Here is an example input file for hvr_cl

Anot:       0 0.000000
Anot:      95 0.000000
Anot:     114 0.407843
Anot:     255 1.000000
Cnot:       0 0.000000 0.000000 0.000000
Cnot:      77 0.000000 0.000000 0.000000
Cnot:     128 1.000000 0.000000 0.000000
Cnot:     192 1.000000 1.000000 0.000000
Cnot:     255 1.000000 1.000000 1.000000
opacity         1.000000
hvfile          test.hv
imagesize       1280, 1024
imagefile       RHO_full_angle.raw
fov             35.308399
eye             -3.512593, 0.150125, -2.480027
center          0.000000, 0.150125, 0.000000
up              0.000000, 1.000000, 0.000000
clipping        0.429987, 14.299866
nplanes         1.000000, 1.000000
softdistance    0.000000
tolerance       0 0.0002 1.000000
timer
render
timer

These files are organized in a keyword-value format.
  Keywords are the first string in each line
  Value(s) are in the remainder of the line.
  Keywords and values (if needed by a keyword) are space or comma 
delimited.


Keyword-Value Synopses:

-------------------------------------------------------------------------------
Anot:   INDEX  ALPHA
 INDEX = index of alpha map tie point (alpha-knot).
 ALPHA = Opacity (or alpha) value associated with <INDEX>
These lines specify a map between the singe-byte voxel fields
and an alpha (i.e., opacity) value used in alpha-blending.
ALPHA = 0.0 implies that the voxel is transparent.
ALPHA = 1.0 implies that the voxel is opaque.
Valid ranges:
 INDEX    [0, 255]
 ALPHA    [0.0, 1.0]
Other constraints
1) There need to be at least two alpha "knots" specified,
one at INDEX 0, and one at INDEX 255.
2) INDEXs should be monotone increasing in the file

-------------------------------------------------------------------------------
Cnot:   INDEX  RED  GREEN  BLUE
 INDEX = index of color map tie point (color-knot).
 RED   = red color value associated with <INDEX>
 GREEN = green color value associated with <INDEX>
 BLUE  = blue color value associated with <INDEX>
These lines specify a map between the singe-byte voxel fields
and an RGB color value used in alpha-blending.
RED, GREEN, or BLUE = 0.0 implies zero intensity for that color channel.
RED, GREEN, or BLUE = 1.0 implies maximum intensity for that color channel.
Valid ranges:
 INDEX                  [0, 255]
 RED, GREEN, or BLUE    [0.0, 1.0]
Other constraints
1) There need to be at least two color "knots" specified,
one at INDEX 0, and one at INDEX 255.
2) INDEXs should be monotone increasing in the file

-------------------------------------------------------------------------------
opacity    OPACITY_SCALING
 OPACITY_SCALING = global scaling of opacities
This parameter linearly scales the alphas used in alpha-blending to increase
or decrease the effective optical depth of the data.  If OPACITY_SCALING=1.0
and all voxels are mapped to full maximum alpha (1.0), then one unit of
distance (in the users model view space) will have an optical depth of 
unity.
Valid range:  a positive 32-bit floating point number

-------------------------------------------------------------------------------
hvfile    FILE_NAME
 FILE_NAME = name of disk file containing block-tree formatted volume data
This file name can be local to the current working directory (test.hv),
a relative path (../otherdir/test.hv), or a full path (/mnt/data/test.hv).

-------------------------------------------------------------------------------
imagesize   NX  NY
 NX = Horizontal image pixel resolution
 NY = Vertical image pixel resolution
Valid ranges: limited by size of X-window

-------------------------------------------------------------------------------
imagefile   FILE_NAME
 FILE_NAME = name of image file produced
A full, relative or local path may be used here.

-------------------------------------------------------------------------------
fov       ANGLE
 ANGLE = vertical field of view opening angle of rendering frustum.
Images are rendered in perspective geometry.  ANGLE specifies the full
vertical penning angle (in degrees).  Larger opening angles imply stronger
perspective.  The ratio of horizontal to vertical opening angles
is determined by the ratio of horizontal to vertical pixels of the image
size: pixels are assumed to be square.
Valid range: (0.0, 180)
  Values large than 60 give you a "fish-eye" view.
  You see behind your head with values larger than 90 .

-------------------------------------------------------------------------------
eye      X Y Z
(X,Y,Z) = Cartesian coordinates of view point in model view space.
Valid Range: 3 floating point numbers.

