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<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
'http://www.w3.org/TR/html4/strict.dtd'>
<html lang="en">
<head>
<title>CSS 3D Transforms</title>
<link rel="stylesheet" type="text/css" href="../default.css">
<style type="text/css">
.rhs { white-space: pre-wrap; }
code { font-size: inherit; }
#box-shadow-samples td { background: white; color: black; }
</style>
<link rel="stylesheet" type="text/css"
href="http://www.w3.org/StyleSheets/TR/W3C-WD.css">
</head>
<body>
<div class="head">
<!--logo-->
<h1>CSS 3D Transforms</h1>
<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
<dt>This version:
<dd>
<a href="[VERSION]">http://dev.w3.org/csswg/css3-3d-transforms/</a>
<!--http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]-->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-3d-transforms/">[LATEST]</a>
<dt>Previous version:
<dd><a href="http://www.w3.org/TR/2009/WD-css3-3d-transforms-20090320/">
http://www.w3.org/TR/2009/WD-css3-3d-transforms-20090320/</a>
<dt id="editors-list">Editors:
<dd><a href="mailto:dino@apple.com">Dean Jackson</a> (<a
href="http://www.apple.com/">Apple Inc</a>)
<dd><a href="mailto:hyatt@apple.com">David Hyatt</a> (<a
href="http://www.apple.com/">Apple Inc</a>)
<dd><a href="mailto:cmarrin@apple.com">Chris Marrin</a> (<a
href="http://www.apple.com/">Apple Inc</a>)
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id="abstract">Abstract</h2>
<p>CSS 3D Transforms extends CSS Transforms to allow elements rendered by CSS to be transformed
in three-dimensional space.
<h2 class="no-num no-toc" id="status">Status of this document</h2>
<p class="note">
This will be the last published Working Draft of this specification. Work
will continue with a combined CSS and SVG Transforms specification operating
under the FX Taskforce. The latest <a href="http://dev.w3.org/csswg/css3-transforms/">
Editors' Draft</a> of the new specification is available.
</p>
<!--status-->
<p>
The <a href="ChangeLog">list of changes made to this specification</a> are
available.
</p>
<h2 class="no-num no-toc" id="contents">Table of contents</h2>
<!--toc-->
<h2 id="introduction">Introduction</h2>
<p><em>This section is not normative.</em>
<p>
This is an enhancement to the CSS
Transforms specification which provides transforms in three
dimensions. It should be read in conjunction with that specification.
</p>
<p>
This coordinate space can be modified with the <span
class="prop-name">'transform'</span> property. Using transform, elements
can be translated, rotated and scaled in two or three dimensional space.
A perspective transform can also be applied to give a sense of depth to
the way elements are displayed. In three
dimensions, a Z axis is added, with positive z values conceptually
rising perpendicularly out of the window toward the user and negative z
values falling into the window away from the user.
</p>
<p>
Any value other than 'none' for the transform results in the creation of
both a stacking context and a containing block. The object acts as
though position: relative has been specified, but also acts as a
containing block for fixed positioned descendants. The position on the Z
axis of a transformed element does not affect the order within a
stacking context. With elements at the same z-index, objects are drawn
in order of increasing z position.
</p>
<p>
Note that while <span class="prop-name">'transform'</span> uses a
three-dimensional coordinate system, the elements themselves are not
three-dimensional objects. Instead, they exist on a two-dimensional
plane (a flat surface) and have no depth.
</p>
<h2 id="transform-property">
The <span class="prop-name">'transform'</span> Property
</h2>
<p>
A 2D or 3D transformation is applied to an element through the <span
class="prop-name">'transform'</span> property. This property contains a
list of <a href="#transform-functions">transform functions</a>. The
final transformation value for an element is obtained by performing a
matrix concatenation of each entry in the list. The set of transform
functions is similar to those allowed by SVG. There are additional
functions to support 3D transformations.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="effects">transform</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
none | <transform-function> [ <transform-function> ]*
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
none
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percentages:</em>
</td>
<td>
refer to the size of the element's box
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
Same as specified value.
