**PURPOSE**- Computes a projection of a 3D density distribution onto a cylinder surrounding the volume. The axis of the cylinder is assumed to be the Y axis. The origin is specified for each plane perpendicular to Y using a document file that contains the X,Z coordinates of the projection centers (intended for curved fibers). The cylinder is then unrolled into a 2D image. Example.

**SEE ALSO****PJ 3**[Project - 3D volume using Eulerian angles, trilinear or FBS interpolation, single projection] **PJ 3Q**[Project - 3D volume using Eulerian angles, trilinear interpolation ||] **PJ AT**[Project - 3D volume using exponential Attenuation]

**USAGE**- .OPERATION: PJ CYL

- .THREED FILE: PIC001

[Enter the name of the file whose projection is to be computed. Should be a cube!].OUTPUT FILE: CYL001

[Enter name for the output file].STARTING ANGLE: 90

[Enter starting angle. Zero is at 3 o'clock on cylinder.].INNER, OUTER RADIUS: 5, 32

[Enter inner and outer radius of cylinder. From the outer radius the X-dimension of the output image is calculated as YDIM=Radius*2*PI, and the angular increment as 360/YDIM. If inner radius < 0, the program does a maximum projection instead of regular summation. If outer radius < 0, the program finds the distance of the last positive pixel along the radius from the center of the projection.]

The program prints out: ANGULAR INCREMENT: 3.75 DEGREES, X DIMENSION: 91

.NEW INCREMENT OR <RET>: 4.5

[Enter a new angular increment if you want to overwrite the one calculated. The file dimensions are automatically adjusted.].COLUMNS FOR X-CENTER, Z-CENTER: 1,2

[Enter the column numbers for the center coordinates in the document file.].DOCUMENT FILE: DOC001

[Enter the document file that contains the projection centers.]

**SUBROUTINES**- MRCP

**CALLER**- VTIL2

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