Writing Expressions

Scripts and expressions.

ZGameEditor has a very simple expression parser. The general syntax is based upon "C"-dialects.

The following syntax is supported.

Comments:

//this is a single line comment

/*

   this is a 
   multi line 
   comment

*/

Assignments:

[objectname].[propertyname].[propertyindex] = value ;

objectname - The name of a component is the value of its "Name"-property and is set in the editor. The special objectname "CurrentModel" can be used if the expression written has a Model-component as a parent.

propertyname - The name of the property to assign.

propertyindex - If the property is an indexed property, then the name of the index must be specified.

For Color-values, this is "R","G","B","A" for the Red/Green/Blue/Alpha components of the color in the range 0 to 1.

For position or vertex-values (such as Model.Position/Rotation/Velocity) the propertyindex is "X","Y","Z" for the value of its corresponding axis.

Example assignments:

PlayerModel.Position.X = 42;
PlayerModel.Position.X = PlayerModel.Position.Y / 2;
MyMaterial.Color.R = 0.5;

PlayerScore += 500;

Other C-style assignments are supported also:

• = - normal assignment
• += - plus-assign: x+=1 is the same as x=x+1
• -= - minus-assign: x-=1 is the same as x=x-1
• *= - multiply-assign: x*=1 is the same as x=x*1
• /= - divide-assign: x/=1 is the same as x=x/1

When assigning a property with several components (such as the x,y and z of Scale or Rotation) to the same value a shorter syntax is allowed.The following assigment:

CurrentModel.Scale=1;

Give the same result as:

CurrentModel.Scale.X=1;
CurrentModel.Scale.Y=1;
CurrentModel.Scale.Z=1;

IF-statements:

if( [condition] )

  [one line expression] ;

if( [condition] ) {

  //do something if condition is true

} else {

  //do something else if condition is false

}

condition - An expression which is evaluated to true or false.

Operators that are valid in conditions:

• == - equal
• != - not equal
• > - greater than
• >= - greater than or equal
• < - less than
• <= - less than or equal
• || - OR, statement is true if any of the conditions are true
• && - AND, statement is true if both conditions are true

Example IF-statements:

if(PlayerScore>5000)

  PlayerLives += 1;

if( (App.Time>5) && (PlayerLives<2) ) {

  Difficulty *= 1.2;
  Speed *= 1.2;  

}

Built in functions:

• sin(x) - returns the sine of the angle x in radians
• sqrt(x) - square root of x
• cos(x) - cosine of the angle x in radians.
• tan(x) - tangent of x
• abs(x) - absolute (positive) value of x
• rnd() - returns a random number in the range 0 to 1.
• random(base,variance) - random number in the range base-variance to base+variance
• atan2(y,x) - arctangent angle and quadrant of a given number
• noise2(x,y)
• noise3(x,y,z) - 2 and 3 dimensional Perlin Noise. Return values in an approximate range of -0.3 to 0.3 so you need to scale it to get a -1 to 1 range. More info: Hugo Elias article about noise.
• frac(x) - fractional (decimal) part of x
• exp(x) - the exponential of x
• clamp(x,min,max) - clamps the value x to be in the range min to max
• pow(base,exponent) - raises base to any power
• centerMouse() - centers the mouse cursor
• setRandomSeed(x) - set the random seed value to x, returns the old seed.
• floor(x) - returns the floor of x (the highest integer less than or equal to x)
• ceil(x) - returns the ceiling of x (the smallest integer larger than x)
• acos(x) - returns the inverse cosine of x
• asin(x) - returns the inverse sine of x

Predefined constants:

• PI