In MonoDevelop, the Debug button is greyed out!

• This means that MonoDevelop was unable to find the Unity executable; in the MonoDevelop preferences go to the Unity/Debugger section, and then browse to where your Unity executable is located.

Is there a way to get rid of the welcome page in Mono Develop?

• Yes, there is. In the MonoDevelop preferences, go to the Visual Style section, and uncheck "Load welcome page on startup".

Geforce 7300GT on OSX 10.6.4

• Deferred rendering is disabled because materials are not displayed correctly for Geforce 7300GT on OX 10.6.4; This happens because of buggy video drivers.

On Windows x64, Unity crashes when my script throws a NullReferenceException

• Please apply Windows Hotfix #976038.

Graphics

Slow framerate and/or visual artifacts.

• This may occur if your video card drivers are not up to date. Make sure you have the latest official drivers from your card vendor.

Shadows

I see no shadows at all!

• Shadows are a Unity Pro only feature, so without Unity Pro you won't get shadows. Simpler shadow methods, like using a Projector, are still possible of course.
• Shadows also require certain graphics hardware support. See Shadows page for details.
• Check if shadows are not completely disabled in Quality Settings.
• Shadows are currently not supported for Android and iOS mobile platforms.

Some of my objects do not cast or receive shadows

First, the Renderer has to have Receive Shadows on to have shadows on itself; and Cast Shadows on to cast shadows on other objects (both are on by default).

Next, only opaque objects cast and receive shadows; that means if you use built-in Transparent or Particle shaders then you'll get no shadows. In most cases it's possible to Transparent Cutout shaders (for objects like fences, vegetation etc.). If you use custom written Shaders, they have to be pixel-lit and use Geometry render queue. Objects using VertexLit shaders do not receive shadows either (but can cast shadows just fine).

Finally, only Pixel lights cast shadows. If you want to make sure that some light always casts shadows, no matter how many other lights are in the scene, set it to Force Pixel render mode (see Light documentation).