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A quick guide to dynamic cloth

Discussion in 'Civ3 - Tutorials, Reference, & Guides' started by Plotinus, Aug 23, 2010.

  1. Plotinus

    Plotinus Philosopher Administrator

    Joined:
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    Cornwall
    This is just an outline of the procedure that I've found to be best for adding dynamic elements to units made with Poser. It's a tedious process, but one that can have great effects for swirling capes, cloaks, and coats. I've used dynamic cloth in a few units - such as the Hobbit Burglar, Sherlock Holmes, and Van Helsing, so this is how I did it.

    I'll assume for the purposes of this that you're familiar with what dynamic cloth is, and broadly know how to use it within Poser at least for static images. If not, there are plenty of tutorials for it out there.

    The basic problem with dynamic cloth in Poser is that it won't loop. Say you have a nice fifteen-frame Run animation. You will design it, of course, so that the last frame goes smoothly into the first, because in-game, this will be played on a loop. The same for Attack animations and so on. Unfortunately, if you add a dynamic element to the scene, such as a cloak, you can't guarantee that its appearance in the last frame will run smoothly into the first. The program will animate the cloth realistically from one frame to the next, but not from the last frame to the first.

    So this is what we do.

    First, get your unit into its Default pose. Make perhaps 30 frames of animation, but keep the same pose in all of them, so it doesn't actually move. Now get the thing you want to make into dynamic cloth. It may be a simple Cloth Plane or a custom object. (My Holmes and Van Helsing both use the former, and the Hobbit Burglar the latter - remember you can apply a transparency to a Cloth Plane to get cloaks or capes that aren't square.) Follow one of the many Cloth Room tutorials online to position the object, clothify it, and drape it over your character, over the 30 frames of animation. You will probably want to make it ignore head collisions, so it drapes over the character's shoulders but not his head.

    You may have to create a Constrained Group in the cloth object to ensure it doesn't fall off the character. To do this, position it as closely above the shoulders as possible, and then create the Constrained Group of just a few facets over the shoulder, or the neck. That will hold that point in place as the rest drapes.

    When it's done, scroll through the frames and choose one where you think the cloth looks exactly as you would like it to appear when the character is at rest. Select it and open the Grouping Tool. Click "Create Prop" to create a new prop which is an exact copy of this frame of the cloth object. Close the Grouping Tool. The new prop will probably be in the wrong location, so now move it over your unit so it exactly matches the location of the cloth object.

    When you've got it looking right, open the Key Frames window. Select the new prop in the frame that you're in, and press CTRL-C to copy it. Select the same prop in the first frame, and press CTRL-V to paste it. Close the Key Frames window and go to the first frame of the animation. The new prop should be in place. Delete all of the other frames of animation, so it's only got one frame. And then delete the original cloth object (or, better, make it invisible just in case you need it again).

    The new prop is your Draped Cloth, and it will be the base for the subsequent animations.

    Now the Default animation is easy. Just make the file 15 frames long and do a slight animation to the character. If it doesn't move too much, then the rigid Draped Cloth will look fine. Save this, and maybe render the frames while you're at it. Then you've got them safe. With dynamic cloth, you can't render all the animations in one go as you can with normal units - you will have to render most of the animations individually.

    Now clear the animation by deleting all frames but the first, and then making it a 15-frame animation again. Make a Fidget animation in the normal way. If the character moves very little during this animation, then you can keep the cloth object rigid, as with the Default, and just render it. But I'm assuming that the Fidget is more interesting than this and you need the cloth to move dynamically. Here's the key technique:

    When you have got the animation done to your satisfaction, open the Key Frames window and make everything a key frame - every body part and prop, in every frame. Close the window. Now make the animation four times longer. If it's a 15-frame animation, make it 60 frames. Now open the Key Frames window again. Move the key frames from frame 15 to frame 60. Now move the key frames from frame 14 to frame 56. And so on. You want to end up so that every fourth frame is a key frame - so you have effectively spread your original 15-frame animation out over 60 frames. If you close the Key Frames window and play the animation, it should run very slowly, as if you're watching a slow-motion replay. But otherwise it should be unchanged.

