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.
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
MatrixMultiply() to combine two matrices into one. You can do this any number of times.
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
Other / utility
- Extract angles and vectors from a matrix.
MatrixAngles()has many overloads. There is no way to extract a scale.
- 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).
- Reverses a matrix, making it transform in the opposite direction(s). You could also use
VectorITransform()to apply the matrix.
- Instead of (matrix1 == matrix2).
- Confirm:Instead of (matrix1 = matrix2).