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Manual - Blender 2.4x

[edit] Explode Modifier

[edit] Description

The Explode Modifier is used to alter the mesh geometry (by moving/rotating its faces) in a way that (roughly) tracks underlying emitted particles that makes it look as if the mesh is being exploded (broken apart and pushed outward).

For the Explode Modifier to have a visible effect on the underlying mesh it has to be applied to a mesh which has a particle system on it, in otherwords it has to be a mesh which outputs particles. This is because the particle system on the mesh is what controls how a mesh will be exploded, and therefore without the particle system the mesh wont appear to alter. Also both the number of emitted particles and number of faces determine how granular the Explode Modifier will be. With default settings the more faces and particles the more detailed the mesh exploding will be, because there are more faces and particles to affect detachment/movement of faces.

Here is a link to an Ogg Theora Movie showing a cube with a particle system and Explode Modifier applied:

Here is a link to the original Blender file which has an Exploding cube setup, just free the particle cache by pressing the Free Bake button in the bake panel and then press the Animate button to see the animation:

[edit] Options

• Stacking Order Importance

This modifier is highly affected by its position within the modifier stacking order. If it is applied before a Particle System modifier it will not be affected by particles and therefore appear to do nothing. The Particle System Modifier must appear before the Explode Modifier because the Particle System Modifier has the information needed to drive the Explode Modifier.

Explode Modifier panel with Particle System Modifier above it.

• Protect this vertex group

If a mesh that has an Explode Modifier on it also has vertex groups assigned to it then this field will allow the selection of one of those vertex groups. This will indicate to the Explode Modifier that it should take into account the weight values assigned to areas of the selected vertex group. Then depending on the weights assigned to that vertex group; either completely protect those faces from being affected by the Explode Modifier (which would happen if the faces had a weight value of 1) or completely remove protection from those faces (which would happen if the faces had a weight value 0).

Explode Modifier panel with "Protect this vertex group" field highlighted in yellow.

As well as completely protecting a face (with a weight painting of 1) or completely allowing a face to be exploded (weight painting of 0). It is possible to have in between weight paint values (weight painting values that arn't 0 or 1) that tell the Explode Modifier to only partially effect the underlying mesh.

Below is a plane which has been weight painted in 2 different weight paints, red which represents a weight paint of 1, and blue which represents a weight paint of 0. The reason that weight painting is used is because whenever you weight paint something it automatically makes a new vertex group (if the plane doesn't already have one), which can then be used with the "Protect this vertex group" field.

Weight painted plane before Explode Modifier is run.

Below is the same plane while the Explode Modifier is in the process of exploding the plane. As can be seen the weight painting means that the red (weight paint of 1) faces are left unmodified, and the blue (weight paint of 0) faces are modified.

Remember that by default weight painting makes a vertex group, that is what needs to be selected in the "Protect this vertex group" field for the weight painting to be taken notice of.

Weight painted plane after Explode Modifier is run. Showing the red area unmodified and the blue area exploded.

Here is a link to an Ogg Theora Movie showing a weight painted plane, painted with minimum and maximum weights to be animated with the Explode Modifier:

Here is a link to the original Blender file which the above movie was made from, just free the particle cache by pressing the Free Bake button in the bake panel and then press the Animate button to see the animation:

Below is a plane which has got a blended weight paint on it, with RED being a weight paint of 1 through to other lower weighted colours all the way to BLUE which is a weight paint of 0.

Blended Weight painted plane before the Explode Modifier is run.

Below is the same blended weight painted plane after it has had the Explode Modifier running on it.

Blended weight painted plane after the Explode Modifier is run.

As can be seen the top part of the blended plane is highly affected by the Explode Modifier; whereas, lower down the plane, where the weight painting gets higher in weight, is affected less and less by the Explode Modifier.

Here is a link to an Ogg Theora movie showing a blended weight painted plane, painted with multiple weights animated with the Explode Modifier:

Here is a link to the original Blender file which the above movie was made from, just free the particle cache by pressing the Free Bake button in the bake panel and then press the Animate button to see the animation:

• Clean vertex group edges

This numeric slider field appears to erode the exploded edges around a vertex groups edges (making edges less jaggied). The slider can have a value between 0 (no eroding of edges) and 1 maximum erosion of edges.

The Clean vertex group edges numeric slider field highlighted in yellow.

Below are some screenshots of a mesh that has had an Explode Modifier applied to it with various values for "Clean vertex group edges":

• Refresh (Recalculate faces assigned to particles)

When certain changes are made to the underlying Explode Modifier mesh (such as changing the vertex group weightings of faces) the faces displayed and the particles that influence certain faces can get out of sync. If this happens pressing the Refresh button will tell the Explode Modifier to update all it's calculations to take into account new settings.

Explode Modifier Panel with the Refresh button highlighted in yellow.

As an example, if you have a mesh that has faces that get modified by the end of an Explode Modifier run and you then alter those faces vertex group weights so they have a value of 1 (meaning they can't get altered in future (when the "Protect this vertex group" option is active)) the Explode Modifier will still show the old altered state of the faces until you click the Refresh button.

• Split Edges

When this button is selected faces which are exploded are split making them smaller and more fragmented, giving more faces for the Explode Modifier to work with and usually giving better explode results.

Below are 2 screenshots of a Explode Modifier in progress; one with no Split Edges option active and one with Split Edges activated:

Uvsphere without Split Edges activated on the Explode Modifier.

Uvsphere with Split Edges activated on the Explode Modifier.

• Unborn

This button controls whether mesh faces will be visible or not before a particle for it has been created/born.

Explode Modifier Panel with the Unborn button highlighted in yellow.

What this means for example, is if you have an Explode Modifier on a mesh and certain faces on that mesh do not currently have any created/born particles on them then those faces will not be visible if the Unborn button is not selected, making faces appear to pop into visibility when particles are created/born.

• Alive

This button controls whether mesh faces will be visible or not while a particle for it is Alive/Active.

Explode Modifier Panel with the Alive button highlighted in yellow.

What this means for example, is if you have an Explode Modifier on a mesh and certain faces on that mesh have particles that are Alive/Active on them then those faces will be visible if the Alive button is selected.

• Dead

This button controls whether mesh faces will be visible or not when the particle associated with the face is dead.

Explode Modifier Panel with the Dead button highlighted in yellow.

What this means for example, is if you have an Explode Modifier on a mesh and certain faces on that mesh have particles that are Dead on them then those faces will be visible if the Dead button is selected.

[edit] Examples

[edit] Exploding Cube

[edit] Weight painted object with SplitEdge option not selected

Note that in the image to the right, the faces are not jagged.

[edit] Weight painted object with SplitEdge option selected

Note that in the image to the right, the edges are jagged

[edit] Download .blend file

[edit] See Also

Using the Explode Modifier with a Particle System to break meshes apart

Manual