</td>
</tr>
</tbody>
</table><!-- ======================================================================================================= -->
<h2 id="transform-origin-property">
The <span class="prop-name">'transform-origin'</span> Property
</h2>
<p>
The <span class="prop-name">'transform-origin'</span> property
establishes the origin of transformation for an element. This property
is applied by first translating the element by the negated value of the
property, then applying the element's transform, then translating by the
property value. This effectively moves the desired transformation origin
of the element to (0,0,0) in the local coordinate system, then applies
the element's transform, then moves the element back to its original
position. Note that percentage values are not allowed in the z value.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="transform-origin">transform-origin</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
[ [ [ <percentage> | <length> | left | center | right ] [
<percentage> | <length> | top | center | bottom ]? ] <length> ] | [ [ [ left |
center | right ] || [ top | center | bottom ] ] <length> ]
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
50% 50% 0
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percentages:</em>
</td>
<td>
refer to the size of the element's box
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
For <length> the absolute value, otherwise a percentage
</td>
</tr>
</tbody>
</table>
<!-- ======================================================================================================= -->
<h2 id="transform-style-property">
The <span class="prop-name">'transform-style'</span> Property
</h2>
<p>
The <span class="prop-name">'transform-style'</span> property defines how nested elements are rendered in 3D space. If the <span class="prop-name">'transform-style'</span> is <span class="prop-value">'flat'</span>, all children of this element are rendered flattened into the 2D plane of the element. Therefore, rotating the element about the X or Y axes will cause children positioned at positive or negative Z positions to appear on the element's plane, rather than in front of or behind it. If the <span class="prop-name">'transform-style'</span> is <span class="prop-value">'preserve-3d'</span>, this flattening is not performed, so children maintain their position in 3D space.
</p>
<p>
This flattening takes place at each element, so preserving a hierarchy
of elements in 3D space requires that each ancestor in the hierarchy
have the value <span class="prop-value">'preserve-3d'</span> for <span
class="prop-name">'transform-style'</span>. But since <span
class="prop-name">'transform-style'</span> affects only an element's
children, the leaf nodes in a hierarchy do not require the perspective
style.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="transform-style">transform-style</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
flat | preserve-3d
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
flat
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percen
A0B2
tages:</em>
</td>
<td>
N/A
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
Same as specified value.
</td>
</tr>
</tbody>
</table>
<p>
For some effects, the author will have to ensure that an ancestor
element to a subtree using <span class="prop-value">'preserve-3d'</span>
has a <span class="prop-name">'transform-style'</span> of <span
class="prop-value">'flat'</span> (or the default). Otherwise, the
elements in the 3D tree may be located behind ancestor elements and,
thus, invisible (hidden behind an ancestor's background).
</p>
<p>
Note that while 'preserve-3d' can be specified on an element, the effect may not
be possible. Elements that have <span class="prop-name">'overflow'</span> set to
<span class="prop-value">'hidden'</span> are unable to keep their children in 3D.
In this case the element will behave as if the property was set to
<span class="prop-value">'flat'</span>.
</p>
<div class="issue">
Does transform-style: preserve-3d need to establish a stacking context
and containing block like transform does?
</div><!-- ======================================================================================================= -->
<h2 id="perspective-property">
The <span class="prop-name">'perspective'</span> Property
</h2>
<p>
The <span class="prop-name">'perspective'</span> property applies the
same transform as the <span
class="prop-value">perspective(<length>)</span> transform
function, except that it applies only to the positioned or transformed
children of the element, not to the transform on the element itself.
<p>
If the value is <span
class="prop-value">'none'</span>, less than or equal to 0 no perspective transform is applied.
</p>
<p>
The use of this property with any value other than 'none' establishes a
stacking context. It also establishes a containing block (somewhat
similar to position:relative), just like the 'transform' property does.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="perspective">perspective</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
none | <length>
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
none
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percentages:</em>
</td>
<td>
N/A
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
Same as specified value.
