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Manual - Blender 2.4x

[edit] Particle Instance Modifier

[edit] Description

When a Particle Instance Modifier is added to an object, that object will be used as a particle shape on an object which has a particle system associated with it. This means that to use this Modifier you must also have another object which has a particle system on it, otherwise the Particle Instance Modifier will appear to do nothing.

Particle system on Left has no Particle Instance Modifier object associated with it. The one on the Right is associated with Cube shown by using a Particle Instance Modifier on the Cube

[edit] Definitions/Terms

Here is a brief explanation of the various terms and definition used in relation to particles and the Particle Instance Modifier:

• Particle System - Is an object/mesh which has the ability to emit/generate particles activated on it.
• Normal Particle - Is a particle that is not a Children/Child generated particle type.
• Children/Child Particle - Is a particle type that is generated and placed with relation to other Normal particles that already exist. Children/Child particle are generally much quicker to calculate.
• Unborn Particle - Is a particle which has not yet been displayed/emitted because it is not its time to be emitted/displayed. One of the reasons a particle can be in Unborn state is that it is before the frame at which it is to be emitted.
• Alive Particle - Is a particle which has been displayed/emitted and has not yet reached its Dead state. One of the reasons a particle can be in an Alive state is that it has been Alive for less Frames than its life length.
• Dead Particle - Is a particle which has been displayed/emitted and has reached its end of life length and at that point it enters the Dead state.

[edit] Options

Because of the co-dependant way in which the Particle Instance Modifier is influenced by the underlying Particle Systems on other objects, some of the apparent effects generated by the Particle Instance Modifier can look and act vastly different, depending on the underlying settings of the Particle Systems it is associated with. This is worth taking account of if the Particle Instance Modifier settings don't appear to be giving the results expected, as it may indicate that the Particle System settings may need altering rather than the Particle Instance Modifier settings.

Particle Instance Modifier Panel

• Ob:

The Ob: field (short of Object), associates this Particle Instance Modifier with another object (usually the other object is the name of an object which has a Particle System associated with it). This indicates that when the object named in this field emits particles, those particles will have the mesh shape of the current Particle Instance Modifier's mesh.

If for example a sphere has a Particle Instance Modifier added to it, when the Ob: field of that Particle Instance Modifier is filled in with the name of an object that emits particles, those particle will be sphere shaped because the object that had a Particle Instance Modifier added to it was a sphere shaped object.

Particle Instance Modifier Panel - With the Ob: field highlighted in yellow.

Even though most of the time the Ob: field will have the name of a object which has a particle system entered into it, it is not mandatory you can enter an object which does not have a particle system and it will be accepted by the Ob: field, as there do not appear to be any checks made to make sure the object name entered into the Ob: field is valid.

• PSYS:

The PSYS: field (short of Particle System), is used to select which Particle System number to apply the Particle Instance Modifier to, when the mesh which has the Particle System on it has more than one Particle System on it. The PSYS: field can have a value between 1 and 10. It is possible to select any of the 10 Particle System numbers, however a check will NOT be made with the underlying particle emitting object specified previously in the Ob: field. If you select a Particle System number which does not exist on the particle emitting object, then the particles on the emitting mesh will keep their normal particle shapes no warning will be given that the chosen Particle System does not exist on a particular particle emitting mesh.

Particle Instance Modifier Panel - With the PSYS: field highlighted in yellow.

As an example, below is a single plane mesh with 2 areas (the first area shown in Red and the Second in White) with different Particle Systems applied to each area. The left side using a Particle Instance Modifier which has the shape of a sphere and the right side having a Particle Instance Modifier which has the shape of a cube.

Render showing a single Plain mesh object assigned to 2 different vertex groups and each of those vertex groups is assigned a separate and independent Particle System, with each Particle System being assigned a different Particle Instance Modifier. In the case shown the Particle Instance Modifiers are a sphere and a cube.

The Blend file for the example Render above can be obtained here:

Media:Manual - Modifiers - Particle Instance Modifiers - Split Plane.blend

• Normal:

The Normal button (highlighted in yellow) when selected tells the Particle Instance Modifier to draw instances of itself wherever Normal Particle types are emitted from the underlying Particle System, obviously the Particle Instance Modifier has to have been told to have an influence on the underlying particle emitting system (by entering the name of the object to influence in the Particle Instance Modifiers Ob: field). So if the current Particle Instance Modifier is a sphere shape, when Normal particles are emitted a sphere will now appear as well.

Particle Instance Modifier Panel - With the Normal button highlighted in yellow.

• Children:

The Children button (highlighted in yellow) when selected tells the Particle Instance Modifier to draw instances of itself wherever Children/Child Particle types are emitted/used on an underlying Particle System, obviously the Particle Instance Modifier has to have been told to have an influence on the underlying particle emitting system (by entering the name of the object to influence in the Particle Instance Modifiers Ob: field). So if the current Particle Instance Modifier is a sphere shape, when Children/Child particles are emitted a sphere will now appear as well.

