HLT3D plots a 2 dimensional array to produce a 2-d histogram similar to PLT3D. Hidden lines are supressed. Transformation from the array indices (i,j) to (x,y,z) is:
x = xl * .5 * float(2*j-n-1)/float(n-1)
y = yl * .5 * float(2*i-m-1)/float(m-1)
z = zs * (a(i,j) + z0)
Thus,
(1,1) is (-xl/2,-yl/2) (m,1) is (-xl/2,+yl/2)
(1,n) is (+xl/2,-yl/2) (m,n) is (+xl/2,+yl/2)
xplotted = x*cos(az) - y*sin(az) + x0
yplotted = x*sin(az)*sin(al) + y*sin(az)*sin(al) + z*cos(al) + y0
The common block PLT3B returns these transformation parameters so that the plotted location (xp,yp) of the corner of the cube corresponding to the point (i,j,zr) may be computed as:
xp = a1 * j + a2 * i + a3
yp = b1 * j + b2 * i + b3 * zr + b4
The dimension of the working array is dependent on the surface complexity -- the greater the surface complexity, the greater l2 must be. As a minimum, l2 > 4*min(m,n). See also NXTVU and PLT3D.
CALL HLT3D (a,md,nd,m,n,w,l,w2,l2,al,az,xl,x0,yl,y0,zs,z0,ierr)
a (R): array of values to be plotted dimensioned a(md,nd)
md,nd (I): array dimensions
m,n (I): size of data in array to be plotted
w (R): dummy variable so that call is compatible with PLT3D
l (I): dummy variable so that call is compatible with PLT3D
w2 (R): working storage array dimensioned w2(l2)
l2 (I): working storage array dimension (see note)
al (R): viewing altitude angle (deg)
az (R): viewing azimuth angle (deg)
xl,yl (R): length of unprojected axes in plot units
x0,y0 (R): plot origin in plot units
zs (R): z coordinate scale factor
z0 (R): z coordinate offset
ierr (I): (returned) error code
= 0 : ok
= 1 : l2 not large enough in NXTVU
COMMON /PLT3B/ a1,a2,a3,b1,b2,b3,b4