Essential Blender- P23 ppsx

A particle system is created by RMB selecting a mesh object, and clicking the "New" button in the Particles panel of the Object buttons F7, found in the Physics buttons subcontext... In

Figure LT.29: amb occ render with default settings A render lit only with Ambient Occlusion

Raising the Samples value for Ambient Occlusion smoothes out the graininess, but, of course, takes longer It's quite common to work on a scene that will include Ambient Occlusion with a very low sample value, like 2, to enhance speed for[KM] while you get things as you want

themtweak the rest of the scene After that, you can turn it up to 10 or so for your final render and get yourself a cup of coffee

To demonstrate how believability in an image can be significantly enhanced by using Ambient Occlusion (often usually referred to as "AO"), let's bring back our Area lamp Enable Layer 3 (by Shift-LMB on the Layer 3 button on the 3D header, or by using Shift-3), and render) Since the

AO is already adding a significant amount of light to the scene, turn the Area lamp's Energy slider even further down to 0.1 Render

The result is a softly lit scene with a high degree of believability If you would like to really remove the grain in the render, change the AO samples to 10 and check the new result AO samples can be set as high as 16, but excellent results are usually achievable without going that far

Figure LT.30: final render The final render

Conclusion

Lighting is an art form in itself Large CG companies have artists on staff who do nothing but lighting It is a complex topic , one that can make or break a scene While we've shown you the mechanics of using Blender's lighting tools in this tutorial, we encourage you to work through the discussion section of this chapter, and to seek out other resources to enhance your artistic

abilities

Chapter 12: Particle Toolset Discussion

By Roland Hess

Particle systems are different from other Blender objects in a number of ways First, instead of being made of faces, edges and vertices, they are composed of a large number of points (up to 100,000) Second, the locations of these points are calculated by Blender and are based on velocity and force values, instead of being modeled by the user into exact shapes

Figure pd.01: Various particle systems, both rendered and in the GUI

Particle systems can be used for a variety of effects, but are most commonly found when making

"aerial" effects like smoke, fire, clouds, dust motes floating in sunlight, magical sparkles

swarming around an actor you get the idea

Emitters

Particle systems need a place to start That place is an "emitter."

In Blender, an emitter can be any mesh object you choose The shape of the mesh will form the starting point for the particles

A particle system is created by RMB selecting a mesh object, and clicking the "New" button in the Particles panel of the Object buttons (F7), found in the Physics buttons subcontext

Tip:

Particles systems are generated by emitter objects

Figure pd.02: The Particles panel In the default configuration, the Particle Motion panel is nested

as a tab behind the main Particles panel, but we've pulled it out to show you everything at once

Before you examine the particle tools, a couple of points about particle systems in general are in order:

- There are two kinds of particle systems, Static and Dynamic, each of which has its own tutorial Static particles are used for systems of Strands like hair, fur and grass Dynamic particles are used for the previously mentioned fire, smoke and dust effects - Unless you take special steps, the emitter mesh itself will not show up in a render

The most basic settings for particles are found in the "Emit" section of the panel

Amount: This is the total amount of particles in the system How many you use will vary in relation to exactly what you are trying to do Keep in mind that more particles will take more calculation time, and, depending on the speed of your computer, may slow things down

significantly

Sta: This stands for start, and refers to the frame number on which the emitter will begin to create particles

End: The last frame on which the emitter will create particles

An emitter will create particles at a constant rate between the Start and End frames So, with only these three controls, you can cause some serious differences in the way particle systems can act 10,000 particles being created between frames 1 and 1,000 will make 10 particles per frame, a fairly low rate On the other hand, 10,000 particles with a Start of 1 and an End of 2 will cause a burst of all 10,000 particles within 1 frame Think of a fireworks explosion

Life: How long each particle will live Particles hang around in the scene for only as long as this parameter will let them After they die, new particles will be emitted to take their place, up until the End frame is reached

A low Life value (a couple of frames) will have particles blipping into and out of existence rapidly, like short-lived sparks thrown from a welding torch Life settings that are longer than the amount of time the particles are actually being emitted will cause a build-up effect, with all emitted particles hanging around in the scene long after the End frame

Disp: Percentage of particles to display This is indispensable when you are working with particle systems that have enough particles to slow down your Blender experience The value here is a simple percentage: 10 shows only 10% of the total particles, 50 shows 50%, etc The really nice thing is that it is not just a display speedup Until render time, Blender does all of its particle calculations on this reduced amount, giving good speed boosts for any particle-related activities When you render your scene, though, the full particle amount is used