</td>
</tr>
</tbody>
</table><!-- ======================================================================================================= -->
<h2 id="perspective-origin-property">
The <span class="prop-name">'perspective-origin'</span> Property
</h2>
<p>
The <span class="prop-name">'perspective-origin'</span> property
establishes the origin for the <em>perspective</em> property. It
effectively sets the X and Y position at which the viewer appears to be
looking at the children of the element.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="perspective-origin">perspective-origin</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
[ [ <percentage> | <length> | left | center | right ] [
<percentage> | <length> | top | center | bottom ]? ] | [ [ le
42E
ft |
center | right ] || [ top | center | bottom ] ]
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
50% 50%
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percentages:</em>
</td>
<td>
refer to the size of the elemen's box
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
Same as specified value.
</td>
</tr>
</tbody>
</table><!-- ======================================================================================================= -->
<h2 id="backface-visibility-property">
The <span class="prop-name">'backface-visibility'</span> Property
</h2>
<p>
The <span class="prop-name">'backface-visibility'</span> property
determines whether or not the "back" side of a transformed element is
visible when facing the viewer. With an identity transform, the front
side of an element faces the viewer. Applying a rotation about Y of 180
degrees (for instance) would cause the back side of the element to face
the viewer.
</p>
<p>
This property is useful when you place two elements back-to-back, as you
would to create a playing card. Without this property, the front and
back elements could switch places at times during an animation to flip
the card. Another example is creating a box out of 6 elements, but where
you want to see the inside faces of the box. This is useful when
creating the backdrop for a 3 dimensional stage.
</p>
<table class="propdef">
<tbody>
<tr>
<td>
<em>Name:</em>
</td>
<td>
<dfn id="backface-visibility">backface-visibility</dfn>
</td>
</tr>
<tr>
<td>
<em>Value:</em>
</td>
<td>
visible | hidden
</td>
</tr>
<tr>
<td>
<em>Initial:</em>
</td>
<td>
visible
</td>
</tr>
<tr>
<td>
<em>Applies to:</em>
</td>
<td>
block-level and inline-level elements
</td>
</tr>
<tr>
<td>
<em>Inherited:</em>
</td>
<td>
no
</td>
</tr>
<tr>
<td>
<em>Percentages:</em>
</td>
<td>
N/A
</td>
</tr>
<tr>
<td>
<em>Media:</em>
</td>
<td>
visual
</td>
</tr>
<tr>
<td>
<em>Computed value:</em>
</td>
<td>
Same as specified value.
</td>
</tr>
</tbody>
</table><!-- ======================================================================================================= -->
<h2 id="transform-functions">
The Transformation Functions
</h2>
<p>
The value of the <span class="prop-name">transform</span> property is a
list of <transform-functions>, applied in the order provided. The
individual transform functions are separated by whitespace. The
following is a list of allowed transform functions. In this list the
type <translation-value> is defined as a <length> or
<percentage> value, and the <angle> type is defined by <a
href="http://www.w3.org/TR/css3-values/">CSS Values and Units.</a>
</p>
<dl>
<dt>
<span class="prop-value">matrix(<number>, <number>, <number>, <number>, <number>, <number>)</span>
</dt>
<dd>
specifies a 2D transformation in the form of a <a href="http://www.w3.org/TR/SVG/coords.html#TransformMatrixDefined">transformation matrix</a> of six values. <span class="prop-value">matrix(a,b,c,d,e,f)</span> is equivalent to matrix3d(a, b, 0, 0, c, d, 0, 0, 0, 0, 1, 0, e, f, 0, 1).
</dd>
<dt>
<span class="prop-value">matrix3d(<number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>, <number>)</span>
</dt>
<dd>
specifies a 3D transformation as a 4x4 homogeneous matrix of 16 values in column-major order.
