Semantics with the SV prefix are "system value" semantics. This means that they have a specific meaning to the pipeline. In the case of SV_Position, if it's attached to a vertex shader output that means that the output will contain he final transformed vertex position used for rasterization. Or if you use it for a pixel shader input, it will contain the screenspace position of the pixel.
http://www.gamedev.net/topic/579610-hlsl-semantics-position-vs-sv_position/
转载于:https://www.cnblogs.com/zhkza99c/archive/2012/07/15/2592710.html
