How do you make transform matrix for Camera resectioning? about dataset_synthesizer

[darwinharianto]

What I found it so far, Matrix for transformation would be
2D = K 3D
because json data is already on camera coordinate frame.

From my test, This holds true for data that has fx,fy,cx,cy = 256,256,256,256
| 256 0 256 0|
| 0 256 256 0|
| 0 0 1 0|

but for data that has fx,fy,cx,cy = 320,320,320,240
| 320 0 320 0|
| 0 320 240 0|
| 0 0 1 0|
this matrix fails.
How do I make the transformation matrix?

[darwinharianto]

I found out I have to make image output have the scale of 2x focal length.
If it is not, the projection would fail.

Any idea how to make a transformation matrix if image pixels doesn't have 2x focal length value?