noperspective

noperspective

Interpolation Modifiers Introduced in Shader Model 4

https://docs.microsoft.com/zh-cn/windows/desktop/direct3dhlsl/dx-graphics-hlsl-struct

Vertex shader outputs that are used for pixel shader inputs are linearly interpolated to get per-pixel values during rasterization. To set the method of interpolation, use any of the following values, which are supported in shader model 4 or later. The modifier is ignored on any vertex shader output that is not used as a pixel shader input.

Interpolation Modifier	Description
linear	Interpolate between shader inputs; linear is the default value if no interpolation modifier is specified.
centroid	Interpolate between samples that are somewhere within the covered area of the pixel (this may require extrapolating end points from a pixel center). Centroid sampling may improve antialiasing if a pixel is partially covered (even if the pixel center is not covered). The centroid modifier must be combined with either the linear or noperspective modifier.
nointerpolation	Do not interpolate .
noperspective	Do not perform perspective-correction during interpolation. The noperspective modifier can be combined with the centroid modifier.
sample	Available in shader model 4.1 and laterInterpolate at sample location rather than at the pixel center. This causes the pixel shader to execute per-sample rather than per-pixel. Another way to cause per-sample execution is to have an input with semantic SV_SampleIndex, which indicates the current sample. Only the inputs with sample specified (or inputting SV_SampleIndex) differ between shader invocations in the pixel, whereas other inputs that do not specify modifiers (for example, if you mix modifiers on different inputs) still interpolate at the pixel center. Both pixel shader invocation and depth/stencil testing occur for every covered sample in the pixel. This is sometimes known as supersampling. In contrast, in the absence of sample frequency invocation, known as multisampling, the pixel shader is invoked once per pixel regardless of how many samples are covered, while depth/stencil testing occurs at sample frequency. Both modes provide equivalent edge antialiasing. However, supersampling provides better shading quality by invoking the pixel shader more frequently.

1. When using an int/uint type, the only valid option is **nointerpolation**.

Interpolation modifiers can be applied to structure members or function arguments, or both.

Examples

Here are some example structure declarations.

struct struct1
{
  int    a;
}

This declaration includes an array.

struct struct2
{
  int    a;
  float  b;
  int4x4 iMatrix;
}

This declaration includes an interpolation modifier.

struct In
{
  centroid float2 Texcoord;
};