The following simulation show two point source located at P1=(x1,y1,z) and P2=(x2,y1,z)
It only show waves moving toward a common point P=(x,y,z), so that the interference can be shown at (x,y,z)
where r1 is the distance of bwtween P1 and P.
where r2 is the distance of bwtween P2 and P.
You can change the distance between source with slider for d, location of observed point with slider for x,wavelength with slider for lambda.
Two blue arrows represent phases for those two wave at P. i.e. represent (k*r1-w*t and k*r2-w*t).