You move, scale, or rotate an object given a 4 by 4 transformation matrix using the TransformBy method.
The following table demonstrates the transformation matrix configuration, where R = Rotation and T = Translation:
|
Transformation matrix configuration | |||
|---|---|---|---|
|
R00 |
R01 |
R02 |
T0 |
|
R10 |
R11 |
R12 |
T1 |
|
R20 |
R21 |
R22 |
T2 |
|
0 |
0 |
0 |
1 |
To transform an object, first initialize the transformation matrix. The following example shows a transformation matrix, assigned to the variable tMatrix, which will rotate an entity by 90 degrees about the point (0, 0, 0):
tMatrix(0,0) = 0.0
tMatrix(0,1) = -1.0
tMatrix(0,2) = 0.0
tMatrix(0,3) = 0.0
tMatrix(1,0) = 1.0
tMatrix(1,1) = 0.0
tMatrix(1,2) = 0.0
tMatrix(1,3) = 0.0
tMatrix(2,0) = 0.0
tMatrix(2,1) = 0.0
tMatrix(2,2) = 1.0
tMatrix(2,3) = 0.0
tMatrix(3,0) = 0.0
tMatrix(3,1) = 0.0
tMatrix(3,2) = 0.0
tMatrix(3,3) = 1.0
After the transformation matrix is complete, apply the matrix to the object using the TransformBy method. The following line of code demonstrates applying a matrix (tMatrix) to an object (anObj):
anObj.TransformBy tMatrix
Rotate a line with a transformation matrix
This example creates a line and rotates it 90 degrees using a transformation matrix.
Sub Ch4_TransformBy()
' Create a line
Dim lineObj As AcadLine
Dim startPt(0 To 2) As Double
Dim endPt(0 To 2) As Double
startPt(0) = 2
startPt(1) = 1
startPt(2) = 0
endPt(0) = 5
endPt(1) = 1
endPt(2) = 0
Set lineObj = ThisDrawing.ModelSpace. _
AddLine(startPt, endPt)
ZoomAll
' Initialize the transMat variable with a
' transformation matrix that will rotate
' an object by 90 degrees about the point(0,0,0)
Dim transMat(0 To 3, 0 To 3) As Double
transMat(0, 0) = 0#: transMat(0, 1) = -1#
transMat(0, 2) = 0#: transMat(0, 3) = 0#
transMat(1, 0) = 1#: transMat(1, 1) = 0#
transMat(1, 2) = 0#: transMat(1, 3) = 0#
transMat(2, 0) = 0#: transMat(2, 1) = 0#
transMat(2, 2) = 1#: transMat(2, 3) = 0#
transMat(3, 0) = 0#: transMat(3, 1) = 0#
transMat(3, 2) = 0#: transMat(3, 3) = 1#
' Transform the line using the defined transformation matrix
lineObj.TransformBy transMat
lineObj.Update
End Sub
The following are more examples of transformation matrices:
|
Rotation Matrix: 90 degrees about point (0, 0, 0) | |||
|---|---|---|---|
|
0.0 |
-1.0 |
0.0 |
0.0 |
|
1.0 |
0.0 |
0.0 |
0.0 |
|
0.0 |
0.0 |
1.0 |
0.0 |
|
0.0 |
0.0 |
0.0 |
1.0 |
|
Rotation Matrix: 45 degrees about point (5, 5, 0) | |||
|---|---|---|---|
|
0.707107 |
-0.707107 |
0.0 |
5.0 |
|
0.707107 |
0.707107 |
0.0 |
-2.071068 |
|
0.0 |
0.0 |
1.0 |
0.0 |
|
0.0 |
0.0 |
0.0 |
1.0 |
|
Translation Matrix: move an entity by (10, 10, 0) | |||
|---|---|---|---|
|
1.0 |
0.0 |
0.0 |
10.0 |
|
0.0 |
1.0 |
0.0 |
10.0 |
|
0.0 |
0.0 |
1.0 |
0.0 |
|
0.0 |
0.0 |
0.0 |
1.0 |
|
Scaling Matrix: scale by 10,10 at point (0, 0, 0) | |||
|---|---|---|---|
|
10.0 |
0.0 |
0.0 |
0.0 |
|
0.0 |
10.0 |
0.0 |
0.0 |
|
0.0 |
0.0 |
10.0 |
0.0 |
|
0.0 |
0.0 |
0.0 |
1.0 |
|
Scaling Matrix: scale by 10,10 at point (2, 2, 0) | |||
|---|---|---|---|
|
10.0 |
0.0 |
0.0 |
-18.0 |
|
0.0 |
10.0 |
0.0 |
-18.0 |
|
0.0 |
0.0 |
10.0 |
0.0 |
|
0.0 |
0.0 |
0.0 |
1.0 |