Test Suite checks your browser's vision
- By Lynne S. Rosenthal
- Jun 30, 1997
Here's how to see for yourself which World Wide Web browser displays VRML 2.0 worlds
Different vendors' VRML products are supposed to be interoperable if they follow the
VRML 2.0 draft international standard, which defines features of .wrl files and sets
minimum browser requirements. You might expect compliant browsers to have at least the
same minimum capability and produce consistent results. But in the real world-or rather
virtual worlds-this is not so.
Anyone who has a Web client configured with a VRML 2.0 plug-in can test it using the
VRML Test Suite, which is freely accessible on the National Institute of Standards and
Technology's site at http://www.nist.gov/vrml.html1.
The suite consists of .wrl files that check the browser's abilities to produce correct
behaviors. Each test case corresponds to a .wrl file and describes the purpose and
expected result. Results are captured as GIF89 images for tests that involve static
scenes. Motion Picture Experts Group-compressed movies test animated scenes.
To view the VRML 2.0 standard as a Hypertext Markup Language document, visit http://www.vrml.org/VRML97/DIS/. Every
test case links to one or more requirements in VRML 2.0.
You can easily validate a test case by tracing its chain of inference back to specific
clauses in the standard as well as viewing the file source.
The first set of tests concentrates on static and "one node at a time"
techniques for two reasons. If a browser can't implement a simple file correctly, then it
won't be able to handle more complex worlds. Also, if many features are tested at the same
time, you might not know what didn't work correctly.
After these basic tests, the suite will move on to test multiple nodes, dynamic
behavior and complex interactive worlds.
Differences between browsers arise either from incorrect implementation of the standard
or from "legal" variations on standard behavior. Legal differences often come
from the underlying rendering software or the particular hardware on which the browser was
The textured cone test case, for example, applies a simple image texture to a cone. The
texture should wrap counterclockwise from above, starting at the back. A circle cutout of
the texture is applied right side up to the base of the cone when tilted toward the Z
Although there's a lot of variance in the way browsers wrap textures around the cone,
one popular browser wraps in the wrong direction-clockwise.
The test suite application itself consists of standard HTML pages with Common Gateway
Interface or Perl applications providing program logic, and database technology providing
the test suite documentation, data archiving and data retrieval.
The suite's three HTML frames make up a single test environment for a VRML 2.0 node's
specification, requirements and actual test worlds. Online help and documentation lead you
through the test cases.
Once in the application, you navigate through the hierarchy of the VRML 2.0 language,
beginning at the Node Group level and descending to the Node level.
After choosing a node, you see a menu of links to the available test cases, references
and test assertions. You can navigate up and down the VRML language tree to examine your
browser's compliance to other specifications.
To get started, here's how to test a VRML browser's implementation of the Color node:
From the Node frame at the left, select the Geometric Properties group. This will
update the selection window and present a list of all VRML nodes belonging to this group.
The screen's top banner frame contains links to the node specification reference,
requirements list and test cases. When you select Test Cases, you see the titles of the
tests as hyperlinks to the .wrl files. Your selected link spawns the current default VRML
browser plug-in and displays that browser's interpretation of the test world.
The suite's collection of VRML examples will help users understand the VRML language
and construct their own virtual worlds. Vendors also can use the suite to test their
products. VRML Consortium members are working with NIST to add new tests and enhancements
to the suite, which now has more than 500 test files.
Lynne S. Rosenthal works at NIST's Software Diagnostics and Conformance Testing
Division in Gaithersburg, Md.