**PURPOSE**- Computes projection(s) of a cubic volume according to three Eulerian angles. Reads angles from a document file. Uses trilinear interpolation. Example.

**SEE ALSO****PJ 3F**[Project - 3D volume using Eulerian angles, FBS interpolation ||] **PJ 3Q RR**[Project - 3D volume using Eulerian angles & create rings file ||] **PJ 3**[Project - 3D volume using Eulerian angles, trilinear or FBS interpolation, single projection] **PJ AT**[Project - 3D volume using exponential Attenuation] **PJ CYL**[Project - 3D volume onto Cylinder] **RT SQ**[Rotate and Shift - image, Quadratic interpolation ||]

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

- .INPUT VOLUME: vol001

[Enter the name of the volume whose projections are to be computed.].OBJECT RADIUS: 26.0

[The projections are only computed for the voxels inside the sphere of this radius.].ANGLE NUMBERS OR SELECTION DOC. FILE NAME: 1-700 or SEL001

[**Note nonstandard order here**, number of angles preceeds angle file name. 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 here then the selected numbers are taken from the first register (3rd col) 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. Projections will be calculated for every entry specified in the previous question. The projection is made as if the volume was rotated by the psi angle around the Z axis, followed by the theta angle around the original Y axis and then rotated by the Phi angle around the original Z axis.].TEMPLATE FOR 2-D PROJECTIONS: PRJ****

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

**NOTES**

- For a projection of the whole volume (not the internal
sphere only) give a radius larger than any linear
dimension of the volume. Please note that usually
such a projection is incorrect and the program takes
much longer.
- Since values are interpolated, projection through a
volume containing a single point may give an image
in which the max exceeds the original value. This is not a bug.
- Implemented by: P. Penczek.
- Psi, theta, & phi angles are placed in file header starting at location: 100

**SUBROUTINES**- PJ3Q_N, PREPCUB, WRITPRO_N, WPRO_N

**CALLER**- VTIL2

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