Direct3D 8 - Pixel Shader - Instructions - lrp

Last edited 2026-02-20

The lrp instruction returns an interpolation of values ​​between x and y, depending on t.

The lrp syntax looks like this:

lrp r, x, y, t;

(This instruction returns a value from the given mathematical function: r = x + (y - x) * t)

r: Value to which the final result will be assigned.

x: First value.

y: Second value.

t:Parameter controlling which result to return. Set to 0.0 to return x, set to 1.0 to return y, and set to 0.5 to return the midpoint (between x and y).

Example code:

texture T_Image;                            // <- Main texture

technique tech_main
{
    pass P0
    {
        Texture[0] = <T_Image>;
        PixelShader = asm
        {
            ps.1.1;                         // <- Pixel shader version

            def c0, 1.0, 0.0, 0.0, 0.5;     // <- Declaration of a constant 0, it's red color
            def c1, 0.0, 0.0, 1.0, 0.0;     // <- Declaration of a constant 1, it's blue color
            
            tex t0;                         // <- Load the T_Image texture

            lrp r0, c0, c1, c0.a;           // <- Linear interpolation between red and blue colors and assigning this to result
            mov r0.a, t0.a;
        };
    }
}

This example requires the following in the .XML file:

• Flag <dx8>yes</dx8>

(More information about .XML files can be found here)

Details table:

Created with the Personal Edition of HelpNDoc: Maximize Your CHM Help File Capabilities with HelpNDoc