generative modeling for Rhino
but what i was looking for is not to use Grasshopper components
i mean is it possible by mathematics using these points x,x1,y,y1,z,z1,A to find B
lets say i like to do this in an excel file
You need to write the point in plane-coordinates. I.e. rewrite it from World-XYZ coordinates into Plane-UVW coordinates. Then, you can evaluate any other plane at the same UVW coordinates to get new XYZ coordinates and it will look as though the point has been moved along with the plane.
Using the Rhino SDK this is quite easy because all that functionality is already available, but it is just a large collection of multiplications, subtractions and divisions.
Another possibility (which only works for coordinates coincident with the plane defined by your three points) is to express the location as a weighted average. You could say for example that
A = (1.2*x0 + 1.5*y0 + 0.8*z0) / (1.2 + 1.5 + 0.8)
The benefit of this approach is that it requires significantly less mathematics.
but what is the relastionship between the avarage and the points coordinates
if x= (1,4,3) etc
where does the average came from
It think these are tri-linear coordinates.