This scene contains two chain links, one vertical link (VertLink_01) and another horizontal link (HorzLink_01). This is a simple explanation on how to build and use concave shapes with Box#2.
Each link is built with 16 cylinder primitives each with a bend modifier set to 22.5 degrees ( 360 / 16 = 22.5 ). The cylinders are then grouped. These have been converted to an editable mesh (you can use editable poly, or simply group the cylinders) and attach the remaining 15 cylinders. These links are simple loops, you can create nearly any shape you like as long as you use the Birth Group Operator to birth the particle shapes. This is the only Birth Operator that gives you the option to separate particles by group, element, or parent.
NOTE: The HorzLink01 has a reset XForm applied, this is because it is a clone of VertLink01. Its World Space coordinates should be reset for Particle Flow to give an accurate creation of the Birth Group shapes.
The next step is to clone the links to the desired length. We will use the array tool.
Select the scene objects VertLink_01 and HorzLink_01
Menu >Tools > Array Tool
Type of Object - Instance
Array Dimensions - 1D - Select the amount of Link instances you wish to make, we will use the default of 10.
Enable Preview
Incremental - Move - X-axis - 48.25
Click OK
Delete the last horizontal link (HorzLink_10)
In the front viewport create a Cylinder
Keyboard entry:
X - 0.0
Y - 0.0
Z - negative 75.0 (-75.0)
Radius - 5.0
Height - 150.0
Add a Pflow Collision Shape Modify and activate
In the Top Viewport, shift+drag clone the Cylinder01 object and move along the X-axis to 435.0
Part 2 - Building the Flow with Box#2
Our scene geometry is now complete.
Open Particle View (Keyboard Shortcut 6) to create a new particle flow system.
Drag a new PhysX Flow into the field
Remove the Shape operator
Remove the Spin operator
Create or drag a new Birth Group operator into Event01
Set the PhysX Shape operator to Type - Convex Hull
Shift + Drag Event01 to clone a copy - choose copy
Select Event01 Birth Group
Click By List
Select all of the "LinksHorz" geometry and click OK
Select Event02 Birth Group
Click By List
Select all of the "LinksVert" geometry and click OK
Add or append a new PhysX Collision test operator
Select both cylinders
Click the PhysX World operator
Press the "=>" -Access Driver Parameters- button
In the modify panel notice the PhysX World Driver is now selected, scroll down to advanced parameters, open the rollout
Set the Sub-frame Factor to 10 -- to increase system accuracy, this is just a starting point
NOTE: a good rule of thumb for this setting, "Max Binds p/Particle" multiplied by 2 plus 2 or (MBP*2)+2
Rename the events to Horizontal Links and Vertical links
Next to confirm that we have setup the link shapes correctly do the following steps:
Select the PhysX Shape Operator
Set the 'Display As' to Shaded --the particle shapes should turn yellow and match the particles shape, if not the base shape object or the Birth Group have not been setup correctly
Go to the Birth Group
Uncheck Object Elements
Click Update Particle Shapes From Objects --If you setup correctly the links should now appear as a disk shape instead of a torus
Check Object Object Elements
Click Update Particle Shapes From Objects --to return back to the particle back to their original state
Next add a Glue to both Events
Add a PhysX Glue Test operator
below the PhysX World -- to create binding, this will retain the links shape
Set the type to Rigid
Bind Distance - 12.0
Max Binds p/Particle - 4
Enable Visualize binding
Right-click the Glue Test and click copy
Right-click below the PhysX World operator in Event 02 (or the Vertical Links event if you renamed them) and click paste, choose copy
Select the Perspective Viewport and hit F3 to go into wireframe mode, you should now see your glue bindings
Play the animation
Notice the amount of bounce. This can be reduced with a PhysX Drag operator. This will behave much like a standard drag spacewarp by inducing drag on the particle surface slowing them down.
Add a PhysX Drag operator above the PhysX World
Enable Linear and set to 3.0
Set the Angular to 0.5
Right-click the PhysX Drag operator and click copy
Paste an Instance in Event 02 --The Instance clone will ensure that if you change either one of the PhysX Drag operators parameters that it is duplicated to the other operator, maintaining consistency.
Play the animation
The bounce has diminished significantly
Part 3 - Skinning the Links
We will use the Particle Skinner Modifier to skin the particle bones we just created.
Unhide Torus 01 and Torus02 from the Particle Skinner Layer in the Layer Manager.
