Class Name: Local 4x4
Subclasses
This DRM class is concrete and has no subclasses.
Definition
An instance of this DRM class specifies a 4×4 matrix that is
used to scale, orient, and position DRM objects in the scope of its
aggregate <LSR Transformation> instance.
The direction of rotation is determined by the right-hand rule. The
translation parameters are always in the rightmost column of the matrix.
Since a <Local 4x4> instance only appears as a
component of an <LSR Transformation>
instance and
an <LSR Transformation> instance only
appears in the scope of an LSR SRF, the DRM objects to which a
<Local 4x4> instance is applied are always
specified in an LSR SRF.
The matrix multiplication order is defined by
w =
M × v, where
M is the matrix of the <Local 4x4> instance,
v is the original location vector, and
w is the resulting location vector.
Primary Page in DRM Diagram:
Secondary Pages in DRM Diagram:
This class appears on only one page of the DRM class diagram.
Example
Let A be a <Model> instance representing an airport,
and let C be a separate <Model>
instance representing a control tower, where A
and C are specified in matching LSR SRFs,
and A contains a
<Geometry Model Instance> instance
G that is a reference to C.
G in A shall have
an <LSR Transformation> component, where the position and
orientation of the control tower G in
A is specified by the <Local 4x4>
component of that <LSR Transformation> instance.
FAQs
-
How is the transformation matrix specified?
The DRM specifies matrices in row major order; that is, the
first four elements correspond to the first row of the matrix, the
following four elements correspond to the second row of the matrix,
and so on (just as a float[4][4] in C is organized). Hence, if
mat[][] is the matrix being used, mat[i][j] is the element in
row i and column j of the matrix.
-
What is the multiplication order for the matrices of
<Local 4x4> instances?
If M is the transformation matrix of a
<Local 4x4> instance and v
is a column location vector,
the Level 0 API transforms v to a
column location vector w by setting
w =
M × v.
Figure 30 — <DRM Local 4x4> example
-
Is a matrix in the DRM the same as a matrix in OpenGL?
No. A matrix in the DRM is specified in row major order, while in OpenGL,
matrices are specified in column major order (as in the glMultMatrix
function). Consequently, to correctly apply DRM transformations in
OpenGL programs, each matrix shall be reordered.
Constraints
Component of (two-way)
Inherited Field Elements
This class has no inherited field elements.
Notes
Fields Notes
The matrix field specifies a
standard 4 × 4 transformation matrix.
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