Shader with displacement on fracturing object?

[slamfunk]

Hey OdForumers,

i'm trying to get a sphere to fracture with vornoi fracture after an impact with a ground plane. The shader that I have applied is displacing the surface of the sphere. As a result, the post fracture pieces look like the edges aren't connected. Any pointers as to how I can get the edges to seal?

Some pieces seem to click in to place after a certain point. (Circled Red below)

Got to start rendering this guy pretty soon so thanks for the advice up front guys.

V

[Macha]

You might have double points there so that if you displace there are two vectors on top of each other, each facing into a different direction, or two vectices closeby are displaced into each other.

[moondeer]

you just need to fuse the points after the fracturing.

a fuseSOP or facetSOP will do that trick.

also, if your workflow will allow, rendering "polygons as subdivision" helps.

Edited February 28, 2012 by moondeer

[lukeiamyourfather]

Displacements for fractured objects should be done by adding 3D noise to point positions with a lookup using the rest position. This will work regardless of whether points are fused or not (coincident points remain coincident points). If displacing along the normal or by any other lookup you'll run into all kinds of issues. If you have a Digital Tutors subscription I cover this in a tutorial (section 8, the last one).

http://www.digitaltutors.com/11/training.php?pid=68

[slamfunk]

Thanks for the replies guys! Really appreciate it.

That's a nice quick fix moondeer. Still getting some artefacts on the edges in certain parts of the animation though. Did you notice any?

Hey Luke, I referred to your tutorial for this too, but I didn't seem to get it to work. Obviously i'm missing some very simple steps. I used an off the shelf mantra surface rather than building it from the ground up. Here is a quick look at what all my vop's are doing, if you have any suggestions for what I could plug in and out.

V

Edited February 28, 2012 by slamfunk

[lukeiamyourfather]

It looks like there's a displacement VOP (displace along normal) in the bottom right which will cause issues when the fractured objects are close to each other. The reason for this is the normals are facing each other on pieces that just fractured, so if you displace based on that the pieces will intersect. By adding noise to the position based on the rest the points move in a "sane" way and won't intersect. This works for some shaders but not all. If you don't want to or can't for some reason create a different shader then try disabling true displacements so it only affects the normals.

Edited February 28, 2012 by lukeiamyourfather

[slamfunk]

Awesome thanks for your swift replies Luke. I ended up using moondeer's method and just tweaked it. With the motion blur it looks good.