[x3d-public] Proposal: expressions
Don Brutzman
brutzman at nps.edu
Thu Sep 15 20:02:57 PDT 2016
Interesting ideas, thanks for sharing and exploring Yves! Definitely worthy of design scrutiny.
Some reactions:
- likely difficult to get existing base of players to adopt this kind of change, affects a player's scene parsing and scripting capabilities simultaneously.
- taking care to avoid over-mixing of presentation and content/computation.
- potential security considerations, dangers inherent in running dynamic code.
+ consider similarities to PHP, macros, other hybrid-programming constructs.
+ comparing compatible approaches with X3D Script node as well as HTML script code is helpful - in some sense you are simply moving the locations of expressions around, from page to scripts to scene (and perhaps from client to server).
+ might be considered a variant/superset of X3D, where a preprocessor takes your version and "expands macros" to create compliant X3D.
+ a Script node (or Prototype with embedded Script node) could take your expressions as an SFString field input and run javascript eval() function at run time.
One of the reasons that the X3D Working Group is working so hard this year on getting the object model, language bindings and encodings (such as JSON) completely "rock solid" is future potential use of X3D in just this kind of way - enabling higher-level language definitions that can be reduced to an X3D scene graph for interactive visualization. Another reason is to someday achieve "all X3D content can be fully validated, and so X3D players can be made to work correctly." Long-term expectation: the more that X3D scenes are able integrate with HTML5, the more people will try these kinds of evolutionary innovations.
Related work:
* Computer Graphics: From a Small Formula to Cyberworlds by Alexei Sourin (cc:ed), 3nd edition, Pearson Prentice Hall, Singapore, 385 pages, 2012. Chapter 14 discusses X3D and VRML (with an emphasis on functional representations, e.g. fVRML).
http://www3.ntu.edu.sg/home/assourin/fvrml.htm
I've copied Alexei who may have additional insights/interest. btw am further hoping to someday help adapt his language extensions into the .x3d XML syntax.
v/r Don
On 9/12/2016 2:22 PM, Yves Piguet wrote:
> On 12 sept. 2016, at 19:26, Joe D Williams wrote:
>
>> 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?
>
> I've added to the examples a version with Script nodes which should be compatible with X3D v3. I've also added explicit field names to the 3rd example.
>
> Yves
>
>
> Example 1: led with boolean state
>
> 1a. With expressions:
>
> #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
> }
>
> 1b. With a Script node:
>
> #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
> inputOnly SFBool set_state
> ] {
> Shape {
> geometry Box {
> size IS size
> }
> appearance Appearance {
> material DEF mat Material {
> diffuseColor IS diffuseColor
> }
> }
> }
> Script {
> initializeOnly SFNode mat USE mat
> initializeOnly SFColor emissiveColor IS emissiveColor
> initializeOnly SFColor black 0 0 0
> initializeOnly SFBool state IS state
> inputOnly SFBool set_state IS set_state
> url "javascript:
> function setEmissiveColor() {
> mat.emissiveColor = state ? emissiveColor : black;
> }
> function initialize() {
> setEmissiveColor();
> }
> function set_state(s) {
> state = s;
> setEmissiveColor();
> }
> "
> }
> }
>
> 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"
>
> 2a. With expressions:
>
> #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
> }
>
> 2b. With a Script node:
>
> #X3D V3.3 utf8
>
> PROTO Gauge [
> inputOutput SFFloat height 2
> inputOutput SFFloat radius 1
> inputOutput SFNode appearance1 NULL
> inputOutput SFNode appearance2 NULL
> initializeOnly SFFloat value 0.5
> inputOnly SFFloat set_value
> ] {
> Group {
> children [
> DEF t1 Transform {
> children Shape {
> geometry Cylinder {
> radius IS radius
> }
> appearance IS appearance1
> }
> }
> DEF t2 Transform {
> children Shape {
> geometry Cylinder {
> radius IS radius
> }
> appearance IS appearance2
> }
> }
> ]
> }
> Script {
> initializeOnly SFNode t1 USE t1
> initializeOnly SFNode t2 USE t2
> initializeOnly SFFloat height IS height
> initializeOnly SFFloat value IS value
> inputOnly SFFloat set_value IS set_value
> url "javascript:
> function setFields() {
> t1.translation = new SFVec3f(0, (1 - value) * height / 2, 0);
> cyl1.height = value * height;
> t2.translation = new SFVec3f(0, -value * height / 2, 0);
> cyl2.height = (1 - value) * height;
> }
> function initialize() {
> setFields();
> }
> function set_value(v) {
> value = v;
> setFields();
> }
> "
> }
> }
>
> 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)
>
> 3a. With expressions:
>
> #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
> }
>
> 3b. With a Script node:
>
> #X3D V3.3 utf8
>
> PROTO TorsionShaft [
> initializeOnly SFFloat radius 1
> initializeOnly SFFloat height 2
> initializeOnly SFBool solid TRUE
> initializeOnly SFNode material NULL
> initializeOnly SFFloat textureScale 1
> initializeOnly SFFloat bottomRotation 0
> initializeOnly SFFloat topRotation 0
> inputOnly SFFloat set_bottomRotation
> inputOnly SFFloat set_topRotation
> ] {
> DEF transform Transform {
> children Shape {
> appearance Appearance {
> texture ImageTexture {
> url "texture:checkerboard"
> }
> textureTransform DEF texTransform TextureMatrixTransform {
> matrix 1 0 0 0 0 0 0 0 1
> }
> material IS material
> }
> geometry Cylinder {
> radius IS radius
> height IS height
> top FALSE
> bottom FALSE
> solid IS solid
> }
> }
> }
> Script {
> initializeOnly SFFloat sc IS textureScale
> initializeOnly SFFloat bottomRotation IS bottomRotation
> initializeOnly SFFloat topRotation IS topRotation
> inputOnly SFFloat set_bottomRotation IS set_bottomRotation
> inputOnly SFFloat set_topRotation IS set_topRotation
> initializeOnly SFNode transform USE transform
> initializeOnly SFNode texTransform USE texTransform
> url "javascript:
> function setTextureTransform() {
> transform.rotation = new SFRotation(0, 1, 0, bottomRotation);
> texTransform.matrix[0] = sc;
> texTransform.matrix[1] = sc * (bottomRotation - topRotation) / 2 / Math.PI;
> }
> function initialize() {
> setTextureTransform();
> }
> function set_bottomRotation(a) {
> bottomRotation = a;
> setTextureTransform();
> }
> function set_topRotation(a) {
> topRotation = a;
> setTextureTransform();
> }
> "
> }
> }
>
> TorsionShaft {
> textureScale 4
> bottomRotation 0.1
> topRotation 0.8
> }
>
>
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all the best, Don
--
Don Brutzman Naval Postgraduate School, Code USW/Br brutzman at nps.edu
Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman
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