TruForm was an early tessellation implementation created by ATI and employed in DirectX 8, DirectX 9 and OpenGL graphics cards, on both Mac and Windows. The technology was first employed on the Radeon 8500 in 2001. It was never accepted into the DirectX or OpenGL specifications.
Before the adoption of pixel shader-enhanced bump mapping methods such as normal and parallax mapping that simulate higher mesh detail, curved 3D shapes in games were created with large numbers of triangles. The more triangles are used, the more detailed and thus less polygonal the surface appears. TruForm creates a curved surface using the existing triangles, and tessellates this surface to make a new, more detailed polygonal model. It is designed to increase visual quality, without significantly impacting frame rates, by utilizing hardware processing of geometry.
TruForm was not significantly accepted by game developers because it ideally required the models to be designed with TruForm in mind. To enable the feature without causing visual problems, such as ballooned-up weapons, the models had to have flags identifying which areas were to be tessellated. The lack of industry-wide support of the technique from the competition caused developers to ignore the technology.
In later version of Catalyst drivers, the TruForm feature is removed.
Beginning with Radeon X1000 series, TruForm was no longer advertised as a hardware feature. However, Radeon 9500 and higher (as well as hardware supporting Shader Model 3.0) include Render to Vertex Buffer feature, which can be used for tessellation applications. In the case of Radeon X1000 series, it supports binding up to 5 R2VB buffers simultaneously. Tessellation as dedicated hardware has returned in Xenos and Radeon R600 GPUs.
Games with TruForm support
- Counter-Strike (ati_subdiv "2.0", ati_npatch "1.0")
- Tom Clancy's Rainbow Six
- Soldier of Fortune
- Soldier of Fortune II: Double Helix
- Quake (TruQuake Patch)
- Quake 2 (TruQuake2 Patch)
- Hexen II (TruHexen2 Patch)  (developed by RaVeN )
- Unreal Tournament (TruUT Patch)
- The Elder Scrolls III: Morrowind (unofficially, with the FPS Optimizer )
- Madden NFL 2004
- Return to Castle Wolfenstein
- Serious Sam
- Unreal Tournament 2003 and 2004 (must edit the game's ".ini" file and set "UseNPatches=True")
- Wolfenstein: Enemy Territory
- Command & Conquer: Renegade
- Neverwinter Nights (must edit the game's ".ini" file and set "Enable Truform=1")
- FTEQW (Quake World, Net Quake, Quake II, Quake, Quake III: Arena, Hexen 2, Nexuiz)  
- Quake III Arena  (developed by RaVeN )
- Witheiler, Matthew. ATI TRUFORM Technology - Powering the next generation Radeon, Anandtech, May 29, 2001.
- Official ATI's List of TruForm Enabled Game Titles
- ATI Press release
- ATI TruForm Developer FAQ page
- TruForm whitepaper
- R2VB Programming (March 2006)
- Render to Vertex Buffer with D3D9
- area3d.net: NitroGL Demos - home of TruQuake, TruQuake2 & TruUT