Cracking glass tool

[revelationsr]

Hi there.

 

With the help of someone on the forum I have been building this tool. It is meant to create a slowmo cracking of a bullet hitting glass. It is looking quite good despite my very low skill with Houdini.

 

I have been having 4 main problems with the setup. I am hoping that I would get some advice. Maybe even some ideas of using different methods.

 

1: optimising the curves.

 

Basically the scene creates a bunch of different random curves. These form the bases of all the cracks. How ever. Since these are random curves they will over lap each other. In order to keep this all one connected curve I need to join two over lapping edges with a shared point. To get around this I use a resample to add tons of extra points. I follow this with a fuse that will snap points together if they are close enough. This works well so far.

 

The issue is the next step. The current method I am using is to put on a polywire. To give the curves some thickness. Followed with a poly reduce to remove extra points. This works but still results in far to many points. If I crank up the reduce any further it starts to make the cracks unstable.

 

Ideally I want to optimise the curves before the polywire. I originally tried using a refine. This how ever results in the removal of points regardless if they are needed to keep edges connected. I get a better result if I use the "snap" method  on the fuse. Refine behaves a lot more like what one would expect. How ever then the polywire does not behave as expected. It seems to create the wire as if all the edges are separate bits.

 

2-3: Creating the surface.

 

Problem 3 might be fixed with problem 2. Because problem 3 is causes by the result of problem 2.

 

I use a divide to create the surface. The "remove shared edges" seems to do the trick. This only seems to work once one of the cracks touches the edge of the glass. I assume it is doing this because it needs to understand the edge loop in order to create the surface. Is there any way of avoiding this? Ideally is there a better way to create the surface? This all seems to be a little to unstable.

 

Problem 3 is that this method results in 1 extra unwanted poly getting created. This poly fills the holes where the cracks are meant to be. This guy needs to be killed. I just don't know how to find and kill it. Because it has a different number every time it gets created for each frame.

 

4: rouge bits.

 

The current method results in small fragments of curves that are not attached to any main curves. These are easy enough to remove after the extrusion because they all seem to extrude in the wrong direction. So I just group them up and kill them. But ideally I would like to avoid them before the extrusion. Any ideas?

 

Cheers

cracks7.hipnc

[revelationsr]

No one has any ideas? Booo

[mestela]

I still reckon rendering the setup as curves, then projecting it onto your surface as a projection map would be the cleanest way; the exact same complexity of the curve layout that makes the cracks look nice will also make it tricky to mesh or boolean.

 

Thinking out loud, if you wanted to continue with the meshed approach, maybe a vdb intersect instead? Might get a little heavy, but my little experiments imply its much more stable than the cookie sop.

 

Rather than cut it right through the mesh, maybe just convert the curves into diamond cross-section tubes, with the cutting edge pointing towards the surface you want to cut, and just have it cut out a groove, like a shallow lino cut?

[revelationsr]

Hello Mestela.

 

I would love to try your ideas out. I just lack to much knowledge. Is it possible to put together a quick little scene to demonstrate your first idea? I like things that are clean

 

Cheers man

[mestela]

Here you go. Like I said, slow.

 

cracks_vdb.hipnc

[revelationsr]

Great will have a look at it very soon. Don't really care if it is slow. So long as it functions I will be happy for now. Cheers man

[mestela]

And a quick displace setup; rendered the cracks directly as curves first from an ortho camera, then use that render as a displacement map on a new clean piece of geo. 

 

To make this look nice you'd want to subtly randomize the width of the curves, maybe even do some comp processing on the curve render, detect when full enclosed shapes are formed and shift their normal to get that sharding effect, work on the shader, lotsa things. Anyway, should give you some ideas.

 

 

cracks_disp.hipnc

Edited October 5, 2015 by mestela