You can also control which parts of the mesh emitter the particles come from, in the

appropriately named "From:" section of the panel

By default, both the "Verts" and "Faces" buttons are On, meaning that particles can be emitted from either vertices or faces For certain effects, you could restrict it to one or the other by setting either to Off For example, if you wanted to create an effect where particles emitted in a burst from several points on a grid, you would turn off the Face option

Figure pd.03: The particle system on the right shows particles emitting from faces and vertices The one on the left only emits from the vertices

Rand: Creates a truly Random distribution The normal distribution of particles looks pretty random to the untrained eye, but from a mathematical perspective it isn't Without getting all math-geeky, really random things tend to cluster and clump Their elements are not as orderly as the standard particle layout When looking at the illustration, you can see patterns in the standard emit, but none in the Random emit

Figure pd.04: The particle system on the left has the normal particle distribution The one on the right is using the Rand option

Even: Attempts to distribute particles evenly over the surface of the mesh emitter Usually, Blender assigns particles on a per-face basis, meaning that in a 20,000 particle system, each face

of a 100 face mesh gets to emit 200 particles That sounds fine until you realize that some areas

of the emitter mesh might have more densely packed, smaller faces Particles will be denser in those areas

Using the Even option attempts to alleviate this by assigning each face a number of particles in proportion to its part of the area of the mesh You need to be careful when using this option with things that could change the shape of the mesh though: shape keys, character animation through armatures, lattices, etc These tools can change the relative sizes of faces in your mesh, causing particles to seem to jump around as they are reapportioned for different face areas

Vgroup: Vertex Group Vertex groups are covered in Chapter 4 You can enter the name of an already-created vertex group here to cause only that portion of the mesh to act as an emitter

Figure pd.05: A mesh with a vertex group of a face saved The particles are set to emit from the

"face" vertex group

Materials: What do the particles look like?

Particles use a material option that is not covered in the Materials and Texturing chapter We'll go over it here To get the most out of this, you should probably have read Chapter 9 so you

understand the basics of creating and working with materials and textures

By default, particles are rendered with the Halo material Halos are rendered at a different stage than normal geometry, and are strictly 2D effects placed into the final render

Note: Halos do not react to raytracing, so they will not show up in Ray reflections or Ray

transparency Also, as they are a 2D post-render effect, Halos cannot cast shadows

The following illustration shows what halos can look like:

Figure PD.24,25,26: A particle system, showing two different Halo settings

A material's halo options can be accessed by enabling the "Halo" button on the material's Links and Pipeline panel

Figure PD.22: The Halo options for materials

Tuning Halos to get them to do what you want is not an exact science A lot of trial and error will

be involved, so try not to become frustrated

HaloSize: This controls the overall size of the Halo When working with Halos, this is the first setting to start playing with

Hard: This control varies Halos from rendering as tiny dots with a small lightness surrounding them (1.0) to diffuse circular blobs with no discernible center (0.0) Particles that should look like

"magic" would have high Hard values, where smokes and other less defined effects would require near-zero values

Add: Determines the level to which Halo effects reinforce themselves Normally, several halos stacked in front of each other would only render the values for the nearest halo With Add turned

up to 1.0, stacked Halos reinforce each other, accumulating their brightness Particle systems that are meant to simulate fire should have high Add values

In addition to the "glowing ball" look, Halos can be given other properties, too

Figure PD.23: Ring, Lines, Star, and all three together as Halos

The particle systems in the illustration show the effects of the Ring, Lines and Star buttons on the Shaders tab The buttons can be combined, as seen in the system on the lower right The numbers

of Lines and Rings are controlled by the corresponding spinners on the same panel Line and Ring color can be adjusted individually through the color pickers on the Material panel, where the Spec and Mirror colors normally reside

Shading

By enabling the "Shaded" button on the Shaders panel, you can make Halos react to light

Figure PD.27, 28: The same particle system, rendered as both Shaded Halos and non-Shaded

Any particle effect that would be shaded in real life, like smoke or clouds, should use this setting

"Magic" effects, or anything that appears to glow, like fire, should avoid the Shaded option Alpha

In most cases, good particle effects will require reducing Alpha and enabling ZTransp For example, when making a cloud effect, you could simply make a low number of particles (100 or so) and give them a large HaloSize and high Alpha value (0.9) This would produce a cloud, but

it would have very low detail A better way to go about it would be to increase the number of particles (say, to 5,000), drop the HaloSize and drop Alpha to around 0.1 This would produce a cloud of the same overall density, as the drop in Alpha would offset the larger number of

particles, but with much better detail and more of a sense of volume

Display

The set of buttons that is labeled "Display" contains controls that determine how particles appear both in the 3D view and at render time

