Explaining poses.txt

[schurist]

Hi,

first of all, thanks for this comprehensive demonstration of TSDF!

I am struggling a bit to understand the pose.txt files. Could you explain the transformation matrix from the *.pose.txt files in greater detail?

My assumption is that these 4x4 matrices correspond to the viewpoint transformation, so they represent the transformation from world coordinates to camera view coordinates for each frame?

If this is the case, I would have another question:

I have a set of frames and corresponding depth maps as png files. For each frame I estimated the camera pose using COLMAP, which uses SfM to calculate the correspondence points and estimate the camera position.
The output of the COLMAP reconstruction is the following:

The reconstructed pose of an image is specified as the projection from world to the camera coordinate system of an image using a quaternion (QW, QX, QY, QZ) and a translation vector (TX, TY, TZ). The quaternion is defined using the Hamilton convention, which is, for example, also used by the Eigen library. The coordinates of the projection/camera center are given by -R^t * T, where R^t is the inverse/transpose of the 3x3 rotation matrix composed from the quaternion and T is the translation vector. The local camera coordinate system of an image is defined in a way that the X axis points to the right, the Y axis to the bottom, and the Z axis to the front as seen from the image source.

So by extracting the 3x3 rotation matrix from the quaternion and concatenating it with the translation vector (TX, TY, TZ) I should get the desired 4x4 matrix, correct?

Maybe I am misinterpreting something, because unfortunately my reconstructed results do not look reasonable.

[yyxr75]

What does it look like? Give us a pic

[YJonmo]

I am having the same problem. I have simulated data which I get them from Blender with corresponding matrix_world for the camera for every frame. But using this tool box I cannot reconstruct the same point cloud that I see in the Blender. It just shows a mess.

The Blender camera matrix_world is a 3*3 plus the 4rth column being the translation of x, y and z.

[zParquet]

Just for reference: I use the pose of the replica dataset to obtain the correct results without any transformation.