Cornerpin without reference points

Using Mocha AE plugin v6.1.3 on an old, black and white shot of a building I-beam being raised on cables (don’t ask). After a lot of work, think I got a reasonably solid track based on the purple grid. But now comes the problem.

I need to attach a logo to the bottom of the beam. However, none of my Google searches have turned up how to attach a shape via cornerpin when you don’t have reference points. I used the corners of the beam to adjust the track, but that makes the logo match the size/shape of the beam (there’s also the issue of the edge angles twisting as the beam moves but one problem at a time). I tried just using Transform data which isn’t awful but clearly isn’t right due to the Y-axis swing of the beam. I can’t find how to correctly set Surface corners that won’t distort the logo without reference corners in the footage.

I can’t show the footage but here’s a quick trace of what the final result should be and where I believe the Surface corners should be. I’m not a Mocha whiz by any stretch so maybe I’m overlooking something very fundamental.
i-beam

Just align the edges of the surface tool and not the corners? Try that and let me know.

Mary, thanks for the response. I’m trying that now but (stupid question coming in) how do I know the correct position for the edges so the logo isn’t ultimately distorted by the corner pin? Top edge to the bottom of the beam, sure, but then how to know where to put the left, right, and bottom edges so the logo maintains its correct proportions? Do I use the logo as the Insert Clip source and just eyeball it until it looks right? Maybe I made too many adjustments to my track and Surface–again, it was a tough track with old, black and white, very noisy footage–but doing this edge approach I just can’t keep the corners stable and relative to their start position/each other so the logo doesn’t look like it’s twisting on its own rather than a rigid piece moving with the beam.

I’d try to really nail it with adjust track (not sure if you have yet?). If the surface isn’t sticking like glue then the track needs work.

I’d just eyeball it for proportion or you can use Mocha Pro and set the insert aspect ratio.

Actually it appears to be sticking really well, except the corners. Maybe my workflow is flawed: I finally managed to get a decent track then went into Adjust Track to fine-tune. Lacking any other reference points, I set my Surface corners to the corners of the I-beam, which again, is moving at least partially in all three axes. If the Surface corners drifted, I nudged them back to the I-beam corners, which may not be the smart play since the beam is both twisting and rocking. But at the end, I got things sticking with maybe 10 keyframes. But then I ran into the issue of not knowing where to set my Surface corners so as to not distort the logo, and the edges twisting since I was using a non-stable plane as reference.

Is corner pinning just not a viable approach here? Again, Transform doesn’t look bad, just could look better because of the perspective shift

Can you show me? I am just not picturing it.

Thank you for taking the time to help with this. Greatly appreciated. Sadly, I can’t post the clip here but think I’m safe showing a small section of it as a still, roughly 70 frames in. Top, you can see the right edge of the I-beam and see that it’s twisting, meaning the top corner appears further left than the bottom corner. Bottom, you can see the purple grid overlay grid. Again, it moves along quite well with the I-beam, but the edge perspective seems far more extreme than the beam would account for. And when I try to extend the Surface out to be where I want the corners of the logo to ultimately be (which is a lot more eyeballing and guesswork than I like) the logo edges seem to twist of their own accord rather than being a flat plane moving with the beam.

Also included screenshot of the reference corners from the same point (bottom is drifting slightly here but not enough to throw off the results). Again, maybe not the best points for reference since the beam moves in all three axes, but the only points available.

Does that help?
angle

Honestly, that might be because the area to track is so small there’s some pixel variation. I think you’d really have to tweak everything in the extreme with adjust track to get it 100% correct.

Mocha doesn’t do well with very low resolutions, it needs the texture to track perfectly.

Thanks for all your help! Took some serious eyeballing and keyframing but think I got it close enough for our needs. Now to go explain to my producer in no uncertain terms to never, ever give me a shot like that again.

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Tell your producer the shot was a breeze and that you thoroughly enjoyed working on it. with a box of donuts. keep the money train flowing :slight_smile: