Shader model support for Windows Phone 8
Applies to: Windows Phone 8 and Windows Phone Silverlight 8.1 only
On Windows Phone 8, developers can use custom vertex shaders and pixel shaders in apps that use Direct3D. The supported features and limitations of custom shaders on Windows Phone 8 devices are defined by the shader model 4_0_level_9_3. For more info on shader models, see Shader Model vs. Shader Profiles.
The 4_0_level_9_3 shader model encompasses all of the features of the Direct3D 9-era shader model 2.0 with several important differences.
Shaders must be written in High Level Shading Language for DirectX. For more info, see HLSL.
Static and dynamic flow control is supported.
Vertex shaders may be up to 256 equivalent shader assembler instructions in length.
Pixel shaders may be up to 512 equivalent shader assembler instructions in lenth.
HLSL is a C-like programming language optimized for writing GPU shader code. When writing shader code in HLSL for use in Windows Phone 8 apps, you should consider the following:
Shader code must be compiled offline using FXC.exe, the effect-compiler tool. This is used by Visual Studio by default and can also be invoked from the command line. Runtime shader compilation is not supported.
The shader compiler targets for 4_0_level_9_3 are vs_4_0_level_9_3 for vertex shaders and ps_4_0_level_9_3 for pixel shaders. For more info on shader compiler targets, see Specifying Compiler Targets.
The semantics for the 4_0_level_9_3 shader model are the same as those documented for Direct3D 9 and, as a result, most system-value semantics, introduced with Direct3D 10 and shader model 4.0, are not available. The exceptions to this are SV_Position, SV_Target, and SV_Depth, which are supported. For more info on semantics, including system-value semantics, see Semantics.
When writing larger shaders that may be approaching the instruction count limits, you can use the “/Fc” switch when compiling a shader to obtain and review the resulting assembler code output. For more information on command line options for the effect compiler tool, see Syntax.