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Bag of goop...


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Well, it works!

 

Is it just me or does this look like a good ole bag o' goop?

 

Still needs tweaking for its final use of course... I like it!

 

I used a boolean... here is the set up..

 

Plastic bag mesh. Duplicate bag mesh slightly smaller (bag is transparent... need some air between goop and bag to avoid the transparency artifacts when surfaces are too close. Also avoids accidental pass through of the goop outside of the bag).

 

A box like mesh above the goop shape. Assign box shape to boolean bone. Assign plastic bag to a child of boolean bone so it won't get... booleaned.

 

I then use two different groups and material settings. The boolean shape has a lighter color with a bump. This would then be the surface of the goop inside the bag but not touching it. The main goop shape gets a darker color with out the bump (there would be no bump since it is conformed to the bag. The bag has its own bump).

 

This worked great... but I took it a step further. I was getting a perfectly flat surface across the top of the goop with the boolean... I didn't like it.

 

So I added more splines to the boolean shape and and added slightly curved edges, lining it up as close as possible to the edge of the goop where it touched the bag. It was not perfect since the boolean shape is boxy... but close enough to work.

 

What this gives me is a slightly curved edge to the goop, like surface tension, which catches the light for a nifty specular highlight right along the edge of the goop as it touches the bag.

 

Vernon "Big fat goop monkey" Zehr

goop.jpg

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I barely understood anything from your explenation(I have an excuse! I've been using AM for 3 weeks :P), but I have to say one thing: WOW! :D it look so darn GREAT!

 

EDIT: I just noticed something... it might just be my eyes, but I keep seeing a blue shine on the top left side of the holy "bag o' goop". then again, I might be crazy and I might see blue shine everywhere

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Thanks Joakim!

 

Yes, there is a slight blue cast to the plastic bag. It is mostly white with just a hint of blue. I actually studied the type of plastic I was trying to simulate. It has a ghostly bluish cast.

 

The blue becomes more pronounced at that corner because I have set a fairly high density on the transparency of the plastic. I also have a great big dome with a bluish image and a skycast material on it for reflections in my scene. There is just a tiny hint of reflectivity (5%) in the plastic so it will probably be picking up some of the dome.

 

Density will cause the transparency to "thicken" the further away something is, it will become more solid, and show more of the color of the group. The bluish tint in the upper corner is more pronounced since you are seeing more plastic at that angle and there is less goop.

 

Since the goop is practically touching the bag at the base, the density doesn't have as much effect. I used the density so that I get that thickening where the bag is sealed, without it the bag becomes very cellophaney... too clear.

 

Keep playing with AM. You will get the hang of it someday. Of all the cool things I have done over the years, this is probably the easiest with the coolest result.

 

p.s. if you see a blue shine everywhere you are taking too much viagra.

 

Vernon "!" Zehr

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I will kill two birds with one stone here... well, two questions answered anyway...

 

I know, I know, it is called "Animation" Master but...

 

...this bag of goop will not be animated. It is for a still image. If it ever needs to be animated, that will have to be addressed separately I think. Should be a fairly easy matter of moving and rotating the boolean bone I think. I would have to make the boolean shape larger to make sure it encompasses the goop shape.

 

As for what the goop really is... uh... you will just have to wait and see! It is a surprise!

 

thanks for all the comments, those that have been... and those that will be... I will definately take them all into consideration as I perfect my goop.

 

Vernon "Happy Gooping!" Zehr

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Vern,

That is some innovative use of boolean cutters!

Looks like nothing I've seen created in A:M to date.

 

I'm looking forward to any further information or images concerning the technique you use. One never knows when you might need a bag o goop. :)

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I tried a new version of this technique with out any success.

 

The basic concept is this...

 

A "goop" shaped cylindrical tube... with thickness. Like an extruded doughnut. Bag shape "inside" extruded and wrapped outwards. To create sort of like a mold. Then put stuff inside which gets cut away by this boolean "mold"

 

What happens is that the transparent bag (not booleaned, child bone) is fine, but the goop shape which is now just a block inside the bag shaped "tube" becomes invisible where there is "overlap" of the boolean shape. Where the double/quadrupled surface of the mesh in the view plane overlaps... the shape inside becomes totaly removed... rather than picking up the texture of the boolean as in the original example.