</dd>
<dt>
<span class="prop-value">translate(<translation-value>[, <translation-value>])</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#TranslationDefined">2D translation</a> by the vector [tx, ty], where tx is the first translation-value parameter and ty is the optional second translation-value parameter. If <em><ty></em> is not provided, ty has zero as a value.
</dd>
<dt>
<span class="prop-value">translate3d(<translation-value>, <translation-value>, <translation-value>)</span>
</dt>
<dd>
specifies a 3D translation by the vector [tx,ty,tz], with tx, ty and tz being the first, second and third translation-value parameters respectively. Note that <percentage> values are not allowed in the tz translation-value, and if present will cause the propery value to be invalid.
</dd>
<dt>
<span class="prop-value">translateX(<translation-value>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#TranslationDefined">translation</a> by the given amount in the X direction.
</dd>
<dt>
<span class="prop-value">translateY(<translation-value>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#TranslationDefined">translation</a> by the given amount in the Y direction.
</dd>
<dt>
<span class="prop-value">translateZ(<translation-value>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#TranslationDefined">translation</a> by the given amount in the Z direction. Note that <percentage> values are not allowed in the translateZ translation-value, and if present will cause the propery value to be invalid.
</dd>
<dt>
<span class="prop-value">scale(<number>[, <number>])</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#ScalingDefined">2D scale</a> operation by the [sx,sy] scaling vector described by the 2 parameters. If the second parameter is not provided, it is takes a value equal to the first.
</dd>
<dt>
<span class="prop-value">scale3d(<number>, <number>, <number>)</span>
</dt>
<dd>
specifies a 3D scale operation by the [sx,sy,sz] scaling vector described by the 3 parameters.
</dd>
<dt>
<span class="prop-value">scaleX(<number>)</span>
</dt>
<dd>
specifies a scale operation using the [sx,1,1] scaling vector, where sx is given as the parameter.
</dd>
<dt>
<span class="prop-value">scaleY(<number>)</span>
</dt>
<dd>
specifies a scale operation using the [1,sy,1] scaling vector, where sy is given as the parameter.
</dd>
<dt>
<span class="prop-value">scaleZ(<number>)</span>
</dt>
<dd>
specifies a scale operation using the [1,1,sz] scaling vector, where sz is given as the parameter.
</dd>
<dt>
<span class="prop-value">rotate(<angle>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#RotationDefined">2D rotation</a> by the angle specified in the parameter about the origin of the element, as defined by the <em>transform-origin</em> property.
</dd>
<dt>
<span class="prop-value">rotate3d(<number>, <number>, <number>, <angle>)</span>
</dt>
<dd>
specifies a clockwise 3D rotation by the angle specified in last
parameter about the [x,y,z] direction vector described by the first 3
parameters. If the direction vector is not of unit length, it will be
normalized. A direction vector that cannot be normalized, such as [0,
0, 0], will cause the rotation to not be applied. This function is
equivalent to <code>matrix3d(1 + (1-cos(angle))*(x*x-1), -z*sin(angle)+(1-cos(angle))*x*y, y*sin(angle)+(1-cos(angle))*x*z, 0, z*sin(angle)+(1-cos(angle))*x*y, 1 + (1-cos(angle))*(y*y-1), -x*sin(angle)+(1-cos(angle))*y*z, 0, -y*sin(angle)+(1-cos(angle))*x*z, x*sin(angle)+(1-cos(angle))*y*z, 1 + (1-cos(angle))*(z*z-1), 0, 0, 0, 0, 1)</code>.</dd>
<dt>
<span class="prop-value">rotateX(<angle>)</span>
</dt>
<dd>
specifies a clockwise rotation by the given angle about the X axis.
</dd>
<dt>
<span class="prop-value">rotateY(<angle>)</span>
</dt>
<dd>
specifies a clockwise rotation by the given angle about the Y axis.
</dd>
<dt>
<span class="prop-value">rotateZ(<angle>)</span>
</dt>
<dd>
specifies a clockwise rotation by the given angle about the Z axis.
</dd>
<dt>
<span class="prop-value">skewX(<angle>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#SkewXDefined">skew transformation along the X axis</a> by the given angle.