    The reason for doing this is to make the cloth behave more realistically. When you animate dynamic cloth, Poser basically expects the frame rate of the animation to be very fast. This means that with the slower frame rate that most unit animations use, the cloth will appear to float about unrealistically. Making the animation four times as long results in a much more realistic and manageable effect at our frame rates.

    Now clothify the Draped Cloth object. I would use the default settings. Again, you may need to make a Constrained Group to keep in in place on the character, depending on what it is. Run the cloth simulation.

    Now, because the animation is in slow-motion, this should mean that the cloth will have time to respond more quickly to gravity. That is, the movements of the unit will be less jerky, and the cloth shouldn't billow about so much. That means you've got a much better chance of it looping in something like an acceptable way. I would recommend that you design your animation in the first place so that in the last few frames there isn't much movement, or only slow, smooth movement back to the unit's starting position. This should ensure that the cloth has time to stop swinging about or whatever it's doing, and return to something like its starting position. It doesn't have to be precise - just close enough not to look like a terrible leap in game when the animation ends and the Default animation starts again.

    When it looks OK, save the file, and then render every fourth frame. Make sure you render the key frames, not any of the ones in between. Note that you have to do this now, because if you save the file, the cloth simulation is not saved. If you close Poser and then open this file up again later, the cloth object will not be dynamic any more - you will have to clothify it and run the cloth simulation all over again.

    When you're done with the Fidget, do exactly the same thing with the Victory. (I'm assuming you're making both of these animations, although of course they're not obligatory.) Contrary to popular belief, Victory animations should begin and end with the Default pose, just as Fidget ones do. (In game, Victory animations are played straight on from the Default animation, not from the Attack.) So it's the same procedure.

    Now for the attacks. With these, it is best to make a single file to contain the Fortify, Attack A, Attack B (if using), Attack C (if using), and Death animations. This will ensure that the dynamic cloth is smoothly animated from each animation to the next. Design the animations in the normal way. Then expand the whole thing out so it's four times as long, as described above. Finally, clothify the Draped Cloth object and run the cloth simulation, again as described above.

    Now the cloth will progress smoothly from each animation to the next. The only difficulty is the attacks. Will it progress smoothly from the end of Attack A to the start of Attack A? And similarly for B and C? Again, there is no way to ensure this, other than using the method mentioned before of trying to avoid rapid or jerky movement of the character in the closing frames of these animations.

    Save the file and then render every fourth frame, as before.

    Lastly, the Run. Fortunately the Run is played more quickly in-game, so there's no need to do the whole expanding-to-four-times-its-length thing this time. However, when you've got the animation ready, make it four times as long anyway. Say it's 15 frames long - make it 60 frames long. But this time, instead of stretching out the one animation over those 60 frames, copy and paste it three times - so you have the same animation repeated four times in total.

    Now create a Wind Force object in front of the unit, blowing back at it. This is to blow the cloth back behind the character, as if he's running fast.

    Now clothify the Draped Cloth object and run the cloth simulation as usual. The reason we repeated the animation four times was to find two frames fifteen frames apart that look sufficiently similar to look like smooth looping of the cloth. It won't work with frames 1 and 15, but it may work with frames 16 and 30, or indeed with frames 23 and 38. You must just go through the animation and find the best match. When you've done that, render these frames and the ones in between.

    For some units, for the Run you may find it more effective to use not the Draped Cloth object but your original cloth object (the one that you clothified to create the Draped Cloth object itself in the first place). If it's a Superman-style cape, I'd use the original cloth object. In that case you will probably need to create a Constrained Group on the object before doing the cloth simulation (as mentioned above) to stop it just blowing right off.

    If it's more of a coat or cloak that wraps around the character, I'd use the Draped Cloth object.

    Then you're done - at least with the rendering. You may find it necessary to do some postwork - that is, open up some of the frames in a paint program and manually alter the appearance of the cloth to ensure that it loops properly for some of the animations.

    Have fun! Once you get the hang of it, it's not really very tricky - although it is time-consuming and tedious. But you can get some very nice effects this way.
     
  2. Takhisis

    Takhisis Would-be overnight hero

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    up yours!
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  3. LMR

    LMR Back In Green!

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    Thanks a bunch Plot :thumbsup:
     

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