 

Hard to explain. Needless to say, it just doesn't work. I am still playing around with the technique.

 

The other way works fine. I will stick with it for now. Will post some screen grabs later of the technique. It is really simpler than it sounds.

 

Vernon "Is that a boolean or are you just happy to see me?" Zehr

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Well,

 

I threw this together to show the process. Hope it makes some sense. It is kind of hard to show it what with all the hidden shapes and transparency.

 

On the left is the pws showing the groups and bones. The key thing is that the plastic bag is assigned to the "dont_cut_me" bone which is a child of the boolean cutter bone. The big green boxy shape is assigned to that. The goop shape is just left unassigned to any bone or the model bone. It could be assigned to another bone as long as it is not in the same hiearchy as the boolean cutter... this info is more for people who are not familiar with booleans.

 

Let me know if you need to see more.

 

Vernon "Don't cut me!" Zehr

boolean_tutorial.gif

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Need some more help if possible...

 

I would like to have a material for the goop that is sort of "thickish" (opaquish) in appearence, with some globular particles floating in it.

 

Can't use blobbies... for some reason they won't show through the boolean cutter. It sort of eliminates it... or maybe they don't show through the transparent goop... either way blobbies don't seem to work... I could be doing it wrong... or my version of AM is too "old".

 

I have not tried spriticles yet... I just kind of figured I would get the same result.

 

I seem to recall that someone created an example of this, I am just having trouble finding it.

 

thanks for any guidance.

 

Vernon "Very Thickish" Zehr

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Unfortunately no... need it now.

 

I think I am just going to use a bunch o' little meshes and scatter them around. Using 8 patch sphere shapes and distorting them into a bunch of amorphous globs should do the trick... only need about 50 or so...phew...

 

I tried animating this technique using John's project file... it won't work!!!!

 

I posted a more thorough explanation to the general forum if anyone is interested.

 

Has to do with booleans and dynamic chains. Can't have a booleaned chain of bones.

 

Vernon "Globs of goop" Zehr

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WooHooo!!

 

It jiggles!

 

I figured out how to work around the animation difficulties. It can be animated...

 

All the dynamics and rigging is based on Johnl3D's goo bag project in the wip section. Thanks John!

 

I created two separate models.

 

Model 1: Dynamic Bag

This model is just the plastic bag with a dynamic constraint at the top of the bone chain. Very straight forward.

 

Model 2: Dynamic Goop

This model is the goop shape and the boolean cutter. The exact same set of bones used in the first model are used for the goop. the bones absolutely muct be identical in size position etc.

 

The boolean bone in this model is positioned at the same point as one of the bones in the goop shape towards the top of the bag (5 bones, aligned to number 4).

 

Poses

One on/off pose the same for both. One dynamic constraint on the last bone in the chain.

 

Choreography set up

I added the goop model first. Just easier to work with out the other model exactly on top of it.

I make whatever adjustments to the model position...etc (keep track of this exactly... need it to be the same for the other model).

 

The model is horizontal so I had to rotate the base bone 90 degrees on the first frame. I then add a constraint to the boolean bone to translate to the 4th dynamic bone (the one it is aligned with in the model).

 

Step through the dynamic simulation and adjust the translate offsets and rotation of the boolean bone to simulate the "air bubble" sloshing around inside the bag. Once this is done I add the plastic bag model and set it in the exact position as the goop model.

 

Attached is the sample movie that I did very quickly.

 

I tried to slosh the bubble back and forth at the end... not enough frames so it looks very jittery.

 

Improvements

I think I should be able to come up with a constraint set up that will allow the boolean bone to follow the motion with out the need for so much hand animation on it. That is the only problem right now. To much effort to get the boolean to maintain realistic motion and volume to represent the air bubble.

 

I can provide a project file if anyone is interested.

 

 

Vernon "Don't spill the goop" Zehr

 

(edit: I did a new improved render. I think it looks a little better.)

goop2.mov

Edited by heyvern
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