kitti数据集相机投影矩阵 | kitti数据集相机投影矩阵

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问题描述

我正在查看kitti数据集，尤其是如何将世界点转换为图像坐标。我看了一下README，并在下面说，我需要先转换为相机坐标，然后再乘以投影矩阵。我有2个问题，来自非计算机视觉背景

I am looking at the kitti dataset and particularly how to convert a world point into the image coordinates. I looked at the README and it says below that I need to transform to camera coordinates first then multiply by the projection matrix. I have 2 questions, coming from a non computer vision background

我查看了calib.txt中的数字，尤其是矩阵为3x4在最后一列中具有非零值。我一直以为这个矩阵 = K [I | 0] ，其中K是相机的固有矩阵。那么，为什么最后一列非零，这意味着什么呢？例如P2是

I looked at the numbers from calib.txt and in particular the matrix is 3x4 with non-zero values in the last column. I always thought this matrix = K[I|0], where K is the camera's intrinsic matrix. So, why is the last column non-zero and what does it mean? e.g P2 is

array([[7.070912e+02, 0.000000e+00, 6.018873e+02, 4.688783e+01],
       [0.000000e+00, 7.070912e+02, 1.831104e+02, 1.178601e-01],
       [0.000000e+00, 0.000000e+00, 1.000000e+00, 6.203223e-03]])

将投影应用于[u，v，w]并将u，v除以w之后，这些值是相对于图像中心处的原点而言的还是原点在图片的左上方？

自述文件：

README:

  x = Pi * Tr * X

推荐答案

对于所有P矩阵（3x4），它们表示：

For all the P matrices (3x4), they represent:

P(i)rect = [[fu 0  cx  -fu*bx],
            [0  fv  cy -fv*by],
            [0   0   1  0]]

最后一列是基线，以米为单位参考相机0。您可以在最后一列中看到P0都为零，因为它是参考相机。

Last column are baselines in meters w.r.t. the reference camera 0. You can see the P0 has all zeros in the last column because it is the reference camera.

这篇文章有更多详细信息：

This post has more details:How Kitti calibration matrix was calculated?

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