Environment particles is a way of adding a uniform volume of particles that cover an entire world in the engine. It is useful for things like rain, snow and water particles. They way it works is the engine keeps track of a single volume that is then tiled across the entire map. Think of this volume just like a texture that tiles across a large 2D plane. When each particle is reaches the edge of the tiled volume, it wraps a around, thus forming a seamless pattern of particles across the world. When rendered the engine only renders a volume-sized (in our texture analogy, the size a single texture takes up on the plane) at a certain distance from the player.
This volume is a chunk of the entire tiled volume so as the camera moves around in the environment. This chunk can then be rendered several times, each time with a randomized offset to positions and rotations, in order to create a dense collection of particles. All this is done on the GPU and is really fast. There is no problem with having the basic volume filled with 1000 particles, and then have 10 iterations, giving a total of 10k particles. The main bottle neck is probably overdraw, so the feature is best suited for smaller particles that do not cover much of the screen (and seldom cover each other).
ParticleNum
The number of particles in side the volume.
BoxSize
The sized of the tiled volume containing the particles.
SubDivUV
The number of sub textures inside the texture for the particles. 2×2 means a that 4 sub textures are randomized between all particles.
ParticleSize
The size of the particles. Remember not to make them too large if many are required.
AffectedByLight
If the particles should be affected by light in the scene. The way this works is that 3 light probes (one close to the camera, 2 further away) gather light-amount from lights that intersect with them. These three values are then interpolated between for each light. It is not perfect, but does a decent job.
BoxDistance
The distance from the player at which the volume is rendered.
FadeInStart, FadeInEnd, FadeOutStart, FadeOutEnd
Parameters for how the particles in the rendered volume fade in out. All distant are measured as z-distance from camera.
IterationNum
The number of particles that If it has a fraction (eg 13.45), the fractional part (eg 0.45) determines the alpha of the last iteration. (to allows fading iterations)
Color
The color the particles are modulated by.
GravityVelocity, WindVelocity
Two different velocity values for each of the particles.
RotateVelocity
The speed at which the particles rotate around the center of the volume.
GravitySpeedRandomAmount, WindSpeedRandomAmount, WindDirectionRandomAmount,RotateSpeedRandomAmount
The random variations are added to any iterations after the first! Valid values for all amounts are 0 - 1 (can be others, but not recommended).
What it does it that any subsequent iterations will have the vector updated like: vector + vector*random amount. So if the vector is (0,1,0.1) and if the random amount is 0.1, then any subsequent iterations will have values between (0, 0.9, 0.09) - (0, 1.1, 0.11). Wind direction random is a bit different, what is does is that it rotates the vector (around all axes) by around amount. Wind random amount of 1 means, it can rotate into any direction of a sphere, 0.5 means half a sphere, 0.25, quarter of a sphere and so on.
Also note that the random values are psuedo-random, this means that they do not change depending on play through, but they are always they same. So if it looks like something in the editor, the random distribution will look exactly the same when you view it later in the game.
RotateSpeedRandomBothDirs
If the rotations can go the opposite direction too.
Lens flares are a bright spot that appear at the center of a strong light source.
Lens flares are created by light entering through a camera objective and reflecting multiple times off the surface of the numerous lenses inside it, creating several recognizable artifacts.
The Adobe Flash Plugin is needed to display this content.
lens_flares.png
Each lens flare consists of a few different kind of flare types that can be active at the same time.
Flare
A normal flare that rotates slightly depending on its position on the screen.
Anamorphic flare
A flare that stretches in either horizontal or vertical direction. The anamorphic flare stretches out more the closer it gets to the edge of the screen.
Multi Iris
A line of small iris shaped artifacts stretching toward and away from center of the screen. The brightness/size/sub-texture of each individual iris is randomly determined by the seed of the flare.
Material
The material of the flare type. Additive blend and depth test disabled are recommended for best result.
Color
Size
The size of the flare type. A value of 1.0 means that it covers the whole screen.
Outer Field of View
The angle in degrees of which the flare should be visible. The brightness fades from 0-100% between Outer and Inner Field of View.
Inner Field of View
The angle in degrees of which the flare should have full brightness.
Min Range
The minimum range for when the lens flare is visible. A value of -1 means that the camera can never be to close.
Max Range
The maximum range for when the lens flare is visible. A value of -1 means that the lens flare has an unlimited range.
Size change based on distance
A real value between 0-1 that determines how much the screen size of the lens flare should change the further away it gets. A value of 0 means that the flare always has same size on the screen.
Lens flares can be used to blind the camera. Either if the camera is looking directly at the lens flare or if the lens flare is pointed toward the camera.
Glare Brightness
How much the camera will be blinded.
Glare Stare At
How blinded the camera will be by looking directly at the lens flare.
Glare Field of View
The angle in degrees of which the lens flare should blind the camera. The camera will be more blinded the more the lens flare pointed at the camera.
