Rendering upgrade details

Unity 3 brings a lot of graphics related changes, and some things might need to be tweaked when you upgrade existing Unity 2.x projects. For changes related to shaders, see Shader Upgrade Guide.

Forward Rendering Path changes

Unity 2.x had one rendering path, which is called Forward in Unity 3. Major changes in it compared to Unity 2.x:

• Most common case (one directional per-pixel light) is drawn in one pass now! (used to be two passes)
• Point & Spot light shadows are not supported. Only one Directional light can cast shadows. Use Deferred Lighting path if you need more shadows.
• Most "Vertex" lights replaced with Spherical Harmonics lighting.
• Forward rendering path is purely shader based now, so it works on OpenGL ES 2.0, Xbox 360, PS3 (i.e. platforms that don't support fixed function rendering).

Shader changes

See Shader Upgrade Guide for more details. Largest change is: if you want to write shaders that interact with lighting, you should use Surface Shaders.

Obscure Graphics Changes That No One Will Probably Notice ^TM

• Removed Mac Radeon 9200 pixel shader support (!!ATIfs assembly shaders).
• Removed support for per-pixel lighting on pre-ShaderModel2.0 hardware. As a result, Diffuse Fast shader is just VertexLit now.
• Removed non-attenuated lights. All point and spot lights are attenuated now.
• Removed script callbacks: OnPreCullObject and RenderBeforeQueues attribute.
• Removed p-buffer based RenderTextures. RenderTextures on OpenGL require FBO support now.
• Most Pass LightMode tags are gone, and replaced with new tags. You should generally be using Surface Shaders for that stuff anyway.
• Texture instanceIDs are not OpenGL texture names anymore. Might affect C++ Plugins that were relying on that; use texture.GetNativeTextureID() instead.
• Rename shader keywords SHADOWS_NATIVE to SHADOWS_DEPTH; SHADOWS_PCF4 to SHADOWS_SOFT.
• Removed ambient boost on objects that were affected by more than 8 vertex lights.
• Removed _ObjectSpaceCameraPos and _ObjectSpaceLightPos0 (added _WorldSpaceCameraPos and _WorldSpaceLightPos0).
• LightmapMode tag in shader texture property does nothing now.
• Skybox shaders do not write into depth buffer.
• GrabPass (i.e. refractive glass shader) now always grabs texture of the size of the screen.
• #pragma multi_compile_vertex and #pragma multi_compile_fragment are gone.
• Polygon offset in ShaderLab can't reference variables anymore (like Offset [_Var1], [_Var2]).
• Renamed TRANSFER_EYEDEPTH/OUTPUT_EYEDEPTH to UNITY_TRANSFER_DEPTH/UNITY_OUTPUT_DEPTH. They also work on a float2 in Unity 3.
• Removed special shader pass types: R2TPass, OffscreenPass.
• Removed _Light2World0, _World2Light0 built-in shader matrices.
• Removed _SceneAmbient, _MultiModelAmbient, _MultiAmbient, _ModelAmbient, _MultiplyFog, _LightHackedDiffuse0, _ObjectCenterModelLightColor0 built-in shader vectors.
• Removed _FirstPass built-in shader float.
• Fog mode in shader files can't come from variable (like Fog { Mode [_MyFogMode] }). To use global fog mode, write Fog { Mode Global }.
• Removed BlendColor color from ShaderLab.
• Removed support for declaring texture matrix by-value in shader property.
• Removed support for "static" shader properties.
• Removed support for texture border color (RenderTexture.SetBorderColor).
• Removed ColorMaterial Ambient, Diffuse, Specular support (ColorMaterial AmbientAndDiffuse & Emission left). Support for the removed ones varied a lot depending on the platform causing confusion; and they didn't seem to be very useful anyway.
• Built-in _CameraToWorld and _WorldToCamera matrices now do what you'd expect them to do. Previously they only contained the rotation part, and camera-to-world was flipped on Y axis. Yeah, we don't know how that happened either :)
• Removed Shader.ClearAll(). Was deprecated since 2007, time to let it go.
• Vertex shaders are compiled to Shader Model 2.0 now (before was 1.1). If you want to compile to SM1.1, add #pragma target 1.1 in the shader.

Page last updated: 2010-09-25

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