Installation and requirements
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Installation and requirements

Requirements

  • Windows
  • an NVIDIA RTX 30-series GPU or newer, with driver R590 or newer (OptiX 9.1). An older card or driver makes the HRLW Path Tracer TOP show an error saying which.
  • TouchDesigner 2025.30000 or later

Install

  1. Close TouchDesigner. It keeps loaded plugin files locked.
  2. Copy the HRLW plugin files (the DLLs, LICENSE.txt and THIRD_PARTY_NOTICES.txt) into Documents/Derivative/Plugins/Harlow. A Plugins folder next to a .toe file also works, for a project that carries its own copy.
  3. Keep all HRLW files together in that one folder, and load only one copy of the HRLW Path Tracer DLL. The other operators share its GPU data and must talk to the same copy.
  4. Start TouchDesigner. The operators appear in the OP Create dialog among the custom operators, in the TOP and POP tabs.

Activate

Harlow needs a license key on each computer. Until it has one, every HRLW operator shows an error with this computer's machine code and does nothing.

  1. On any HRLW operator's License page, press Activate Online. This opens the claim page. On a computer without internet, open the claim page on your phone instead and type in the machine code shown in the error (Copy Machine Code copies it).
  2. Log in with Patreon and activate the computer. Up to 3 computers per patron.
  3. Copy the key and press Paste Key on the License page. Every HRLW operator starts working within a second. Middle-click the HRLW Path Tracer TOP to see who it's licensed to.

The key is saved in %LOCALAPPDATA%\Harlow\license.key, not in your project, so sharing a .toe doesn't share it. A key covers every build released while you were subscribed, forever. A newer build asks for a fresh key, which the claim page gives while you're subscribed.

On the first start after an update, the renderer compiles in the background (a minute or two the first time); the HRLW Path Tracer TOP is black and shows a warning until it is ready.