Material: the Material spinner selects which material index of the emitter you want the particles

to use In Blender, meshes can have several materials attached to them You will need to refer to the emitter's Material buttons panels to see which number corresponds to the material you would like to use If you are not enabling the Show Mesh option, though, there will almost certainly only be a single material linked to your emitter

Figure pd.06: The Material panel, showing material index numbers

Mesh, Unborn, Died: These buttons control whether or not the mesh, unborn, or dead particles show up in the final render If you want particles to show up before they are emitted (unborn) or after they have reached the limit of their Life setting (died), you can do so with these buttons For example, you may want your particles to represent "fairy lights" or some such thing, which begin their life speckling the outside of a tree As the animation progresses, they fly off and about In this situation, you would enable the "Unborn" option so that particles that have yet to leave the tree are still visible

Under normal circumstances a particle's mesh emitter will not show up in a render The Mesh button makes it visible

Vect: Causes particles to render as lines instead of points, with the line facing along the direction the particle is moving The "Size" spinner beside this button controls the render size of the

vectors, not their lengths

Figure pd.07: Difference between standard particles, and vector particles

Children

If you want your particles to generate new particles when they die, you use the Children tools

Figure pd.08: Particles with children

In the interface presented here, the Generation: 0 in the spinner is the first, main emission of particles To make particles create children when they die, adjust the "Prob:" spinner, which refers to the probability that a particle will emit a child when its life ends At the default setting,

0, no particles will emit children If you choose 1.0, this corresponds to a 100% chance that a particle's death will result in a child, meaning that all particles will spawn children when they die

To add additional generations of particles, use the Generation spinner to move into generations 1,

2 and 3 and adjust their probabilities to something other than 0

Currently, child particles use the same motion settings as their parents, so children are limited to doing simple fireworks effect

Particle Motion

Once you have decided how many particles to emit, how long they live, and how they will be visualized, you have to define how they will move

Motion is controlled on the Particle Motion panel that shares tabs with the main Particles panel

Figure pd.09: The Particle Motion tab

Velocity Controls

Normal: This spinner gives particles a velocity based on the surface or vertex normal of the emitter at the point where the particle is created The non-technical explanation is that this will cause particles to shoot straight out from the surface emitter This control can give very fast motion, so you might want to begin by clicking on the spinner's right arrow section which will advance the value by small increments

Object: When emitted, particles have the same direction and velocity as their emitting object at that point in the timeline If your object is not animated and moving, this setting will have no effect However, if your emitter object is moving and spinning in 3D space, you get nice

animated particles With values approaching 1, all of the emitter's motion is used, and the

particles will appear to fly off of it as though under the object's momentum Lower values, for example 0.2, will have the particles string out behind the emitter, but with a small amount of following motion, like a smoke trail

Random: This control adds a bit of random motion on top of that generated by the other controls Usually, very low values (0.001-0.025) will add believability to certain effects However, this control can easily override and essentially destroy other carefully refined control values,

especially if it is cranked the whole way up to 1.0 Try it and see

Damping: Damping is a sort of friction control 0.0 damping means that particles will continue at their initial velocity until the end of their lives: they will not slow down Turn damping up to 1, however, and the particles will quickly slow to a stop, almost immediately after they are emitted

Force controls

The force controls are simple There are three spinners, one each for the X, Y and Z axes The spinners can range from -1.0 to +1.0, and apply a constant force along the indicated axis

As an example, let's pretend that you would like your particles to appear to be affected by

gravity The Z axis represents up and down, so to fake the effects of gravity, you could try a value of -0.5 in the Z force spinner This applies a constant downward (negative Z) force on all particles -0.5 may or may not be the right value to enter, but simply playing the animation in the 3D view will give you good feedback on whether it looks correct or not

On the opposite end, you could add a small positive value to the Z spinner in order to simulate the way that smoke climbs into the air after it is emitted

Texture Motion and Other Controls

There are a number of other controls for particle motion, many of them concerned with textures and groups Using 3D textures to control and alter the motion of particles can be tricky, and is a topic that, if covered thoroughly, would double the size of this chapter That being the case, it will not be covered in this book

Force Fields

Particle motion can also be affected by Force Field objects These are usually Empty objects that have been activated in the "Fields and Deflection" panel of the Physics buttons