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Threshold T3D

Summary

The Threshold T3D turns a volume into a matte, like the Threshold TOP: the value chosen by RGB (luminance, one channel, or an average or maximum) is compared with Threshold, and voxels that satisfy Comparator become 0, the others 1. With Less, everything below the threshold drops out. Soften blends the step across a band around the threshold, which keeps the matte's edge smooth when it is rendered or used as a density.

Parameters - Threshold Page

Comparator Comparator ⊞ - The comparison between the value chosen by RGB and Threshold. As in the Threshold TOP, voxels that satisfy it become 0 and the others 1: with Less, values below the threshold are 0 (measured: 0.3 → 0, 0.7 → 1 at Threshold 0.5). Menu · default Less

  • Less less
  • Greater greater
  • Less or Equal lessorequal
  • Greater or Equal greaterorequal
  • Equal equal
  • Not Equal notequal

RGB Rgb ⊞ - The value compared: luminance (0.3 R + 0.6 G + 0.1 B), one channel, the average or the maximum of RGB or RGBA. Menu · default Luminance

Threshold Threshold - The value compared against. Float · default 0.5

Alpha Alpha ⊞ - Alpha of the output: the matte itself (Same as RGB), or 1 everywhere. Menu · default Same as RGB

  • Same as RGB same
  • One one

Soften Soften - Blends the matte across a band of this width around Threshold, instead of a hard step. With Equal and Not Equal it widens the match around the threshold. Float · default 0

Parameters - Common Page

Output Resolution Outputresolution ⊞ - Where the output's width, height and depth come from. With nothing connected to the first input the operator always uses Resolution, whichever option is set. Menu · default Use Input

  • Use Input useinput - The first input's width, height and depth.
  • Custom custom - The Resolution parameter.

Resolution Resolution1 Resolution2 Resolution3 ⊞ - Width, height and depth of the output in voxels. Used when Output Resolution is Custom, or when the first input is not connected. Memory is width × height × depth × bytes per voxel of the Pixel Format: 256³ at 16-bit float RGBA is 128 MiB. Int × 3 · default 64 · min 1

Input Smoothness Inputfiltertype ⊞ - Filtering of the internal GLSL TOPs' input samplers, as TouchDesigner's Input Smoothness. Inputs are read at normalised coordinates, so this matters whenever the input and output resolutions differ or an input is transformed. Nearest Pixel returns voxels unblended; Interpolate Pixels is trilinear. Menu · default Interpolate Pixels

  • Nearest Pixel nearest
  • Interpolate Pixels linear
  • Mipmap Pixels mipmap

Passes Npasses - Runs the operation this many times, each pass taking the previous pass's result in place of the first input. Cost scales linearly with the number of passes. Int · default 1

Pixel Format Format ⊞ - Pixel format of the output. Use Input takes the first input's format. With nothing connected, Use Input resolves to 8-bit fixed (RGBA), which clamps values to 0–1 and quantises them to 1/255: set a float format for signed distances, densities above 1, velocities or anything else outside 0–1. Menu · default Use Input

Bypass Bypass - Passes the first input through unchanged and skips the operator's work. With nothing connected the output is a single black voxel. Toggle · default Off

Version Version - T3D version of this operator. Read-only information; include it when reporting a problem. Str

Operator Inputs

  • Input 0: Input T3D_in1 - The volume to threshold.

Operator Outputs

  • Output 0: Output T3D_output - A matte, 0 or 1 (blended across Soften) in every channel.

Performance

GPU time when the operator recooks: 0.016 ms at 64³, 0.021 ms at 128³, all of its passes summed (GeForce RTX 4090, TouchDesigner 2025.33230). An operator whose inputs and parameters are unchanged does not recook and costs nothing.