VFX Particle 101 Emitter Type Physics

There is one major topic of Blender I would like to cover since I began blogging at Blender Sushi, which is PARTICLE.

Not until today, when I finally fully confident with my understanding of Blender Particle System. Of course, I still look into other documentation time to time, but most important in understanding Particles is actually knowing where to look for answers.

Particles is such a huge area that often got a person confused or stucked. More likely it is the case that the foundation or the basic was not understood well.

Most book dealing with Particles will just quickly talk through the really basic setup and then show some super complex examples. There is a huge gap there, actually.

I like to teach the "core" idea of Particles, the way I have understood Particles until today from many different perspective. Hopefully I can sort of explain each elements of Particles clearly, so that you can start connecting the block together.

Beginner artists tend to fall into trap wanting to do super complex effects, without knowing the basic elements and also the limitations of certain particular system. Good artists know the strength of particular system and find a way to tackle dynamic problem in multiple ways.

ZEN OF PARTICLES: Shortcut vs No Shortcut
If you browse through Internet, you will find hundreds tutorials on how to create Fire, Snow, Tornado, etc. Those step-by-step tutorials are fine, do read and try them. They will teach you single solution for single problem. Some tutorials are better than others, just because those better tutorials will try to teach you a bit more than just single solution. There are multiple ways for a single problem.

Maybe we can think of it like a Martial Art Stance. You dont learn COMBO at first. You want to learn how to do high kick, low kick, high punch, low punch, block, twist, turn, to create YOUR OWN COMBO.

Blender actually kind enough to provide you example of SHORTCUT. If you hit SPACE on your scene and type "Quick" ... and you get 4 options to create:

• Quick Fluid
• Quick Smoke
• Quick Explode
• Quick Fur

Those are the quickest way to create 4 kinds of complex Particles out of the box.

Only until if you know how to create those 4 quick Particles manually and tweak it to your needs, then you have mastered the foundation of Particles.

So, as you can see Particles is part of computer graphics that very quickly branches to many different areas of VFX. I will try to write many posts just about Particles from today. If you understand the core foundation of particles, you can go really far.

PARTICLES: BLENDER VS MAYA VS HOUDINI
How does Blender Particle compared to other commercial 3D packages? Based from my experience using 2 other packages: Maya and Houdini, I can say that Blender current Particle system is pretty robust and powerful, enough to cover most artists particle needs. In term of practicality, Blender Particle is also very intuitive, once you understand how things work. It renders beautifully (and fast) and quite efficient.

Is Blender Particles system hard to master? Actually no. Maya and Houdini Particle is REALLY hard to master. Blender Particle is EASY. "Limitation" of Blender Particle makes it easier to digest.

Blender Particles also extends its functionality into many other area, such as: Hair/Fur Simulation, Fluid Simulation and Smoke Simulation. Some commercial 3D packages make it really complicated for user to get from zero to final result.

PAST, PRESENT AND FUTURE
From the development rumour, Blender will have an exciting brand new Particle system that is fully node-based. It is going to be awesome, in the meantime, we will use the current Blender Particle.

Current Blender Particle system is actually a system that has been slightly reduced in functionality when Blender interface got upgraded from 2.49 to 2.5x. Now in version 2.6x, Blender has a much better UI (people should get used to it) and pretty limited Particle system (no reactor, particle cannot trigger or born another particle via event), but plus the awesome additional Dynamic Paint. Not to worry, even with this  limitation, Blender Particle is still pretty powerful and can do lots of cool effects.

WHAT MATTERS
When talking about Particles, we basically must care about two main things: THE SIMULATION and THE PROPERTY/THE LOOK of Particles. And while doing so, we also care about EFFICIENCY and COST. No point in creating particle effects that cannot be rendered (crash) or look ugly in the end. We do not want that to happen.

WHAT IS PARTICLES IN CG?
A single particle in computer graphics representing a single dot in 3D space. A single particle may not be very interesting, but a bunch of particle (millions or more) and you can create some amazing effects: dust, crowds, boids, debris, sparks, tornado, snow, rain, blood cells, etc: And also all not so obvious particle effects: hair, bullets, stars, fireflies, arrows, candies, and so on.

EMITTER MATTERS
Every Particle is born from a source we called an emitter. In Blender, only polygon mesh object can emit Particle, Curve object, Text object, cannot emit Particles unless you convert them to Mesh first (Alt+C).

Polygon mesh in Blender can emit Particles in a form of this mesh:
1. VERTEX: A single tiny vertex point / point cloud.

2. Edge(s) --- OK,  I lied, Blender cannot really emit from edge, but you can sort of trick the eyes.

3. FACE: A single face / multiple faces

Single face or multiple faces of geometry can emit particles.

4. VOLUME: Volume boundary of 3D geometry

Only mesh with actual "volume" can emit particles in volume.

