Direct3D 8 - Pixel Shader - Instructions - sub

Last edited 2026-02-20

The sub instruction assigns the difference of two other values ​​to the selected value.

The sub syntax looks like this:

sub x, y, z;

(This instruction returns a value from the given mathematical function: x = y - z)

x: The value to which the difference of y and z is to be assigned.

y: The first value to be used for the subtraction.

z: The second value to be used for the subtraction.

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, 1.0, 1.0, 0.0;     // <- Declaration of a constant, we treat it as a color (r, g, b, a)

            tex t0;                         // <- Load the T_Image texture

            sub r0, c0, t0;                 // <- Assign the subtraction of colors from the texture and from the constant to the final result: result.rgba = const.rgba - texture.rgba

            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:

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