</dd>
<dt>
<span class="prop-value">skewY(<angle>)</span>
</dt>
<dd>
specifies a <a href="http://www.w3.org/TR/SVG/coords.html#SkewYDefined">skew transformation along the Y axis</a> by the given angle.
</dd>
<dt>
<span class="prop-value">skew(<angle> [, <angle>])</span>
</dt>
<dd>
specifies a <a
href="http://www.w3.org/TR/SVG/coords.html#SkewXDefined">skew
transformation along the X and Y axes</a>. The first angle parameter
specifies the skew on the X axis. The second angle parameter specifies
the skew on the Y axis. If the second parameter is not given then a
value of 0 is used for the Y angle (ie. no skew on the Y axis).
</dd>
<dt>
<span class="prop-value">perspective(<length>)</span>
</dt>
<dd>
specifies a perspective projection matrix. This matrix maps a <em>viewing cube</em> onto a pyramid whose
base is infinitely far away from the viewer and whose peak represents the viewer's position. The
viewable area is the region bounded by the four edges of the viewport (the portion of the browser
window used for rendering the webpage between the viewer's position and a point at a distance of
infinity from the viewer). The <em>depth</em>, given as the parameter to the function, represents the
distance of the z=0 plane from the viewer. Lower values give a more flattened pyramid and
therefore a more pronounced perspective effect. For example, a value of 1000px
gives a moderate amount of foreshortening and a value of 200px gives an extreme amount. The matrix
is computed by starting with an identity matrix and replacing the value at row 3, column 4 with
the value -1/depth. The value for depth must be greater than zero, otherwise the function is invalid.
</dd>
</dl>
<!-- ======================================================================================================= -->
<h2 id="animation">
Transitions and animations between transform values
</h2>
<p>
When animating or transitioning the value of a transform property
the rules described below are applied. The 'from' transform is
the transform at the start of the transition or current keyframe. The
'end' transform is the transform at the end of the transition or
current keyframe.
</p>
<ul>
<li>
If the 'from' and 'to' transforms are both single functions
of the same type:
<ul>
<li>
For translate, translate3d, translateX, translateY, translateZ, scale,
scale3d, scaleX, scaleY, scaleZ, rotate, rotateX, rotateY, rotateZ, skewX
and skewY functions:
<ul>
<li>
the individual components of the function are
interpolated numerically.
</li>
</ul>
</li>
<li>
For perspective, matrix, matrix3d and rotate3d:
<ul>
<li>
the values are first converted to a 4x4 matrix, then
decomposed using <a
href="http://tog.acm.org/GraphicsGems/gemsii/unmatrix.c">the
method described by unmatrix</a> into separate translation,
scale, rotation, skew and perspective matrices, then each
decomposed matrix is interpolated numerically, and finally
combined in order to produce a resulting 4x4 matrix.
</li>
</ul>
</li>
</ul>
</li>
<li>
If both the 'from' and 'to' transforms are "none":
<ul>
<li>
There is no interpolation necessary
</li>
</ul>
</li>
<li>
If one of the 'from' or 'to' transforms is "none":
<ul>
<li>
The 'none' is replaced by an equivalent identity function list for
the corresponding transform function list.
<p>
For example, if the 'from' transform is "scale(2)" and the 'to'
transform is "none" then the value "scale(1)" will be used as the
'to' value, and animation will proceed using the rule above.
Similarly, if the 'from' transform is "none" and the 'to' transform
is "scale(2) rotate(50deg)" then the animation will execute as
if the 'from' value is "scale(1) rotate(0)".
</p>
<p>
The identity functions are translate(0), translate3d(0, 0, 0),
translateX(0), translateY(0), translateZ(0), scale(1), scale3d(1, 1, 1),
scaleX(1), scaleY(1), scaleZ(1), rotate(0), rotate3d(1, 1, 1, 0),
rotateX(0), rotateY(0), rotateZ(0), skewX(0), skewY(0),
matrix(1, 0, 0, 1, 0, 0) and
matrix3d(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1).
