[x3d-public] Proposal: expressions

[Joe D Williams]

> has never been seriously considered

well, i didn't mean not considered seriously, but rather seriously 
considered along with other concepts that VRML and X3D does not use. 
Mainly declined, I believe, because to do the thing could possibly 
impair authortime and runtime validation steps. Also, the X3D event 
utilities were born due to some of the considerations you describe.

Thanks and Best,
Joe



----- Original Message ----- 
From: "Joe D Williams" <joedwil at earthlink.net>
To: "Yves Piguet" <yves.piguet at gmail.com>; "X3D Graphics public 
mailing list" <x3d-public at web3d.org>
Sent: Monday, September 12, 2016 10:26 AM
Subject: Re: [x3d-public] Proposal: expressions


> Hi Yves,
> Can you compare these examples with how it would be done using the 
> script node in the prototype instead of the 'simple' expression 
> using inline maths? Also, can you show the rest of the user code 
> that declares and instances the proto and shows any routes?
>
> I remember discussions of using an expression inline in a proto as 
> you show to avoid a script, and also even expressions in the main 
> user code to avoid some simple scripts and prototypes, and that this 
> step has never been seriously considered. Maybe your examples with 
> proto could help get some support from a second independent 
> implementation. Have you looked at how this would could work in the 
> x3d in html integration?
>
> Thanks and Best,
> Joe
>
>
>
> ----- Original Message ----- 
> From: "Yves Piguet" <yves.piguet at gmail.com>
> To: "X3D Graphics public mailing list" <x3d-public at web3d.org>
> Sent: Monday, September 12, 2016 2:36 AM
> Subject: [x3d-public] Proposal: expressions
>
>
> Hi,
>
> In prototypes, there is often a need for simple expressions to set 
> field values. For instance in a toggle switch, the most obvious type 
> for its state is an SFBool which cannot be used directly to change 
> the switch position (SFVec3f translation), angle (SFRotation 
> orientation) or light (SFNode material). Likewise there is a Switch 
> node where the active child is selected with an SFInt32, which 
> provides a lot of flexibility but doesn't match directly the most 
> frequent case, a boolean value. Currently, the only solution is 
> scripts with node references (DEF/USE) or routes (DEF/ROUTE).
>
> I suggest to add expressions as an intermediate possibility between 
> scripts and direct IS references. I'll use the Classic notation.
>
> Wherever "IS name" is permitted, the syntax "(expr)" stands for an 
> expression which must be evaluated the first time the scene is 
> rendered and when the values it refers to change.
>
> For the syntax, instead of JavaScript which quickly becomes verbose 
> with "Math." namespace and objects, I propose what follows. This 
> should cover the intended applications.
>
> Types:
> - number, compatible with all X3D scalar numbers: SFFloat, SFInt32, 
> SFTime...
> - boolean
> - string
> - node (reference to X3D fields), including null
> - 1D array (syntax: [a,b,c,...]; compatible with all array-like X3D 
> types (SFVec3f, SFColor, SFMatrix3f etc.) and MF* (including 
> MFBoolean, MFString and MFNode), flatten
>
> Operators:
> - arithmetic +-*/% ^ (power), +- also as prefix operators, + also 
> for string concatenation
> - comparison == != < > <= >=
> - logical && ||
> - conditional ?:
> - same precedence as JS with parenthesized subexpressions
>
> Functions:
> - trig: sin cos tan asin acos atan atan2
> - log: log log10 exp
> - misc. math: abs round floor ceil sqrt
> - logical: xor
> - string: tbd (at least conversion from numbers with toFixed(x,n))
>
> Values:
> - literal numbers and strings with X3D syntax
> - true false null (lowercase)
> - prototype field names for initializeOnly and inputOutput
>
> Example 1: led with boolean state:
>
> #X3D V3.3 utf8
>
> PROTO Led [
>  inputOutput SFVec3f size 2 2 2
>  inputOutput SFColor diffuseColor 0.2 0.2 0.2
>  inputOutput SFColor emissiveColor 0 1 0
>  inputOutput SFBool state FALSE
> ] {
>  Shape {
>    geometry Box {
>      size IS size
>    }
>    appearance Appearance {
>      material Material {
>        diffuseColor IS diffuseColor
>        emissiveColor (state ? emissiveColor : [0, 0, 0])
>      }
>    }
>  }
> }
>
> Led {
>  diffuseColor 0.3 0.1 0.1
>  emissiveColor 1 0 0
>  state TRUE
> }
>
> Example 2: gauge with two cylindric parts and a total height, where 
> the ratio of the first part is specified with an SFFloat field 
> "value":
>
> #X3D V3.3 utf8
>
> PROTO Gauge [
>  inputOutput SFFloat height 2
>  inputOutput SFFloat radius 1
>  inputOutput SFNode appearance1 NULL
>  inputOutput SFNode appearance2 NULL
>  inputOutput SFFloat value 0.5
> ] {
>  Group {
>    children [
>      Transform {
>        translation ([0, (1 - value) * height / 2, 0])
>        children Shape {
>          geometry Cylinder {
>            radius IS radius
>            height (value * height)
>          }
>          appearance IS appearance1
>        }
>      }
>      Transform {
>        translation ([0, -value * height / 2, 0])
>        children Shape {
>          geometry Cylinder {
>            radius IS radius
>            height ((1 - value) * height)
>          }
>          appearance IS appearance2
>        }
>      }
>    ]
>  }
> }
>
> Gauge {
>  appearance1 Appearance {
>    material Material {
>      diffuseColor 1 0 0
>    }
>  }
>  appearance2 Appearance {
>    material Material {
>      diffuseColor 0 0.8 0
>    }
>  }
>  value 0.7
> }
>
> Example 3: torsion shaft, a cylinder with different rotations for 
> top and bottom with a texture which shows the torsion (requires a 
> TextureMatrixTransform node with an arbitrary 2D SFMatrix3f 
> transform matrix; url "texture:checkerboard" refers to a 2x2 
> checkerboard image)
>
> #X3D V3.3 utf8
>
> PROTO TorsionShaft [
>  initializeOnly SFFloat radius 1
>  inputOutput SFFloat height 2
>  initializeOnly SFBool solid TRUE
>  initializeOnly SFNode material NULL
>  initializeOnly SFFloat textureScale 1
>  inputOutput SFFloat bottomRotation 0
>  inputOutput SFFloat topRotation 0
> ] {
>  Transform {
>    rotation ([0, 1, 0, bottomRotation])
>    Shape {
>      Appearance {
>        ImageTexture {
>          url "texture:checkerboard"
>        }
>        TextureMatrixTransform {
>          matrix ([
>            textureScale,
>            textureScale * (bottomRotation - topRotation) / 2 / pi,
>            0,
>            0, 0, 0,
>            0, 0, 1
>          ])
>        }
>        material IS material
>      }
>      Cylinder {
>        radius IS radius
>        height IS height
>        top FALSE
>        bottom FALSE
>        solid IS solid
>      }
>    }
>  }
> }
>
> TorsionShaft {
>  textureScale 4
>  bottomRotation 0.1
>  topRotation 0.8
> }
>
> All examples have been tested in our experimental implementation. 
> I've attached snapshots for examples 2 and 3. Feedback welcome...
>
> Yves
>
>
>
>
> --------------------------------------------------------------------------------
>
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