Description

Evaluate an expression in LUA for each weightmap value, with up to 30 weightmaps connected.

How to apply

To create a new Weightmap and apply the lmExpressionMapOp on it, either select a X3DObject, a Primitive or a Cluster. To apply the operator on an existing weightmap, select the weightmap.
Then choose "lm Expression Map" from the lmWeightMapTools menu.

Exemple of use

In this exemple, the expression map is connected to a proximity map, and the result is the sum of the proximity map (w0) multiplied by 3 (v0), a random value (r) multiplied by 2 (a) and the position x (x) multiplied by 0.149 (b).
The result range is changed to map the target [-1:1]. The negative values appears red (see the Tips section to learn how to get that color).

lmExpressionMap Operator Parameters

• Enable
  Main enable parameter. If not checked the operator is desactivated.
• General
  Expression: expression in LUA language, see the quick reference to see what's avalaible.
  Variable a, b: variables availaible in the expression.
  Random Seed: simple random seed.
  
• Post-Process
  Post-Process:
  None: nothing...
  Clamp: Clamp weight values between the Min and Max values.
  Change Range: change the range value to the specified range.
  Min, Max: Min and Max values of the Clamp and Change Range modes.
• Presets
  Negate: -w
  Invert: 1 - w
  Constrast: a - (a-w)*b
  Square: w^2
  Random: a*r
  Funky x: cond(y>0, r, a*r+b*x^2/2)
  Linear x, y, z: x, y, z
  Absolute X, Y, Z: math.abs(x), math.abs(y), math.abs(z)
  Radial XY, YZ, XYZ: x^2 + y^2, y^2 + z^2, x^2 + y^2 + z^2
• Transformation offsets
  These values define an offset transformation space for the values x, y, and z available in the expression.
• LUA Helpers
  You can define user LUA functions here. The exemple is the cond function, that behaves the same as the XSI expression cond.
  
• Add Connexion:
  This button launches a Custom Command that adds a connexion to the lmExpressionMapOp. You can either select one or more weightmaps and click on the button to add connexions to all the specified weightmaps, or you can select nothing and you will be asked to pick a weightmap.
• Remove All Connexions:
  This button launches a Custom Command that removes all the connexions from the operator.
• Weightmap group:
  w[i]: enable or disable the use of the connected weightmap number i, define the name of the value available in the expression.
  Remove: this button lauches a Custom Command that removes the specified connexion.
  v[i]: a custom variable available in the expression.

Quick Expression Reference

You can find a full documentation of the LUA language on www.lua.org.
Classic operations are + - * /
Raise to power is ^
Available maths functions are:
       math.abs     math.acos    math.asin    math.atan    math.atan2
       math.ceil    math.cos     math.deg     math.exp     math.floor
       math.log     math.log10   math.max     math.min     math.mod
       math.pow     math.rad     math.sin     math.sqrt    math.tan
       math.frexp   math.ldexp   math.random  math.randomseed
Available variables are:
       w: original weightmap value
       a, b: parameters animatable in XSI
       r: random value
       x, y, z: local position of the underlying geometry
       for each connected weightmap of index i:
             wi: connected weightmap value
             vi: parameter animatable in XSI