matrix3x4_t

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matrix3x4_t is a C++ class that represents a matrix: a mathematical construct that allows Vectors to be transformed.

Matrices are chiefly used to rotate vectors, since translation and scaling are taken care of by vector addition and multiplication respectively. A single matrix can store a transformation in all four modes however, making them useful in transformation-intense operations like vertex rasterization.

The VMatrix class offers an additional row to use (4x4) and allows you to utilize a few different functions. Matrices of that dimension in source are mainly required to describe perspective transformations during rendering.

Functions

Generation

Matrix generation is best left to Source's pre-existing functions:

void AngleMatrix( QAngle angle, matrix_3x4_t& out ); // Rotation; can also use Quaternions or Radians
void PositionMatrix( Vector position, matrix3x4_t& out ); // Translation
void AngleMatrix( QAngle angle, Vector position, matrix3x4_t& out ); // Rotation + translation
void SetScaleMatrix( float scale, matrix3x4_t& out ); // Scale

Use MatrixMultiply() to combine two matrices into one. You can do this any number of times.

Application

Tip:Unless re-using an existing matrix you are better off rotating a vector with VectorRotate(), which accepts angles directly.

The mathematical notation for a matrix transformation is (vector * matrix). Source does not support that syntax, though it would be trivial to add if you so wanted, and instead offers these functions:

void VectorTransform( Vector in1, matrix3x4_t in2, Vector& out );
void VectorITransform( Vector in1, matrix3x4_t in2, Vector& out ); // 'Inverse' of the above

There is an overload of VectorRotate() that accepts a matrix3x4_t. It seems to behave in the same way as VectorTransform().

Other / utility

void MatrixAngles()
void MatrixPosition()
void MatrixVectors()
Extract angles and vectors from a matrix. MatrixAngles() has many overloads. There is no way to extract a scale.
void MatrixTranspose()
Transposes a matrix. This is useful to flip columns and rows of a matrix and a necessarity when communicating between systems that define matrix operations differently (like clientside code in source and shaders may do).
void MatrixInvert()
Reverses a matrix, making it transform in the opposite direction(s). You could also use VectorITransform() to apply the matrix.
bool MatricesAreEqual()
Instead of (matrix1 == matrix2).
void MatrixCopy()
Confirm:Instead of (matrix1 = matrix2).

See also