Control Point (particles)
From Valve Developer Community
In particles, a Control Point is a Vector variable that enables external values, like locations or colours, to be passed into a particle system.
Each system can have up to 64 CPs, but the first, 0, is reserved as the system's origin. 
Confirm: Children inherit the CPs of their parent.
Specifying
- In the particle system
- Use one of the following operators:
- To temporarily set a value, use the "Ctrl Pts" tab of the preview window.
- In a map
- Fill in the fields of the info_particle_system used to spawn the system.
- In code
- See Particles In Code#Control points.
- In a QC file
- Confirm: It is not possible to configure control points when compiling a model. However, see the Position on Model Random initializer.
Using
There are many particle functions which can be configured to read values from a control point. Of particular interest are:
- Operators
- Remap Control Point to Scalar
- Remap Distance to Control Point to Scalar
- Remap Distance Between Two Control Points to Scalar
- Initializers
- Remap Control Point to Vector
Note:There is no 'CP to Vector' operator, just this initializer. The reasons for this omission are not clear. - Remap Control Point to Scalar
- Remap Initial Distance to Control Point to Scalar
Using these functions, a CP's value(s) can control the following particle values:
- Scalar
- Lifespan
- Creation time To do: Same idea as pre-ageing, or affecting spawn time?
- Radius
- Roll speed
- Alpha
- Alpha alternate To do
- Sequence number
- Sequence number 1 To do
- Trail length
- Particle ID
- Yaw
- Vector
- Position
- Roll
- RGB Colour (normalised)