</p>
</li>
</ul>
</li>
<li>
If both the 'from' and 'to' transforms have the same number of
transform functions and corresponding functions in each transform
list are of the same type:
<ul>
<li>
Each transform function is animated with its corresponding
destination function in isolation using the rules described above.
The individual values are then applied as a list to produce
resulting transform value.
</li>
</ul>
</li>
<li>
Otherwise:
<ul>
<li>
The transform function lists are each converted into the
equivalent matrix3d value and animation proceeds using the rule
for a single function above.
</li>
</ul>
</li>
</ul>
<!-- ======================================================================================================= -->
<h2 id="rendering-3d">
Rendering in 3d
</h2>
<p>
Since CSS only describes a flat rendering model, without perspective, and where everything
faces the viewer front on, once three-dimensional transforms are supported it is necessary
to describe how an element should be drawn in different orientations.
</p>
<p>
While CSS specifies a rendering order for properties, such as background, border and content,
this rendering order does not imply any three-dimensional structure. That is, if an element
is rotated so that its back face is facing the user, it will appear like a mirrored version
of the front face. In other words, the transforms are applied to the rendered version
of the elements, as if the element is rendered into an offscreen buffer, and that buffer is
transformed and composited onto the page.
</p>
<!-- ======================================================================================================= -->
<h2 id="dom-interfaces">
DOM Interfaces
</h2>
<p>
This section describes the interfaces and functionality added to the DOM to support runtime access to the functionality described above.
</p>
<!-- ============================================================ -->
<h3 id="cssmatrix-interface">
Extensions to CSSMatrix
</h3>
<dl>
<dt>
<b>Interface <i><a id="DOM-CSSMatrix" name='DOM-CSSMatrix'>CSSMatrix</a></i></b>
</dt>
<dd>
<p>
The following extends the <code>CSSMatrix</code> interface definition specified in
the CSS3 2D Transforms Module.
</p>
<dl>
<dt>
<b>IDL Definition</b>
</dt>
<dd>
<div class='idl-code'>
<pre>
[Supplemental] interface CSSMatrix {
attribute float m11;
attribute float m12;
attribute float m13;
attribute float m14;
attribute float m21;
attribute float m22;
attribute float m23;
attribute float m24;
attribute float m31;
attribute float m32;
attribute float m33;
attribute float m34;
attribute float m41;
attribute float m42;
attribute float m43;
attribute float m44;
CSSMatrix translate(in float x, in float y, optional in float z);
CSSMatrix scale(in float scaleX, optional in float scaleY, optional in float scaleZ);
CSSMatrix rotate(in float rotX, optional in float rotY, optional in float rotZ);
CSSMatrix rotateAxisAngle(in float x, in float y, in float z, in float angle);
};</pre>
</div><br>
</dd> <!-- IDL -->
<dt>
<b>Attributes</b>
</dt>
<dd>
<dl>
<dt>
<code class='attribute-name'><a id="DOM-CSSMatrix-matrix" name='DOM-CSSMatrix-matrix'>m11-m44</a></code> of type <code>float</code>
</dt>
<dd>
Each of these attributes represents one of the values in the 4x4 matrix. For instance m12 represents the value in the 2nd
column of the first row.<br>
</dd>
</dl>
</dd> <!-- Attributes -->
<dt>
<b>Methods</b>
</dt>
<dd>
<dl>
<!-- ===================================================== -->
<dt>
<code class='method-name'><a id="DOM-CSSMatrix-translate" name='DOM-CSSMatrix-translate'>translate</a></code>
</dt>
<dd>
<div class='method'>
The <code>translate</code> method returns a new matrix which is this matrix post multiplied by a translation matrix containing the passed values. If the z component is undefined, a 0 value is used in its place. This matrix is not modified.
<div class='parameters'>
<b>Parameters</b>
<div class='paramtable'>
<dl>
<dt>