CREATING YOUR FIRST PARTICLE

1. Have a polygon mesh of some sort. Select it (right click).
2. Go to Particle Tab under Properties pane.
3. Hit (+) to add a particle system. This will add Particle system that is linked to your mesh.

EMIT LIKE A BOSS!
When you created Particles by default it will probably confused you a bit. It actually does few things, I will give you some rundown:

• EMISSION: Create Emitter type of Particle
• EMISSION:  Start at frame 1and end at frame 200
• EMISSION:  Lifetime of 50.000 (50 frames)
• EMISSION:  Random lifetime of 0.000
• EMISSION:  Emit from Faces (randomly, evenly, jittered)
• VELOCITY: It has NORMAL velocity of 1.000 (!)
• ROTATION: It has Angular Velocity set to Spin (!)
• ROTATION: It has Rotation Axis set to Velocity/Hair (!)
• PHYSICS: It has Physic set to Newtonian (!) with all its default settings.
• RENDER: It has Emitter set to render (your emitter mesh will be rendered) (!)
• RENDER: It will have attribution from Material: 1 (based on geometry)
• RENDER: Particles will be rendered as Halo (!) This is the reason why when you create Particle and render it, it will look like Halo. You must adjust the Halo so it looks like a dot.
• FIELD WEIGHTS: It is affected by World Gravity by default (!)

This is ALL internal settings and parameters available of Particles Simulation

All the above I marked with (!) will need to be zeroed or tweaked, if you want Particles to behave itself (stay still) and rendered as single dot(s) with no other fancy stuffs. I always tend to do this:

1. Set NORMAL velocity to 0. This means Particle will stay at the spot where they are born and will not get pushed by the "normal".

2. Set local GRAVITY influence to 0.

Once you do that, your Particles will stay on the spot where they got born and disappear (die). From here, it is up to you how you want to control them:

If you do need gravity, turn the gravity back on to value of 1. The actual force of gravity (-9.8) is as below:

Remember that you dont always need gravity for particles.

If you do need particle to be pushed by the emitter normal, then add some value to the normal. Normal tends to be boring, because the force of normal moves Particles in straight and linear fashion. If you want Particle to move irregularly and with more excitement then you want the particle to be pushed by FORCE FIELD. Add the force to the scene:

Shift+A and then select Force Field you want to create.

Give each force a try for now. Delete them if you dont want.

SEED OF PARTICLES
You may notice Seed:0 just under Particle System panel. Seed is basically a variation of particles. Particle with same seed number will be born "identical". You want to give different seed value if you have same particle setup but would like different results.

One Emitter can have multiple Particles System, on the other hand a single Domain can contain multiple Flow of particles. Just keep this in mind, useful when you get to Smoke and Fluid simulation.


PARTICLE TYPE
1. Emitter
Particle type set to Emitter just means it will born as regular particle, as a point or a dot in 3D space.

2. Hair
Particle in Blender has direct connection to Hair. Hair in Blender is originated from Particles, but it has its own additional special dynamic physics that allow it to behave like hair. Particle as Hair will also allow Blender to render it as Strands of Hair realistically.

3. Instances based on Emitter
Instances is how Particles can represent other 3D geometry. If you have a ball, you can instance it into millions ball using Particles and it is much more efficient than duplicating the ball millions times. It will carry some of Particles attributes, such as: location, size. There is unfortunately a limitation of current Blender Particle system is that Particle will NOT transfer the color into the instance. But there is a way around it, we will get into it at later stage.

PARTICLE PHYSICS
This controls how the particle will be simulated when playback is running.

• No: This means no physics on the particle, switching off every Particles attributes, leaving you just Instances or duplication ability. Sometimes you want this. Ocassionally, you would set it to Newtonian, while switching off most of forces, just so that you still have some attribution that can be passed into others. Smoke for example, requires you to have Newtonian and a bit of Normal force for it to emit.
• Newtonian: The most typically used Particle physics, just like how it behaves in our world.
• Keyed: You can keyframe particles from one system postition to next system position.
• Boids: Particle with own mind, not very clever, but can travel following the leader.
• Fluids: Not a real fluid simulation, but useful in some cases
• Hair: If you turn on Hair system, you can then have Hair dynamics.

For beginner and most of cases, you can just use Newtonian, but you can of course try other physics too and do your own observation for each physic sunykatuib. But dont go too far because you have not yet touch all the elements.

TO BE CONTINUED...
Ok, seems like this 101 article is getting too long and very wordy. I actually want to do video tutorials to accompany this 101, hopefully I have time and energy to do so.

I will continue discussing about Particles, in Particle 201, in which I will be talking about Particles Lifetimes, Color, Size, Velocity. Mostly about THE PROPERTY/THE LOOK of Particles.

More extra tricks coming along the way!

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