How to use gl_HalfPixel?

[chyyran]

When compiling HLSL for ShaderModel 3.0, SPIRV-Cross inserts a gl_HalfPixel uniform that must be set. What value should this uniform be set to?

[HansKristian-Work]

0.5 / ViewportSize, but technically it's a bit jank, especially for cases where W goes negative. If possible you should set it to 0 and either adjust for integer pixel center in D3D9 through a viewport or projection matrix fixup.