TGC requires a DirectX11 compatible graphics card.
When you see this error message "Fatal error direct3d 11 compute shaders are not available". This means that there is no DirectX11 compatible graphics card installed or the graphics card drivers are not installed.
To check if your computer's graphics card is DirectX 11 compatible. In Windows, open the search/start bar and type dxdiag, then select it from the results. The window that pops up shows you your DirectX version.
1) Under the "Systems" tab it will tell you your current DirectX version.
2) Under the "Display" tab, the "Feature Levels" (sometimes listed as DDI version) will tell you the versions of Direct X your card can handle. This should say 11, 11_1, 11_2, 12 or something. When it only says 10, 10_1, 10_2 etc or 9 its not DirectX11 compatible.