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Surface T3D

Summary

The Surface T3D renders a volume as a solid: the surface where the density's Channel crosses Threshold, found by ray-marching inside a box with the volume's proportions. Its normals come from the density's gradient, measured over Normal Smoothing voxels, and it is shaded like TouchDesigner's Constant, PBR or Phong MAT by the Render TOP's lights.

A second input colours the surface, and Use Maps adds 3D textures that vary the material's parameters across it. With Refraction Steps above 0 the surface becomes transparent: rays bend into the shape and out again, tinted by Occlusion Color on the way, and show an environment map or a backdrop image behind. Extra colour buffers can carry positions and normals for compositing.

Use it with sdf, metaball, geo_to or any density; a T3D Transform Reference puts the surface where the volume's source geometry was.

Parameters - Surface Page

Threshold Threshold - The iso-value: the surface is where the density's Channel crosses it. Lower values give a larger shape. Float · default 0.5

Channel Channel ⊞ - The value of the density the surface is taken from. Menu · default Red

Normal Smoothing Normalsmoothing - Distance, in voxels, over which the normal is measured. 1 follows the voxels closely; larger values smooth faceting and small bumps out of the shading. Float · default 1 · min 0.05

Panel COMP Refpanel - The panel of the operator's built-in camera viewer. Leave at its default. PanelCOMP · default ./cameraViewport/renderView

Render TOP Refrender - The Render TOP of the operator's built-in camera viewer. Leave at its default. TOP · default ./cameraViewport/renderView/render1

T3D Transform Reference Transformreference - An operator that exports the mapping between the volume and world space (geo_to, point_cloud, metaball, sprinkle, advect): the surface is drawn where that operator's source was. COMP

Parameters - Material Page

Type Type ⊞ - The shading model, as TouchDesigner's Constant, PBR and Phong MATs, lit by the Render TOP's lights. Menu · default Phong

  • Constant Constant
  • PBR PBR
  • Phong Phong

Constant Constant - Settings of the Constant model. Header

Color Colorr Colorg Colorb ⊞ - The surface's colour, unlit. RGBA × 3 · default 1

PBR Pbr - Settings of the PBR model. Header

Base Color Basecolorr Basecolorg Basecolorb ⊞ - Base colour, as the PBR MAT. RGBA × 3 · default 1

Specular Level Specularlevel - Strength of the specular reflection of non-metals, as the PBR MAT. Float · default 1 · min 0

Metallic Metallic - 0 dielectric, 1 metal, as the PBR MAT. Float · default 1 · min 0

Roughness Roughness - 0 mirror-like, 1 fully rough, as the PBR MAT. Float · default 1 · min 0

Ambient Occlusion Ambientocclusion - Multiplies the ambient and environment light. Float · default 1 · min 0

Phong Phong - Settings of the Phong model. Header

Ambient uses Diffuse Ambdiff - Uses the Diffuse colour for ambient light too. Toggle · default On

Diffuse Diffr Diffg Diffb ⊞ - Diffuse colour. RGBA × 3 · default 0.7

Ambient Ambr Ambg Ambb ⊞ - Ambient colour, when Ambient uses Diffuse is off. RGBA × 3 · default 0.7

Specular Specr Specg Specb ⊞ - Specular colour. RGBA × 3 · default 0.3

Emit Emitr Emitg Emitb ⊞ - Emitted colour, added regardless of lighting. RGBA × 3 · default 0

Constant Constant2r Constant2g Constant2b ⊞ - A constant colour added on top. RGBA × 3 · default 0

Shininess Shininess - Tightness of the specular highlight. Float · default 100 · min 1

Parameters - Refraction Page

Refraction Steps Refractionsteps - How many times a view ray may pass through the surface. 0 renders it opaque; above 0 the ray refracts into the shape and out again, up to this many crossings, and shows what lies behind. Int · default 0

Translucency Translucency - How much of the refracted light shows through, against the shaded surface. Float · default 0.25

Refraction Index Refractionindex - Index of refraction of the inside (1 no bending, 1.33 water, 1.5 glass). Float · default 1 · min 0.001

Fresnel Fresnel - Reflects more at grazing angles, as real transparent surfaces do. Toggle · default On

Occlusion Strength Occlusionstrength - Absorption inside the shape: refracted light is tinted towards Occlusion Color with the distance travelled. Float · default 0

Use Color Map Usecolormap - Uses the Color input as the absorption colour inside the shape. Toggle · default Off

Occlusion Color Occlusioncolorr Occlusioncolorg Occlusioncolorb ⊞ - The colour light takes on inside the shape. RGBA × 3 · default 0

Background Background - What refracted rays see behind the shape. Header

Mode Bgmode ⊞ - An environment map around the scene, or a backdrop image on a plane behind the shape. Menu · default Environmental Map

  • Environmental Map EnvironmentalMap
  • Backdrop Backdrop

Environment Map Environmentmap - The environment image (latitude-longitude) seen through the shape. TOP

Environment Map Rotate Envlightmaprotatex Envlightmaprotatey Envlightmaprotatez ⊞ - Rotation of the environment map, in degrees about X, Y and Z. Float × 3 · default 0

Backdrop Backdrop - The image on the backdrop plane. TOP

Backdrop Distance Backdropdistance - Distance of the backdrop plane behind the shape, in world units. Float · default 5

Backdrop Prefit Backdropprefit ⊞ - How the backdrop image fits its plane. Menu · default Fill

  • Fill fill
  • Fit Horizontal fithorz
  • Fit Vertical fitvert
  • Fit Best fitbest
  • Fit Outside fitoutside
  • Native Resolution nativeres

Backdrop Pre-Shrink Preshrink - Pre-shrink of the blur applied to the backdrop (a softer backdrop for rough refraction). Int · default 1 · min 1

Backdrop Filter Size Size - Filter size of the blur applied to the backdrop. Int · default 7 · min 1

Backdrop Extend Backdropextend ⊞ - What the backdrop returns beyond its edges. Menu · default Repeat

  • Hold hold
  • Zero zero
  • Repeat repeat
  • Mirror mirror

Render Background Renderbackground - Draws the environment or backdrop itself behind the shape, so the refraction matches what is visible. Toggle · default Off

Parameters - Maps Page

Use Maps Usemaps - Adds four material-map inputs, 3D textures sampled at the surface: for Phong, diffuse, specular, emission and shininess; for PBR, specular level, metallic, roughness and ambient occlusion. Toggle · default Off

Mode Mode ⊞ - Multiply multiplies the material parameters by the maps; Set uses the maps' values instead. Menu · default Multiply

  • Multiply Multiply
  • Set Set

Parameters - Buffers Page

Color Buffer Colorbuffer - Extra colour buffers of the Render TOP, one block each (set the Render TOP's number of colour buffers to match): what the surface writes into them. Sequence · default 0

RGB Colorbuffer0rgb ⊞ - The content of this buffer: the full shading, the position (world, T3D UVW or camera space), or the normal (world, T3D or camera space). For compositing, relighting or post effects. Menu · default Full Shading

  • Full Shading Full
  • World Space Position World
  • T3D UVW UVW
  • Camera Space Position CameraPos
  • World Space Normal Normal
  • T3D Normal T3DNormal
  • Camera Space Normal CameraNormal

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

Operator Inputs

  • Input 0: Density density - The volume whose isosurface is rendered: the surface lies where Channel crosses Threshold.
  • Input 1: Color color - Optional. A 3D texture that colours the surface where it passes through, multiplied with the material.

Performance

GPU time when the operator recooks: 0.036 ms at 64³, 0.041 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.