# Velocity vector as a quiver3d in ParaView

Hi,

I found a way to create a quiver3d representation of the velocity field in ParaView using the regular Gliph filter. I changed the Gliph Mode to Every Nth Point (and change the Stride) or all points. I used the 2d Gliph arrow.
I have a couple of questions:
1.Is there a way to use a custom image for the 2d gliphs?
2. I tried to take the quiver figure from Matlab, wrap it as a texture on the object and compare the results. They looked similar but not 100 percent the same.
Does someone have any idea why?

Misha

1.Is there a way to use a custom image for the 2d gliphs?

Yes, with a custom dataset, not a custom image. Use the GlyphWithCustomSource filter instead.

1. I tried to take the quiver figure from Matlab, wrap it as a texture on the object and compare the results. They looked similar but not 100 percent the same.

Can you share an image of the difference ?

It seems that the Gliph arrow generate arrows in the XYZ directions even though the data is in spherical coordinates. Is there a way to show the arrows in spherical coordinates?

You will have to convert your spherical coordinates verctors into cartesian coordinates first.

I tried using the following equation that was taken from:

U*(Rsin(Lat(3.14159265/ 180))cos(Lon(3.14159265/ 180))iHat+Rsin(Lat*(3.14159265/ 180))sin(Lon(3.14159265/ 180))jHat+Rcos(Lat*(3.14159265/ 180))kHat)+V(Rsin(Lat(3.14159265/ 180))cos(Lon(3.14159265/ 180))iHat+Rsin(Lat*(3.14159265/ 180))sin(Lon(3.14159265/ 180))jHat+Rcos(Lat*(3.14159265/ 180))*kHat)

(by the way, I am not sure why there is no Pi in the calculator, and if the units there are in radians or in degrees)

However, this didn’t produce good results with the Gliphs. Even when I checked the box “Coordinate Results”.

Misha

We indeed should have Pi in the calculator, @wascott opened an issue :
https://gitlab.kitware.com/paraview/paraview/issues/19210

Units are in radians, we could improve the doc, feel free to open an issue to improve it.
https://gitlab.kitware.com/paraview/paraview/issues

You should not check the box “Coordinate Results” as only your vector is in spherical coordinates, not your points.