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Matrix

Matrix math is widely used for various DCC to represent position, rotation and scale. Cinema4D provides a comprehensive introduction on its own implemention.

Gotchas​

  • For matrices, there is no such thing as division

Code Snippets​

# Retrieved from https://gist.github.com/andreberg/888507/f653bdb58299ca0efe198f4ff14525ca033c286a

def getGlobalPosition(obj):
    return obj.GetMg().off

def getGlobalRotation(obj):
    return MatrixToHPB(obj.GetMg()) # Use c4d.utils.RadtoDeg() to convert to degrees. 

def getGlobalScale(obj):
    m = obj.GetMg()
    return c4d.Vector(m.v1.GetLength(),
                        m.v2.GetLength(),
                        m.v3.GetLength())

@staticmethod
def setGlobalPosition(obj, pos):
    m = obj.GetMg()
    m.off = pos
    obj.SetMg(m)

@staticmethod
def setGlobalRotation(obj, rot):
    """
    Please remember, CINEMA 4D handles rotation in radians.
        
    Example for H=10, P=20, B=30:
        
    import c4d
    from c4d import utils
    #...
    hpb = c4d.Vector(utils.Rad(10), utils.Rad(20), utils.Rad(30))
    SetGlobalRotation(obj, hpb) #object's rotation is 10, 20, 30
    """
    m = obj.GetMg()
    pos = m.off
    scale = c4d.Vector( m.v1.GetLength(),
                        m.v2.GetLength(),
                        m.v3.GetLength())
                        
    m = HPBToMatrix(rot)
    
    m.off = pos
    m.v1 = m.v1.GetNormalized() * scale.x
    m.v2 = m.v2.GetNormalized() * scale.y
    m.v3 = m.v3.GetNormalized() * scale.z
    
    obj.SetMg(m)

@staticmethod
def setGlobalScale(obj, scale):
    m = obj.GetMg()
    
    m.v1 = m.v1.GetNormalized() * scale.x
    m.v2 = m.v2.GetNormalized() * scale.y
    m.v3 = m.v3.GetNormalized() * scale.z
    
    obj.SetMg(m)

def _GlobalToLocal(self, obj, global_pos) :
    """     Returns a point in global coordinate in local space. """    
    obj_mg = obj.GetMg()     
    return ~obj_mg * global_pos 


def get_points_global_matrix(obj, point_idx):
    
    obj_local_pos = obj.GetPoint(idx)
    obj_world_pos = obj.GetMg() * obj_local_pos