Depth Slice is a simple gizmo to create a near, far, or centered slice with width and falloff controls.

DepthSlice.nk

set cut_paste_input [stack 0]
push $cut_paste_input
Group {
 name DepthSlice
 tile_color 0xcc804eff
 addUserKnob {20 DepthSlice}
 addUserKnob {41 depth t "Choose the depth channel to use for slicing." T CHAN_SEL.Zchan}
 addUserKnob {41 channel t "Channel to output depth." -STARTLINE T OUTPUT_LAYER.out}
 addUserKnob {26 "" +STARTLINE}
 addUserKnob {4 method t "choose the type of output: slice, near slice, or far slice." M {slice near far}}
 addUserKnob {41 slice_center T CalculateSlice.slice_center}
 addUserKnob {41 slice_width T CalculateSlice.slice_width}
 addUserKnob {41 feather T CalculateSlice.feather}
 addUserKnob {4 interpolation t "Choose the interpolation type for the feather." M {linear smooth0 smooth1 smooth cubic quadratic ""}}
}
 BackdropNode {
  inputs 0
  name BackdropNode1
  tile_color 0x4c4c4c01
  label "<left><font size=6><b>DepthSlice</b></font>\nblackpoint_OUT = 1/(1-blackpoint)*<INPUT>-1/(1-blackpoint)*blackpoint\nwhitepoint_OUT = 1/whitepoint*<INPUT>)\n\nFirst we get 1/depth near and far for specified center:\nnear = 1/(max((slice_center-a), 0)+1)\nfar = 1/(max((a-slice_center), 0)+1)\n\nThe we calculate a depth slice, and near slice and a far slice with the specified center, slice width, and feather.\n\nCenter is the distance from camera to center the slice. \nSlice width is the width in input units of the slice. \nFeather is what percentage of that width to feather off to the center. 1 = feather from center to center +/- slice_width / 2."
  note_font_size 24
  note_font_color 0x1e1e1eff
  xpos -1491
  ypos -880
  bdwidth 1226
  bdheight 759
 }
 ZBlur {
  inputs 0
  channels rgba
  shape 1
  name CHAN_SEL
  xpos -1380
  ypos -690
 }
 Input {
  inputs 0
  name Input
  xpos -442
  ypos -930
 }
 AddChannels {
  channels rgba
  channels2 depth
  name AddChannels1
  xpos -442
  ypos -850
 }
 Dot {
  name Dot1
  label " "
  note_font "Helvetica Bold Bold"
  note_font_size 24
  note_font_color 1
  xpos -408
  ypos -726
 }
set Naab2a90 [stack 0]
 Dot {
  name Dot2
  label " "
  note_font "Helvetica Bold Bold"
  note_font_size 24
  note_font_color 1
  xpos -1212
  ypos -726
 }
set N32d42210 [stack 0]
push $N32d42210
 Copy {
  inputs 2
  from0 {{{CHAN_SEL.Zchan}}}
  to0 rgba.alpha
  name COPY_DEPTH
  xpos -1246
  ypos -697
 }
 Expression {
  temp_name0 near
  temp_expr0 "1/(max((slice_center-a), 0)+1)"
  temp_name1 far
  temp_expr1 "1/(max((a-slice_center), 0)+1)"
  expr0 "clamp(1/feather*((1-1/min(near, far)/(slice_width+1))))"
  expr1 clamp(1/feather*((1-1/far/(slice_width+1))))
  expr2 clamp(1/feather*((1-1/near/(slice_width+1))))
  channel3 none
  name CalculateSlice
  xpos -1246
  ypos -641
  addUserKnob {20 Params}
  addUserKnob {7 slice_center t "The Center to take the depth slice from" R 1 500}
  slice_center 100
  addUserKnob {7 slice_width t "The slice width - falloff is extra" R 1 100}
  slice_width 25
  addUserKnob {7 feather t "The amount of falloff"}
  feather 1
 }
 Expression {
  channel0 rgba
  expr0 "parent.method == 2 ? b : parent.method == 1 ? g : r"
  name OUTPUT_TYPE
  xpos -1246
  ypos -599
  addUserKnob {20 User}
  addUserKnob {7 output_method}
 }
 Dot {
  name Dot8
  label " "
  note_font "Helvetica Bold Bold Bold Bold"
  note_font_size 24
  note_font_color 0xff000000
  xpos -1212
  ypos -526
 }
set N36531250 [stack 0]
 Expression {
  channel3 rgba
  expr3 clamp((a**3),0,1)
  name Cubic
  xpos -576
  ypos -490
 }
push $N36531250
 Expression {
  channel3 rgba
  expr3 clamp(pow2(a),0,1)
  name Quadratic
  xpos -710
  ypos -490
 }
push $N36531250
 Expression {
  channel3 rgba
  expr3 smoothstep(0,1,a)
  name Smooth
  xpos -844
  ypos -490
 }
push $N36531250
 ColorLookup {
  lut {master {curve C 0 k 1 s0}
    red {}
    green {}
    blue {}
    alpha {}}
  name Smooth1_
  xpos -978
  ypos -490
 }
push $N36531250
 ColorLookup {
  lut {master {curve C k 0 s0 L 1}
    red {}
    green {}
    blue {}
    alpha {}}
  name Smooth0_1
  xpos -1112
  ypos -490
 }
push $N36531250
 Switch {
  inputs 6
  which {{parent.interpolation}}
  name _INTERPOLATION_
  xpos -1246
  ypos -370
 }
 Dot {
  name Dot3
  label " "
  note_font "Helvetica Bold Bold"
  note_font_size 24
  note_font_color 1
  xpos -1212
  ypos -246
 }
push $Naab2a90
 ShuffleCopy {
  inputs 2
  red red
  green green
  blue blue
  out alpha
  name OUTPUT_LAYER
  xpos -442
  ypos -250
 }
 Output {
  name Output
  xpos -442
  ypos -90
 }
end_group

Depth Slice is a very simple and fast gizmo that creates a slice from a depth channel. It has 3 modes of operation.

• Slice mode creates a slice in depth centered at the specified depth. You can adjust slice width and feather.
• Near mode creates a slice in depth from the camera to the specified center, with a feather adjustment.
• Far mode creates a slice in depth from the slice center to infinity, with a feather adjustment.