrinsic matrix $(c_x, c_y)$
focalLength	uFc	Focal length, in pixels. Typically $(f_x, f_y)$, related to horizontal/vertical scaling of the image	$f_x, f_y$ in the camera intrinsic matrix
skew	uAlpha_c	Non-orthogonality between pixels, normally 0; non-zero only in cases of special lenses or sensor tilting	Skew term (α) in the camera intrinsic matrix

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📷 Correspondence of Camera Intrinsic Matrix (K):

$$
K =
\begin{bmatrix}
f_x & \alpha & c_x \\
0   & f_y    & c_y \\
0   & 0      & 1
\end{bmatrix}
$$

PS:

• focalLength → $f_x, f_y$
• skew → $\alpha$
• principalPoint → $c_x, c_y$

💡 Retrieving Parameters from Camera Calibration Tools (e.g., OpenCV's cv::calibrateCamera()):

cv::Mat cameraMatrix = [ fx,  skew, cx,
                         0,   fy,   cy,
                         0,   0,     1 ];
cv::Mat distCoeffs = [ k1, k2, p1, p2, k3 ];

• k1, k2 → Correspond to the passed-in uK0
• fx, fy, cx, cy, skew → Correspond to the aforementioned items respectively.