I found the solution (I already had this problem but I couldn't remember the right code)

mat [c4d.MATERIAL_TRANSPARENCY_COLOR] = c4d.Vector (1.0, 1.0, 1.0) #color white
mat.Update (True, True)

I found the solution to my problem, on the internet, with code samples:
https://www.c4dcafe.com/ipb/forums/topic/101805-materials-and-shaders-with-python/

The following example illustrates my problem.
In this example, I translate and rotate the ring using C4D's interface.

In figure 1, the ring is at point (0,0,0) with an angle of zero.
Figure 1

In figure 2, using the Cinema 4D interface, I translate the ring with the vector <2,1,3> in centimeters.
Then I performed three successive rotations: 322° on the X axis, 30° on the Y axis and 343° on the Z axis.
Cinema 4D positioned the axis center of the ring correctly.
Figure 1

But when I create my ring with 4 splines, at a point in space other than (0,0,0), the axis center always remains at the point (0,0,0) with an angle of zero.
I'd like the axis center to be at the center of my ring and at the same angle as in Cinema 4D.

Let me explain.
My problem may be complicated to understand, but my final request is very simple.
In C4D, I've got into the habit of creating my 3D objects with splines, which allows me to create objects of any kind.
I do this with Python.
So to create a ring, I create 4 splines. Then, with these 4 splines, I create the ring.

If my 4 splines are centered on the point (0,0,0) as shown in the image below, my ring lies on the XZ plane.
The axis center of the ring is also on the point (0,0,0). What's more, it's well oriented, as its Y axis corresponds to the Y axis of my ring.
Furthermore, the X axis of the axis center is aligned with the segments connecting the point (0,0,0) with the first points of my construction splines.
In this case, everything is perfect.
Figure 1

However, if the center of my 4 splines is elsewhere and the orientation is arbitrary, as shown in the image below, this is where the problem arises.
After creating my ring, the axis center remains at the point (0,0,0) and its orientation is identical to the previous case.
Figure 2

So I need to use Python to bring the axis center back to the center of my ring (translation).
Next, I need to rotate the axis center so that its Y axis is perpendicular to the plane of my ring.
Next, I need to rotate the axis center around its Y axis, so that its X axis is parallel to the segments connecting the center of the ring with the first points of my construction splines.

In conclusion:
I need the following functions:

• a function that allows the translation of the axis center, from a point A to a point B
• a function that allows the rotation of the axis center around its X axis
• a function that allows the rotation of the axis center around its Y axis
• a function that allows the rotation of the axis center around its Z axis

Hi,

With python, I generate a ring in space that is far from the center (0,0,0)

The ring is in the plane formed by two vectors u and v.

The vector w is perpendicular to the ring.

After creating the ring, its center axis is at the position (0,0,0)

I would like to place the center axis at the center of the ring whose position I know.
In addition, I would like the axes of the center axis to correspond to the base (u,v,w) in which I created the ring.

@ferdinand

I made this function which works fine:

def spline_update(doc,spline,tabNewPoint):
	tabPoint = spline.GetAllPoints()
	
	dim = len(tabNewPoint)
	if len(tabPoint) != dim:
		spline.ResizeObject(dim)
	
	for i in range(0,dim):
		point = tabNewPoint[i]
		spline.SetPoint(i,point)

	spline.Message(c4d.MSG_UPDATE)
	return spline

Hi

How to update a spline if the number of points changes ?

If the number of points is the same, we can use the following function:

def spline_update(spline,tabPoint):
	dim = len(tabPoint)
	for i in range(0,dim):
		spline.SetPoint(i,tabPoint[i])

	spline.Message(c4d.MSG_UPDATE)
	return spline

If the number of points changes, we must use the ResizeObject() method

I'm looking for an example, which will save me from doing tests.

I found the solution on https://plugincafe.maxon.net/
It was enough in the for loop to add the following line of code:

for object in list_object:
if object != object_root:
object.InsertUnder(object_root)
c4d.EventAdd()

Hi,

With a script, I create a large number of objects in my scene.
In the hierarchy, they are presented in the form of a list, which becomes difficult to read because it's too long.
So I want to put the names of the child objects under the name of the root object.
How can I do this ?

def hierarchie_organise(doc, object_root, list_object):
	# document name: doc
	# object root: object_root
	# child objects: list_object 

	# checking (exclusion of the root object if it's in the list of child objects)
	list_child = []
	for object in list_object:
		if object != object_root:
			list_child.append(object)

	# positioning of list_child objects under the object_root object
	...
	...
	...

	return 

True

I have created a function that adds points to a polygon.
But how to remove a point from a polygon, as well as remove the faces that contain it ?

Creation of UVW tag for a plane
I would like to know how to create texture coordinates for a plane, with python.
So I want to create with python the basic UVW tag for a plan.
I would like to get the same result as with Bodypaint.

@ferdinand

Thanks, it works well

My first method was complex:

• creation of a new orthogonal spatial system, with one of its axes is identical to the axis of rotation
• compute the coordinates of the points of the object in this new spatial system, then rotate the object
• calculation of the new coordinates in the initial orthogonal spatial system.