Matrix Manual (Classic)

In 3D graphics a matrix is used to represent the transformation from one coordinate system to another. The typical use case is the transformation matrix that defines the position, rotation and scale of an object in 3D space.

The classic matrix classes available:

• Matrix32: A matrix composed of `Vector32` elements.
• Matrix64: A matrix composed of `Vector64` elements.
• Matrix: Defined as `Matrix64`.

Warning
A description of MAXON API matrix classes can be found here: Matrices.

# Access

To retrieve and modify Matrix objects stored in a BaseObject respectively use:

• BaseObject::GetMg(): Returns the world (global) matrix representing the object's position, scale and rotation.
• BaseObject::SetMg(): Sets the world (global) matrix representing the object's position, scale and rotation.

For more object related matrices see BaseObject.

To retrieve and modify Matrix objects stored in a BaseContainer respectively use:

To retrieve and modify Matrix objects stored in a GeData object (GeData type is DA_MATRIX) respectively use:

// This example reads a Matrix userdata parameter from the given object
// and creates a new cube using that Matrix.
GeData data;
// read the user data parameter 1
if (object->GetParameter(id, data, DESCFLAGS_GET::NONE))
{
const Matrix mg = data.GetMatrix();
if (cube != nullptr)
{
cube->SetMg(mg);
doc->InsertObject(cube, nullptr, nullptr);
}
}
Definition: c4d_baseobject.h:225
void SetMg(const Matrix &m)
Definition: c4d_baseobject.h:488
static BaseObject * Alloc(Int32 type)
Definition: lib_description.h:330
Definition: c4d_gedata.h:83
const Matrix & GetMatrix(void) const
Definition: c4d_gedata.h:457
@ DTYPE_MATRIX
Matrix
Definition: lib_description.h:71
@ DTYPE_SUBCONTAINER
Sub-container.
Definition: lib_description.h:58
#define Ocube
Cube.
Definition: ge_prepass.h:1095
#define ID_USERDATA
User data ID.
Definition: lib_description.h:25
const char * doc
Definition: pyerrors.h:226
Definition: object.h:105
Represents a level within a DescID.
Definition: lib_description.h:289

# Components

A matrix is composed of four vector components:

• Matrix::off: The translation vector.
• Matrix::sqmat::v1: The X-axis coordinate in a left-handed coordinate system of a transformed X-axis aligned unit-vector.
• Matrix::sqmat::v2: The Y-axis coordinate in a left-handed coordinate system of a transformed Y-axis aligned unit-vector.
• Matrix::sqmat::v3: The Z-axis coordinate in a left-handed coordinate system of a transformed Z-axis aligned unit-vector.
// This example prints the world space position of the given object.
const Matrix mg = object->GetMg();
ApplicationOutput("World Space Position: @"_s, mg.off);
#define ApplicationOutput(formatString,...)
Definition: debugdiagnostics.h:210
V off
The translation vector.
Definition: matrix.h:263

# Functionality

## Apply Transformation

A matrix is typically used to transform a given vector.

• Matrix::operator*() const: Transforms the given vector.
// This example loops through all points of the given point object.
// For each point the coordinates are transferred into world space
// and a sphere is created at that location.
const Vector* const points = pointObject->GetPointR();
const Int32 pointCount = pointObject->GetPointCount();
const Matrix mg = pointObject->GetMg();
for (Int32 i = 0; i < pointCount; ++i)
{
if (points)
{
const Vector point = points[i];
const Vector worldSpacePosition = mg * point;
if (sphere != nullptr)
{
sphere->SetMg(MatrixMove(worldSpacePosition));
doc->InsertObject(sphere, nullptr, nullptr);
}
}
}
Py_ssize_t i
Definition: abstract.h:645
maxon::Int32 Int32
Definition: ge_sys_math.h:60
#define Osphere
Sphere.
Definition: ge_prepass.h:1096
Matrix MatrixMove(const Vector &t)

## Edit Matrix

Basic operations to edit a matrix are done using operators or special functions:

// This example calculates the position of objectB in the local space of objectA.
const Matrix mgA = objectA->GetMg();
const Matrix inverse = ~mgA;
const Vector worldSpacePos = objectB->GetMg().off;
const Vector localSpacePos = inverse * worldSpacePos;
const maxon::String objectBName { objectB->GetName() };
const maxon::String objectAName { objectA->GetName() };
ApplicationOutput("Object "_s + objectBName);
ApplicationOutput("Position @ in the local space of @"_s, localSpacePos, objectAName);
Definition: string.h:1235

# Compare

Two matrices can be compared using the usual operators:

Note
For save comparison of floating point values see Compare.

# Disc I/O

Matrix objects can be stored in a BaseFile or a HyperFile using:

// This example writes the Matrix into a new BaseFile.
if (bf == nullptr)
return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
// open BaseFile to write
{
bf->WriteMatrix64(matrix);
bf->Close();
}
PyCompilerFlags const char * filename
Definition: ast.h:15
Definition: ge_autoptr.h:37
@ ANY
Show an error dialog for any error.
#define MAXON_SOURCE_LOCATION
Definition: memoryallocationbase.h:67
// This example reads a Matrix form the given BaseFile.
if (bf == nullptr)
return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
{
Matrix matrix;
// This example writes the Matrix into a new HyperFile.
if (hf == nullptr)
return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
// open HyperFile to write
if (hf->Open('matr', filename, FILEOPEN::WRITE, FILEDIALOG::ANY))
{
hf->WriteMatrix(matrix);
hf->Close();
}
// This example reads a Matrix from the given HyperFile.
if (hf == nullptr)
return maxon::OutOfMemoryError(MAXON_SOURCE_LOCATION);
{
Matrix matrix;

# Utility Functions

Several utility functions can be used to easily create matrices:

Matrices also represent rotations. Several functions can be used to change and obtain the rotation stored in a matrix:

Note

Matrix utility:

• RebuildMatrix(): Recalculates a matrix making it orthogonal if one or more of its vectors is collapsed
// This example creates a rotation matrix based on a direction vector
// and applies it to the given object.
const Vector vec { 100, 100, 100 };
const Vector rotation = VectorToHPB(vec);
const Matrix mg = HPBToMatrix(rotation, ROTATIONORDER::DEFAULT);
object->SetMg(mg);
@ DEFAULT
Default order (HPB).
Vector VectorToHPB(const Vector &p)
Matrix HPBToMatrix(const Vector &hpb, ROTATIONORDER rot_order)