Blackmagic Forum

I have a video clip of an airplane flying over a city. I've mapped the clip to 3D, so I have all the points I need. Now I'm trying to map text to the ground. I'm finding it is virtually impossible to get the text to move properly—i.e., as if it's painted on the ground. Anyone have any tips on how to do this? I realize putting the ground plane in the right place and the aligning the text with that could help, but that poses the same exact problem.

On a separate note, when I tip the text over so it's "lying" on the ground, it doesn't get narrower at the top, as if it has converging lines. The top of the text should converge, since it's "farther away" from the camera. What's going on there? This should be very obvious, as the text is in a parking lot and it's easy to compare with the converging lines of the parking spots.

For alignment you should use the solved points in 3D, these give you locations in 3D scene to place your geo. Visually, if your object is above ground it moves too fast, if it is below, it lags behind (when camera moves forward).

If perspective doesn't match your solve is probably off with wrong lens FOV. Check that the value makes sense in relation to filmback size. It doesn't have to match what is written on lens as those numbers aren't accurate but it should be in the ballpark at least.

I often use this technique to place stuff in 3D space where I want them:

Follow the steps, make 2-3 points on your ground for position and rotation and it will stick nicely

Thanks for the tips, folks. I appreciate it. Hopefully, the more I do it, the easier it'll get. I'll have to give what he shows in that video a shot. May need to watch it a couple more times, though.