Particle Instance Modifier Panel - With the Children button highlighted in yellow.

• Path:

The Path button tries to make the mesh object that has a Particle Instance Modifier associated with it, deform its mesh shape in such a way as to try and match the path travelled by the particle/hair strands associated with the mesh object.

Particle Instance Modifier Panel - With the Path button highlighted in yellow.

For example, shown below is a screen shot showing the path of a single Keyed Particle as it travels its way through each of the different way points 1 through 4 (Target Particle Systems), when it reaches way point 4 the particle dies and ends its journey.

Keyed Particle Following way points showing 1 particle.

The Blend file for the example Render above can be obtained here:

When a Particle Instance Modifier is added to a cylinder object and then associated with the way point 1 particle system, the particle position is copied by the cylinder and placed at the particles position. So the mesh object follows the location of the particle. The cylinder does not alter any of its other properties when following the particle, only the cylinders location gets altered, shape and rotation do not get altered. See screenshot below:

Keyed Particle Following way points showing a mesh object (Particle Instance Modifier) in place of the original particle.

The Blend file for the example Render above can be obtained here:

Both of the above examples had the Particle Instance Modifier Path button deactivated.

When the Path button is activated the effect can be seen in the screenshot below:

Keyed Particle Following way points showing a mesh object (Particle Instance Modifier) in place of the original particle, that is also being deformed to fit the travel path of the original particle.

The Blend file for the example Render above can be obtained here:

Instead of the cylinder location just following the position of the particle (and not altering its shape), the cylinder tries to fit its mesh to the shape of the path followed by the particle.

The mesh geometry of the object which is trying to deform can have an impact on how well the deformation is carried out. In the case of the cylinder, it has many loop cuts along its length so that it can bend at those points to deform along the particle path.

For example here is the same scene with the number of loop cuts along the length of the cylinder reduced, showing the effect on the deformation of the cylinder along the particle path.

The Cylinder has most of its edge loops so most of the Path deform is very regular apart from at the very end of the curve.	The Cylinder has some of its edge loops removed so the Path of the deform starts to become less regular.
Now the deform Path is very rough.	At this point there arn't any vertices to bend the Cylinder to follow the Path and instead the Cylinder just goes directly to the last Way Point 4.

Once all the extra edge loops around cylinder are removed so that there is only the top and bottom vertices left, meaning that the cylinder doesn't have enough geometry to bend, in that case it cannot follow the path of the particle, so it just goes from the start Way Point 1 to the ending Way Point 4.

The Particle Instance Modifier Path button control as well as working for Keyed Particles also work for Hair (strand) Particles. In this case the mesh of the Particle Instance Modifier will follow the length and profile of the hair strands paths.

Below is a screenshot showing the effect of the Path button on hair.

Strand with a Particle Instance Modifier associated with it and deforming the Cylinder along the hair profile.

The Blend file for the example Render above can be obtained here:

Strands when they are generated instantly die when created so for the Path button to be of any use, you must also have the Dead button selected so that dead strands are displayed, otherwise the path a mesh took will not be visible.

• Unborn:

The Unborn button (highlighted in yellow) when selected tells the Particle Instance Modifier to draw instances of itself wherever Unborn Particle types will be emitted/used on an underlying Particle System, obviously the Particle Instance Modifier has to have been told to have an influence on the underlying particle emitting system (by entering the name of the object to influence in the Particle Instance Modifiers Ob: field). So if the current Particle Instance Modifier is a sphere shape, when Unborn particles are present a sphere will now appear as well.

Particle Instance Modifier Panel - With the Unborn button highlighted in yellow.

• Alive:

The Alive button (highlighted in yellow) when selected tells the Particle Instance Modifier to draw instances of itself wherever Alive Particle types will be emitted/used on an underlying Particle System, obviously the Particle Instance Modifier has to have been told to have an influence on the underlying particle emitting system (by entering the name of the object to influence in the Particle Instance Modifiers Ob: field). So if the current Particle Instance Modifier is a sphere shape, when Alive particles are present a sphere will now appear as well.

Particle Instance Modifier Panel - With the Alive button highlighted in yellow.

• Dead:

The Dead button (highlighted in yellow) when selected tells the Particle Instance Modifier to draw instances of itself wherever Dead Particle types will occur on an underlying Particle System, obviously the Particle Instance Modifier has to have been told to have an influence on the underlying particle emitting system (by entering the name of the object to influence in the Particle Instance Modifiers Ob: field). So if the current Particle Instance Modifier is a sphere shape, when Dead particles are present a sphere will now appear as well.

Particle Instance Modifier Panel - With the Dead button highlighted in yellow.

[edit] Examples

Examples of Usage and Tutorials here.

[edit] See Also

Related topics here.

Manual