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Thread: Surgery showing scalpel cutting flesh. Suggestions on how to accomplish this?

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    Surgery showing scalpel cutting flesh. Suggestions on how to accomplish this?

    I have to create a medical animation of a cholesteatoma surgery - like the one here https://www.youtube.com/watch?v=Nelh-dig6a8

    I have an ear model I've been working on from a scanned head. What I'm having trouble with is modeling the incision to show the scalpel cutting into the flesh. I've reduced the polygon count on the ear model so that I could make it a subpatch model. I picked an edge to use as the incision, but if I try to model the interior, the incision pulls apart when I turn on subpatches. Without the interior modeled I can use cloth dynamics and the sewing function to make the cut, but it doesn't look right because the skin has no thickness.

    Click image for larger version. 

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    So, I need some sort of work around solution. Morph target? or faking the cut?
    I've been told it would be okay to dissolve to the opened incision as shown in the video above.

    Thanks!

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    Quote Originally Posted by Spaceboy64 View Post
    but if I try to model the interior, the incision pulls apart when I turn on subpatches.
    You need to extend edges by very small offset, then extend again by small offset (eventually yet again). So basically making polys with +-90 degrees between them in sub-patches.
    Experiment with simple box, if you're not familiar, and turn sub-patches and try making box to have straight walls.
    http://lightwiki.com/wiki/Fundamenta...ing_Part_Three
    Last edited by Sensei; 02-06-2015 at 05:02 PM.

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    Thanks. I know I can do that, but it makes the model unnecessarily complicated, and still may not look like an uncut surface. Also, the cloth dynamics sewing function doesn't work that way. (I'll probably have to abandon using that anyway though). Now I'm leaning towards making it look like a cut without actually cutting geometry. I know I'm not the first person to have an assignment like this. There's got to be a way.

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    skeptic lertola2's Avatar
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    I would use morphs. That way you can model your skin thickness. To get a sharp corner on your subpatch incision you need to separate the outside of the skin from the inside thickness. The two sides of the shape will form a sharp edge if the cut out side of the skin and the cut face are not welded together. In the attached gif you can see that the object on the right has a sharp edge on the incision because I cut the pink part out then pasted it back in so it is not joined to the outer part.

    You can also use nodes to animate the morph over time. In the attached scene two nulls are animated to control the opening of the morph.

    How do you get rid of the visible seam where the opening is going to happen? I don't know of a good way to do that with Lightwave. If I were doing this job I would do a separate render of an object without the seam and blend the two renders it together in Aftereffects.

    You might also be able to add another morph that moves the closed seam down and use that to get a tugging effect as the knife cuts into the skin.




    incision.zip

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    Thank you very much! That's very helpful. I will try that out. I don't have much experience with nodes but I'll give it a shot. I've used a null to control a morph before, but not using nodes.
    I was thinking of a technique used to make tire tracks in sand that's been around for quite some time. I've forgotten exactly how that was done, but it involved covering and revealing the tracks as the vehicle moved.

    Thanks!

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    RETROGRADER prometheus's Avatar
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    clothFx and sew tool perhaps? and use cut by event? I havenīt tested though.

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    Thanks. I tried that, as I posted above, but that only works if the surface has no thickness. I am going with multiple morph targets, and then separating the subdermal layers as suggested above. So far it's looking good and I have also modeled an endomorph with the incision pulled apart and ear folded back. Looking at the actual surgery you can see that the skin doesn't pull apart all that much at first, then blood starts to come out. Also, this doesn't need to look totally realistic because it's for illustration purposes, but I think I'm on the right track now.
    Thanks.

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    lertola2, I used your morph set up and it worked great. I used a copy of the ear object with the cut points welded and clip map attached to my scalpel to reveal the cut, which looks good.

    I have another question though. I tried to use the same set up with the surgical drill cutting the tumor away, but it's not working very well. I would like to turn the morph on as the drill passes near, and then stay that way. My drill object moves around the tumor, so the simple Y axis position isn't what I want. I don't understand the node system well enough. Could you tell me how I might set this up so that the drill looks like it's cutting the tumor out?

    Here is the animation as it is. Just cutting: http://youtu.be/bR_-5KYccFk
    and the whole thing: https://www.youtube.com/watch?v=SK1mgb_7QEc (needs surface adjustments)

    Thanks!

  9. #9
    Registered User Slartibartfast's Avatar
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    animated morph with DPKit markerpen:



    Scenefile:

    surgery.zip

    Good luck with the surgery now

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    Thanks, but I already figured out a way, using this method https://www.youtube.com/watch?v=vYUM7Vg3Bvw
    It doesn't stay in place, but the flesh moves when the instrument goes in and moves around. I also added a particle emitter to the end of the drill bit so it throws off droplets.

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    Registered User zardoz's Avatar
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    here you might find some more tips, thanks to probiner for giving me the link
    http://forums.newtek.com/showthread....=1#post1182059
    Intel Core i7-4770 @3.40GHz,GeForce GTX 660 - Ram 8Gb - Win 8.1 64b

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    Thanks for all the helpful suggestions!

    Here is the finished animation, at least until I get feedback from the client.
    https://www.youtube.com/watch?v=nnsKtczkYlI

    I used normal displacement attached to the tip of the drill, so that when the drill goes in, it moves the flesh around and looks like it's actually doing something. I also added a particle emitter to the drill bit, which is spinning.

    Please let me know what you think.

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