VFX / Dynamic Paint Procedural Cracking

Let's take a look at one way we could do a procedural cracking in Blender. I have probably written a similar technique in the past, using Dynamic Paint, but nevertheless, you may learn a thing or two.

NOTE: This is not a tutorial on how to fracture or break an object, it is more like a cracking like you see on the ground during earthquake or iceberg kind of crack.

It would be easier if you have some understanding on:

• Cell Fracture
• Dynamic Paint
• Particles
• Vertex Weight

This is not very difficult to setup though. I am going to write down the process first and if I have time I will create a quick video tutorial.

1. FRACTURE PRE-PROCESSING

It is very likely that you will fracture the mesh object before applying any dynamics. You want an object to crack or break in certain way. So this is what we are going to do first.


You can use any mesh, you simply apply Cell Fracture using any setting you like. If you have no clue how to use Cell Fracture, please read previous post, watch video tutorial by Daniel Kreuter:
http://blendersushi.blogspot.com.au/2012/07/vfx-blender-fracturing-with-daniel.html

I will just use a plane with thickness:

I will fracture this mesh using Points that are based on Particles (Volume). So I emit some random Particles, around 200 of them all over this mesh.

Then, I apply Cell Fracture, with setting like below: (I do not want any gap between fracture, just zero the margin, everything else is at default)

My guess, the Cell Fracture does something clever in the background, calculating Voronoi pattern based on Points you provided, and then Boolean of some sort, and you end up with fracture objects or shards.

I get something like below, this is our pre-made fractures.

Layer 2 should contains the shattered mesh. Layer 1 should contain the original mesh.

If you want to explode the object using real Blender dynamic, feel free. You can get Blender built with Bullet Physics, or wait till it is out officially. Or you can do it just by using Blender Game Engine.

But that is not what we are trying to do. Maybe that is for next time.

2. Dynamic Paint and other Modifiers
We will apply some kind of Dynamic Paint and Vertex Weight to Influence our Mesh.

For our purpose, we will JOIN the shattered mesh back into one piece. Select all the shards, and press CTRL+J to join them. If it does not work, try selecting few pieces, then CTRL+J, then select other pieces and CTRL+J again until you have a single mesh object.

Now what?

Turn this object into Dynamic Paint CANVAS. Switch the option to Weight. This will allow you to dynamically Paint Vertex Weight into the mesh.

Ok, next, you create Dynamic Paint Brush. You can use any mesh object or even Particles, and simply switch on the Dynamic Paint Brush for that mesh.

I will use some Poly Cubes as Dynamic Paint Brush, I will turn them into Wire object and make sure they are not renderable.

Now, the last thing you do is just to apply Modifier that accept Vertex Weight. For our cracking purpose, simply use Smooth Modifier, it will do the job:

WATCH OUT: Dynamic Paint Modifier needs to be on the top of other Modifier (because Blender modifier stacking rules), this is one modifier that dynamically paint Vertex Weight to pass on to any other Modifiers that accept Vertex Weight.

Now look at your 3D scene, you have Procedural Cracking already happening. Wherever you put your Dynamic Paint brush(es) to paint Vertex Weight, it is going to crack.

The effect is LIVE and you can keyframe it manually.

LIVE Feedback.

Manual animation.

That is one way to do a procedural cracking in Blender.

GREASE PENCIL x CELL FRACTURE x DYNAMIC PAINT x MOTION PATH
You can try something that is more interesting and procedural, using the Grease Pencil and Motion Path. Very handy for a single crack.

BLENDER BULLET IT, MAYBE...
When Blender Bullet Dynamics is out officially, you can do a lot better "earthquake" type of cracking, fracturing and whatnot, with a real physical ground that is dynamically pushing the fractured shards mesh.

The process is similar, you just need additional setup for dynamics. You still need to setup the fractures in advance. Then you setup some real dynamics to give the cracking and to push the fractures/shards.

Maybe you layer some smaller shards that you emit from Particles, when it hits.

Keep eyes on:

• Blender Bullet Pyhsics
• Blender Particle Nodes

But you know, as you got more power, things will get more complex and complicated too....

CRACKING WITH BRANCHES
If you want to animate cracking with branches, you can draw the crack lines using mesh edges, point by point on mesh surface and just let it run this way:
1. Draw Edges and Branching + Build Modifier + Skin Modifier (cool!) + Dynamic Paint
2. Draw Edges, Emit Particles from Vertex + Dynamic Paint Particles --> this one is cooler (more control) and the effect looks really good.

You can do even more procedural Dynamic Paint (Brush) Cracking like this:

1. Activate Blender Ivy Gen (inside the Add-On)
2. Create Ivy Gen Curves and let it run across surface of your mesh.
3. Convert Curve into "mesh" object.
4. Emit Particles from each Points
5. Apply Dynamic Paint Brush to this object.

ALTERNATIVE: Easy Boolean and Skin Modifier Cracking