# How would you hide the cracks in cell fracture?

I was watching a video (link to video) video and you could only see the shards where the places have hit the ground, but when I do cell fracture you can see the cracks before they've impacted with anything. I've checked on google and couldn't find anything. Also I want it so that the cracks only show up in the places that have been hit. For example, if a corner of a cube hit the ground then only the cracks in the corner will show and the rest of the cube will remain solid and intact. Watch the video I linked if you don't understand what I'm asking, it could help.

An example of my problem:

I did a cell fracture test with 0 margin but still got cracks where I don't want them (I know it's blurry, I just like my depth of field and motion blur) :

It's the same with a stationary cube with 0 margin which hasn't been hit. You can still see lines where the cracks are.

The examples in the video where it's show without any cracks where it hasn't been hit is in the first scene with the text and in the other seen with the horse. You can see that the top of the text has no lines or cracks until it hits the floor and it's the same with the horses body.

How would you recreate how the fracture in Phymec's video?

Thanks

• You can group the fractured objects and animate the visibility of the group while hiding the original object at the same frame. – Denis Aug 20 '15 at 16:27
• Maybe you should insert a keyframe for the visibility of the cracks at the moment of impact. I dont really know about the cell fracture add on though. – Jonathan Aug 20 '15 at 16:30
• @Denis I'm unsure of what you mean. Do you mean to make the original cube go invisible a frame before it hits something? – Chickenator Aug 20 '15 at 16:32
• Yes, make the original object hidden at the same frame when the fracture objects group made visible, you can animate the visibility with keyframes – Denis Aug 20 '15 at 16:37
• @Denis that half works. It makes it fine at the beginning but that means as soon as the original cube goes invisible the rest of the cracks show and I only want the cracks that have hit the ground to show and no others. What I said might make more sense if you watch the video – Chickenator Aug 20 '15 at 16:39

You could put the unsharded cube in one layer and the shards in another layer:

• by selecting the shards
• using M and click the other layer

(the shards are already put in another layer by default when using the cell fracture)

• Then in the properties panel, in the renderlayers tab you could use keyframes in the exclude section (assuming you use cycles render). Before collision, keyframe in such a way that only the shards-layer is active in the exclude section. After collision, keyframe in such a way that only the unsharded-layer is active in the exclude section. Make sure in the scene section both the layers are active.

But using this exclude method, just must make sure the unsharded cube and shard move in a same way for smooth transition during switching excluded layers

For example, if the collision occurs at frame 100. Then at frame 100, it looks like this: And at frame 101:

To make the cube break more realistically, you could use the Bullet constraint tool https://www.dropbox.com/s/fq3nmhl4b6yyhc3/Bullet_Viewport_Constraints_Tool.zip Select shards, define your Search Radius (100 works ok) and Neighbour limit (10 works ok), and turn on breakable (enable checkbox twice!) and define the breakable value (higher value make it less easy to break).

After you make changes in these variables (while shards selected), then click 'update selected'

• As I said in the other comment, this is half there. If you look in the video when one corner has hit the floor, only the corner shards break off and the rest stays in shape. Doing your method, the whole cube turns into shards instead of just a few. – Chickenator Aug 20 '15 at 17:39
• I updated my answer with the bullet contraint tool to make it break more realistically – Faceb Faceb Aug 20 '15 at 17:49
• In your question you only mentioned about the cracks, you should include what you mentioned in your comment – Faceb Faceb Aug 20 '15 at 17:51
• Thanks I'll edit my question. Also I know bullet constraints making breaking more realistic and makes in break into parts but cracks still show up in unaffected places – Chickenator Aug 20 '15 at 18:21