Terms of Use for Wetpress

Wetpress: Watercolor Painting Published by OFO Labs

Last Updated: September 2026

Please read these Terms of Use before using Wetpress. By downloading or using the app, you agree to them.

Acceptance of Terms

By accessing or using Wetpress, developed and published by OFO Labs, you agree to be bound by these Terms of Use. If you do not agree, do not use the app.

The App

Wetpress is a watercolour painting instrument for iPhone. The paint in it is simulated rather than drawn: the app solves the movement of water over paper many times a second and works out where the pigment ends up. Everything runs on your device and the app makes no network requests.

What we claim about the simulation, and what we do not

We think this belongs in the terms rather than only in the marketing.

Wetpress implements the shallow water and pigment transfer model published by Curtis, Anderson, Seims, Fleischer and Salesin in Computer-Generated Watercolor (SIGGRAPH 1997), with Kubelka-Munk two constant optics for how layers of transparent paint combine. Water flows over the sheet under a solved pressure field, the fibres of the paper absorb it and carry it sideways, pigment is advected by that flow and settles into the paper at a rate that depends on the pigment, on how wet the paper still is, and on the depth of the tooth beneath it. Our tests assert the physical behaviour rather than the appearance: that pigment is neither created nor destroyed, that a wash left to dry ends up denser at its rim than at its centre, that the pits of a rough sheet hold more than twice the pigment its peaks do while a smooth sheet does not, that clean water dropped into a setting wash lifts the middle and piles a ring outside it, and that a staining pigment resists being lifted while a granulating one does not.

That is a model of watercolour, and a model is not watercolour. Real paint on real paper is affected by humidity, by the angle you hold the block at, by the exact brush, by the sizing of that particular sheet and by how the pigment was ground. Wetpress reproduces the behaviours that make the medium recognisable; it does not claim to predict what a specific tube of paint would do on a specific sheet. The twelve pigments carry the Colour Index names of real pigments and are set up to behave the way those pigments are known to behave, but their optical constants are derived from each pigment's appearance rather than measured in a laboratory. Treat the app as an instrument, not as a colour proofing tool.

Your paintings are yours

Anything you paint in Wetpress belongs to you. We claim no rights over it, we never see it, and we cannot use it. Exported images are yours to do anything with, including commercially.

Purchases

Wetpress is downloaded at no charge and includes three pigments, one paper and the complete simulation. A single non consumable in app purchase, The Whole Tin, unlocks the remaining nine pigments, the other three papers, and export at four times the size. It is a one time payment. There is no subscription of any kind, and there never will be one in this app.

Purchases are handled entirely by Apple. Refunds are handled by Apple under the terms of the Apple Media Services agreement, not by us, and we cannot issue them. The unlock is tied to your Apple Account and can be restored on any device signed in to it, from the Restore purchase button on the unlock screen.

Acceptable use

Do not decompile, reverse engineer or redistribute the app, and do not attempt to bypass the purchase. These are the ordinary terms; nothing unusual is intended by them.

Disclaimer and liability

The app is provided as is, without warranties of any kind. To the fullest extent the law allows, OFO Labs is not liable for any loss arising from your use of it, including the loss of a painting. Paintings live on your device: keep device backups on if they matter to you. Nothing here limits any right you have under mandatory consumer law in your country.

Changes

We may update these terms. The current version is always at https://ofolabs.net/wetpress/terms with the date it was last changed.

Contact

ofolabs@gmail.com