**PURPOSE**- Computes projection(s) of a 3D volume according to three Eulerian angles. Uses non-uniform Fourier interpolation (gridding).

**SEE ALSO****PJ 3Q**[Project - 3D volume using Eulerian angles, trilinear interpolation ||] **PJ 3Q RR**[Project - 3D volume using Eulerian angles & create rings file ||] **RT SQ**[Rotate and Shift - image, Quadratic interpolation ||]

**USAGE**- .OPERATION: PJ 3G

- .INPUT VOLUME: vol001

[Enter the name of the volume whose projections are to be computed. This must be a cube.].ANGLE NUMBERS OR SELECTION DOC. FILE NAME: 1-700 or SEL001

[Enter selected angle numbers or name of a document file containing the selected angle numbers. Projections will only be calculated for the selected sets of angles from the following angles doc. file. (If you use a selection doc. file heer then the selected numbers are taken from the first register in the doc. file.)].ANGLES DOC. FILE: ANGLES

[Enter the name of the document file containing the Eulerian angles for the projections. The angles have to be given in the order: psi, theta, phi. The meaning of the angles is the same as in operation 'RT SQ'. Projections will be calculated for every entry specified in the previous question.].TEMPLATE FOR OUTPUT PROJECTIONS: PRJ****

[Enter the template for the output files which will contain the 2-D projections.]

**NOTES**

- The projection always has dimensions NX x NY.
- Reference: Penczek, P.A., Renka, R. and Schomberg, H.:
Gridding-based direct Fourier inversion of the
three-dimensional ray transform.
J. Opt. Soc. Am. A. 21:499-509, 2004.
- Psi, theta, & phi angles are placed in file header
starting at location: 100
- Implemented by: P.Penczek.

**SUBROUTINES**- PJ3G, WIW3G

**CALLER**- VTIL2

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