SVPOSITION

SVPOSITION is a term used in shader programming to refer to the system-value that carries position information through the graphics pipeline. The official and widely used name in Direct3D/HLSL is SV_POSITION; some codebases or documentation spell it without the underscore as SVPOSITION, treating it as an alias or shorthand. It denotes the position data produced by the vertex shader and consumed by later stages.

In a vertex shader, SVPOSITION is typically a float4 that represents the vertex’s position in clip space (xyzw) after projection. This value undergoes perspective division and viewport transformation to become window or screen-space coordinates. In a subsequent pixel shader, SV_POSITION can be read as an input that reflects the pixel’s position within the render target, enabling screen-space calculations and effects.

SV_POSITION is a special system-value semantic. It is not treated like ordinary interpolated varyings; the position data used for rasterization is determined by the pipeline, and the per-fragment value supplied to the pixel shader corresponds to the actual pixel location being shaded. Other per-vertex outputs are interpolated normally, but SV_POSITION itself is used to drive rasterization and depth/stencil logic rather than to convey arbitrary interpolants.

Common uses include post-processing and screen-space effects where knowledge of the pixel’s location is necessary, as well as debugging or alignment tasks that require knowing exact screen-space position. The canonical term remains SV_POSITION, while SVPOSITION appears as a variant in some codebases.