Velocity in the context of real-time VFX, like those created in Niagara (Unreal Engine's VFX system), refers to the speed and direction at which a particle is moving.

Think of velocity as the "motion" of a particle.

• Speed tells us how fast the particle moves.

• Direction tells us where the particle is heading (e.g., up, down, sideways)

How is Velocity Used in Niagara?

1. Making Particles Move

   • If a particle has no velocity, it stays still.

   • Adding velocity makes it move. For example, applying upward velocity will make particles rise like smoke.

2. Controlling Movement

   • You can add velocity in specific directions (e.g., X, Y, Z axes).

     • Positive Z → moves particles upward.

     • Negative Z → moves them downward.

     • Positive X/Y → moves them sideways.

3. Simulating Realistic Effects

   • Fire, explosions, rain, and sparks all use velocity to look natural. For example:

     • Sparks in an explosion move outward rapidly with high velocity.

     • Raindrops fall downward with a constant velocity.

4. Forces and Velocity

   • Forces like gravity or wind can change a particle's velocity over time.

     • Gravity adds downward velocity to make particles fall.

     • Wind applies velocity in a sideways direction.

5. Velocity Fields

   • In Niagara, you can use velocity fields to create complex movement. For example:

     • Smoke swirling in circles.

     • Debris being pushed away from an explosion.

Practical Example in Niagara

• Fire Effect:

  • Add upward velocity to particles → flames rise.

  • Add randomness → flames flicker and move naturally.

  • Apply gravity → as fire fades, particles slow and drift down like ash.

• Explosion:

  • Give particles high initial velocity in all directions → particles burst outward.

  • Gradually slow them down using drag or friction → particles settle naturally.

Velocity in Real-Time VFX

Written with the help of ChatGPT*