CEG:Operators
CEG Operators
Source
The engine source code which implements the CEG operators is viewable here:
Introduction
You are not limited to using fixed numbers in CEGs for positions, speeds, and so forth. Instead, you can use operators to change the CEG based on a variety of things.
Syntax
Operators are read left to right. The operand is always to the right of the operator. Spaces are ignored, except to separate numbers. A number with no operator defaults to addition.
The Buffer
CEG provides you with a buffer in which you can store numbers using the yank ('y') operator. This buffer can store 16 values, numbered 0 to 15.
Operators
These are listed in the format "Operator Name (operator)".
Index ('i')
Multiplies the operand by the current count index. This index starts at 0 and increments every time the spawn is run, until the spawn has run a number of times equal to its count.
Suggested use: Spawning things in a line.
Rand ('r')
Multiplies the operand by a random float between 0 and 1.
Suggested use: Keeping explosions from looking too "perfect", making explosions look different every time.
Damage ('d')
Multiplies the operand by damage.
CEG_DAMAGE: In a COB script, you can do SET CEG_DAMAGE [value]
. Any emit-sfx
instructions will then use that value for the "damage" (use the 'd' operator to access this value).
Sawtooth ('m')
Calculates the floating-point remainder of the operand.
Discrete ('k')
Calculates the floor of the operand.
Sine ('s')
Calculates the sine of the operand.
Yank ('y')
Saves the running result into buffer[operand], and resets the running result to zero.
Multiply ('x')
Multiplies the running result by buffer[operand].
Add Buffer ('a')
Adds buffer[operand] to the running result.
Power ('p')
Raises the running result to the operandth power
Power Buffer ('q')
Raises the running result to the buffer[operand]th power.
Add (default)
Adds the operand to the running result. This operator is used if no other operator is given.
Examples
Using 'r'
This is an example of a script that makes 10 smoke particles:
Heavy_Laser_Expl = {
smoke = {
water = true,
ground = true,
count = 10,
properties = {
-- age increase per frame, when age >= 1 the particle is destroyed
ageSpeed = 0.04,
size = 40,
sizeGrowth = -2,
pos = [[-30 r60, r30, -30 r60]],
speed = [[0.75 r-1.5, 1.7 r1.6, 0.75 r-1.5]],
},
},
}
For example in this snippet:
pos = [[-30 r60, r30, -30 r60]]
The x coordinate (specified with -30 r60
) will be:
x = -30 + (Random value between 0 and 60)
Using 'i'
Here is an example that uses the index (i) command in the properties:
heatcloud = {
ground = true,
count = 10,
properties = {
pos = [[0, i20, 0]],
heat = 10,
maxheat = 10,
heatFalloff = 1,
size = 30,
},
}
This script creates a tower of heatcloud projectile. The first projectile gets y=0
, the second y=20
, y=40
, y=60
, .. and finally y=180
.
Using 'x' and 'y'
i0.03125y0 -0.2x0x0
This multiplies the index by 0.03125
and saves it to buffer[0]
. It then multiplies -0.2
by buffer[0]
twice. The result is then -0.2 (i * 0.03125)^2
. This type of thing is useful for making a series of particles follow a curved path.