The size and location of the volume data in "model view" coordinates
are specified as XYZ limits of a bounding box, which are usually included
included in the HV file (specified in the hvfile line).  This bounding box
is determined when the HV file is created, and should reflect units of size
relevant to the user's data.

-------------------------------------------------------------------------------
center   X Y Z
(X,Y,Z) = Cartesian coordinates of "look-at" point in model view space.
Valid Range: 3 floating point numbers.

-------------------------------------------------------------------------------
up       X Y Z
(X,Y,Z) = components of  "up-vector" in model view space.
Valid Range: 3 floating point numbers.

-------------------------------------------------------------------------------
clipping    NEAR  FAR
 NEAR = distance to near clipping plane from the eye point in model view space.
 FAR  = distance to far clipping plane from the eye point in model view space.
Valid range: two floating point numbers, with: 0.0 < NEAR < FAR.

-------------------------------------------------------------------------------
nplanes    N_PANES_PER_VOXEL   MAX_PANES_PER_VOXEL
 N_PANES_PER_VOXEL = number of rendering planes used per voxel layer
 MAX_PANES_PER_VOXEL = maximum number of rendering planes used per voxel layer
Increasing N_PANES_PER_VOXEL (from 1) will sometimes reduce rendering artifacts,
but increase rending time.  Most useful when zoomed in and the point when
individual rendering planes can be seen.
MAX_PANES_PER_VOXEL is currently implemented., and should = N_PANES_PER_VOXEL
valid ranges:  two positive integers

-------------------------------------------------------------------------------
softdistance    DISTANCE
 DISTANCE = thickness of near and far clipping planes.
Not currently implemented.  This line is ignored and can be omitted.

-------------------------------------------------------------------------------
tolerance     VALUE_TOLERANCE  ANGLE_TOLERANCE  SIZE_TOLERANCE
 VALUE_TOLERANCE = acceptable value error.
 ANGLE_TOLERANCE = acceptable angle error.
 SIZE_TOLERANCE  = acceptable voxel size.
These three parameters are used to control the trade off between quality and
speed of rendering by limiting how deeply hvr digs into block-tree data.
Starting with the root block of the tree, hvr asks if this block is
"good enough" for the current rendering: if yes, then this block is use
and none of the sub-blocks (within it) are used; if no, then the
hierarchical tree scan continues to the next level of refinement
within this block.  A block is considered "good enough" is any of three
conditions (based on value, angle, and voxel size) are satisfied.
Valid ranges and explanations:
 VALUE_TOLERANCE  [0, 255]  limits  the maximum index value error incurred
by using a given block.  A value of 0 will allow high quality renderings
(depending on the other two tolerances).  Note if the data is constant on
the finest level everywhere in the spatial domain of the block, then lower
resolution blocks will still be used.
 ANGLE_TOLERANCE (a positive floating point number) limits the maximum
angular size in Radians (subtended by the eye point) of any voxel in the 
block.
Large values of ANGLE_TOLERANCE (like 0.02) will force fast but poor quality
renderings.  Very small values allow high quality renderings (depending on
the other tolerances).  Optimal values of ANGLE_TOLERANCE are near the
angle subtended by an individual pixel, which is determined by the vertical
field of view (see keyword: fov) and image size (see keyword: imagesize).
 SIZE_TOLERANCE (a floating point number >= 1.0) limits the voxel size
relative to the finest level of refinement.  A value of 8.0 or more for 
always
produce very quick (interactive speed) and usually poor quality renderings.
A value of 1.0 allows full quality, depending on the other tolerances.

-------------------------------------------------------------------------------
render
 (no arguments)
Causes hvr to produce an image with the settings specified in the file 
so far.
Multiple rendering can be specified in a single file.  For example, two
renderings from different point of view can be specified by
...
center   0.0  0.0  0.0
eye       1.0  0.0  0.0
up        0.0  0.0  1.0
imagefile  view100.raw
render
eye       0.0  1.0  0.0
imagefile  view010.raw
render

-------------------------------------------------------------------------------
timer
 (no arguments)
Reports timings  and rendering speeds.  The 1st occurrenceof timer generates
a report of the current clock time on the host.  Subsequent occurrences of
timer generate reports of clock time and the time (in seconds) since the 
last
occurrenceof timer.  for example,
...
timer
render
timer

will give you the time to render the image.