The Moving Worlds VRML 2.0 Specification

Field Reference

Draft #2, May 30, 1996

This section provides a detailed description of field types in VRML 2.0. There is a helpful table of contents at the top organized functionally. However, the fields are listed alphabetically in this document. (An alphabetical Index of Nodes and Fields is also available.)

[TBD: Complete alphabetical listing and description]

There are two general classes of fields; fields that contain a single value (where a value may be a single number, a vector, or even an image), and fields that contain multiple values. Single-valued fields all have names that begin with SF, multiple-valued fields have names that begin with MF. Each field type defines the format for the values it writes.

Multiple-valued fields are written as a series of values separated by commas, all enclosed in square brackets. If the field has zero values then only the square brackets ("[]") are written. The last may optionally be followed by a comma. If the field has exactly one value, the brackets may be omitted and just the value written. For example, all of the following are valid for a multiple-valued field containing the single integer value 1:

1
[1,]
[ 1 ]

SFBool

A field containing a single boolean (true or false) value. SFBools are written as TRUE or FALSE.

SFColor/MFColor

Fields containing one (SFColor) or zero or more (MFColor) RGB colors. Each color is written to file as an RGB triple of floating point numbers in ANSI C floating point format, in the range 0.0 to 1.0. For example:

[ 1.0 0. 0.0, 0 1 0, 0 0 1 ]

is an MFColor field containing the three colors red, green, and blue.

SFFloat/MFFloat

Fields that contain one (SFFloat) or zero or more (MFFloat) single-precision floating point number. SFFloats are written to file in ANSI C floating point format. For example:

[ 3.1415926, 12.5e-3, .0001 ]

is an MFFloat field containing three values.

SFImage

A field that contain an uncompressed 2-dimensional color or greyscale image.

SFImages are written to file as three integers representing the width, height and number of components in the image, followed by width*height hexadecimal values representing the pixels in the image, separated by whitespace. A one-component image will have one-byte hexadecimal values representing the intensity of the image. For example, 0xFF is full intensity, 0x00 is no intensity. A two-component image puts the intensity in the first (high) byte and the transparency in the second (low) byte. Pixels in a three-component image have the red component in the first (high) byte, followed by the green and blue components (so 0xFF0000 is red). Four-component images put the transparency byte after red/green/blue (so 0x0000FF80 is semi-transparent blue). A value of 0xFF is completely transparent, 0x00 is completely opaque. Note: each pixel is actually read as a single unsigned number, so a 3-component pixel with value "0x0000FF" can also be written as "0xFF" or "255" (decimal). Pixels are specified from left to right, bottom to top. The first hexadecimal value is the lower left pixel of the image, and the last value is the upper right pixel.

For example,

1 2 1 0xFF 0x00

is a 1 pixel wide by 2 pixel high greyscale image, with the bottom pixel white and the top pixel black. And:

2 4 3 0xFF0000 0xFF00 0 0 0 0 0xFFFFFF 0xFFFF00

is a 2 pixel wide by 4 pixel high RGB image, with the bottom left pixel red, the bottom right pixel green, the two middle rows of pixels black, the top left pixel white, and the top right pixel yellow.

SFInt32/MFInt32

Fields containing one (SFInt32) or zero or more (MFInt32) 32-bit integers. SFInt32s are written to file as an integer in decimal or hexadecimal (beginning with '0x') format. For example:

[ 17, -0xE20, -518820 ]

is an MFInt32 field containing three values.

SFNode/MFNode

A field containing one or several nodes. An node field's syntax is just the node that it contains; for example, this is valid syntax for an MFNode field:

[ Transform { translation 1 0 0 }, DEF CUBE Cube { }, USE SOME_NODE ]

An SFNode field may also contain the keyword NULL to indicate that it contains nothing.

SFRotation/MFRotation

A field containing an arbitrary rotation. SFRotations are written to file as four floating point values separated by whitespace. The 4 values represent an axis of rotation followed by the amount of right-handed rotation about that axis, in radians. For example, a 180 degree rotation about the Y axis is:

0 1 0  3.14159265

SFString/MFString

Fields containing one (SFString) or zero or more (MFString) UTF-8 string (sequence of characters). Strings are written to file as a sequence of UTF-8 octets in double quotes. Any characters (including newlines and '#') may appear within the quotes. To include a double quote character within the string, precede it with a backslash. To include a backslash character within the string, type two backslashes. For example:

"One, Two, Three"
"He said, \"Immel did it!\""

are both valid strings.