**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, CONSECUTIVE OUTPUT FILE NUMBERS (Y/N): 26.0 , N

[Projections are only computed for the voxels inside the sphere of this radius. The output projections are normally numbered the same as the angles are numbered. If you wish to have multiple projections numbered consecutively starting with one, answer 'Y' to the second input value.].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 OUTPUT 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 often
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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