The 9/11 Forum

As with the recent Flight 175 rotoscope modeling process, I thought it would be useful to generate similar orientation/time data for the WTC 1 cap descent.

The end result should be a pretty accurate series of positional and angular changes in three dimensions, against time.

I'm not sure if separate studies have been performed, and would be interested to see them posted here.

This is the first PRE-DRAFT test:


http://www.youtube.com/watch?v=IgUOscyCr9k

(I'm aware of the 'jolt' in the rendered descent in the extended YT copy. It shouldn't be there. Only noticed it after the render and didn't want to wait another 4 hours to re-do it. It's just a pre-draft test to get the idea across at the moment. Accuracy will improve massively over time.)

One point of note at this very early stage, is that in order to replicate the initial 'tipping' I had to set the pivot point to the front of the North Face. Without doing so there is an unavoidable vertical elevation of the 'split-point' in the North face. An obvious observation perhaps, but thought it should be noted. The pivot point is bound to move towards the core as accuracy is increased, as some of the vertical motion caused by tipping will be counterracted by physical vertical motion of the entire cap. Hope that makes sense

Camera positions for various clips would be very useful...

Anyone interested in me progressing this process ?

One purpose I was thinking of would be to identify the relative 'overlap' between the initial descending caps for both WTC 1 & 2 to determine the relative amounts of crush-up and crush-down implied. I think that it would be especially informative for WTC 2.

youtube wants me to log in with an account to see the video.
that's a first. you didn't slip some frames of T & A in there, did you?

femr2 wrote:Anyone interested in me progressing this process ?

Yes.

Femr, yes.

I like your visuals because they allow us to see past the smoke. The smoke is the only thing which obscures the near simultaneous failures of the north and west perimeters. Already in the OP visuals we both walls fail along straight lines. This happens with with no observed buckling, the upper sheet sliding over the lower.

The cause of this sheet ejection has no know mechanism. Most all of us can visualize a mechanism in which the upper sheets are pulled inwards and fall inside the lower sheet. We all know how early core failure can bow the exterior inwards. But how do you kick perimeter sheets outwards through natural failure?

Your visuals will also be excellent in the study of possible small jolts and their causes, developing on the other thread.

newton wrote:youtube wants me to log in with an account to see the video.
that's a first. you didn't slip some frames of T & A in there, did you?

I had it set to private for some reason Fixed.

Major_Tom wrote:Femr, yes.

I like your visuals because they allow us to see past the smoke. The smoke is the only thing which obscures the near simultaneous failures of the north and west perimeters. Already in the OP visuals we both walls fail along straight lines. This happens with with no observed buckling, the upper sheet sliding over the lower.

I'm hoping that any deformation of the actual cap (from square) will show up as part of the process.

The cause of this sheet ejection has no know mechanism. Most all of us can visualize a mechanism in which the upper sheets are pulled inwards and fall inside the lower sheet. We all know how early core failure can bow the exterior inwards. But how do you kick perimeter sheets outwards through natural failure?

Could early core failure cause *bulging* ?

Your visuals will also be excellent in the study of possible small jolts and their causes, developing on the other thread.

I've had a bit of a rethink on how to actually perform the rotoscope...

The test above was done manually in 3D Studio, but I'm thinking that if I improve the fidelity of the model I use in the spreadsheet simulations (which gives me total code control over position/time..pinpoint accuracy), and plug-in the vertical displacement datasets from the Sauret footage (with the addition of perspective correction) then we'll have not only vertical but rotational data to work with, and it should match-up perfectly. Any visual differences between actual cap position and rendered cap position may then point to additional deformation of the cap, errors in the datasets, errors in perspective correction, errors in tilt and rotational data, ....all of which can then be improved and hopefully new surprises fall out of the bottom...

femr2 wrote:Could early core failure cause *bulging* ?

Well, many things can happen when you remove primary structural supporting elements in a simple frame structure, e.g. columns, so that a sub-assembly of elements above displaces/rotates and secondary elements, e.g. horizontal floor trusses fail in the upper part, e.g: