Glen Whitney
92be417845
Set VRML97 translation of IndexedFaceSets to specify `solid false` unless the faces were explicitly indicated to have CLOCKWISE or COUNTERCLOCKWISE vertex ordering. This is conservative, but otherwise shapes may be "see-through" in undesirable ways, if the original VRML 1 vertices are not ordered consistently with the VRML97 default. Also fixes a typo/bug in picking up numerical values of parameters, and ensures that fields in the output VRML97 are always separated by at least a space, comma, or parenthesis.
77 lines
2.8 KiB
Markdown
77 lines
2.8 KiB
Markdown
# vrml1to97
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JavaScript converter from VRML 1.0 to VRML97 file format, based on Wings 3D
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conversion logic.
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Essentially, this is a JavaScript reimplementation of the algorithm of the
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"token rearranger" found in the
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[Wings 3D x3d importer](https://github.com/dgud/wings/blob/master/plugins_src/import_export/x3d_import.erl)
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(which was written in Erlang).
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## Usage
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From an es6 module under Node (for example)
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```js
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import {convert} from 'vrml1to97'
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const vrml1spec = '# VRML 1.0 ....'
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const vrml97spec = convert(vrml1spec)
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```
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or from a script in a webpage
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```js
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(async () => {
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const vrml1to97 = await import('./dist/vrml1to97/index.js')
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const vrml1spec = '# VRML 1.0 ....'
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const vrml97spec = vrml1to97.convert(vrml1spec)
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})()
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```
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or from the command line via node
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```shell
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npx vrml1to97 < old.wrl > shinynew.wrl
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```
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## API
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Currently this package exports just two functions:
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* convert(vrml1: string, source?: string): string
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The main function, takes in VRML 1 syntax (note that it does not
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actually check that its input is VRML 1, so its behavior is undefined
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if given anything but valid VRML 1 syntax). Returns VRML 97 syntax for
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the same scene, as nearly as it can translate. Note that not all of
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VRML 1 is recognized, and some of the translations may be somewhat
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approximate.
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If the optional second argument `source` is supplied, `convert` adds
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a comment indicating that the original vrml1 came from the specified
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source, before conversion to VRML97.
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* tree97(vrml1: string): Tree
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Takes the same input as convert, but rather than returning a string, it
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returns a very rough syntax tree for the converted VRML97 scene. The
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returned Tree data structure is an object whose keys are property names
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and whose values are lists of either strings or sub-Trees. Note however
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that this syntax tree does not represent a complete parse; since VRML 1
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and VRML97 are close, whole blocks of syntax are left as strings rather
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than broken into node names and property values. If there is a need to
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generate XML syntax output, for example, the code would need to be
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modified to break the tree down further to be ready for conversion to XML.
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## Conversion notes
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One sort of geometry common to VRML 1 and VRML97 is the IndexedFaceSet. These
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often used to render solids. Indeed, the default in VRML97 is to assume they
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do represent a solid, with the normals pointing outward. Unusual visual effects
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ensue if the normals are not properly directed (basically, you see through the
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"front" of the solid and see the "backs" of the faces on the opposite side).
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As a result, unless the input VRML 1 explicitly includes an explicit
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vertexOrdering of CLOCKWISE or COUNTERCLOCKWISE, the default solid treatment
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will be turned off in the VRML97 output, meaning that all faces will be
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rendered opaque in both directions.
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