Direct3D 8 - Pixel Shader - Instructions - dp3

Last edited 2026-02-20

The dp3 instruction computes the three-component dot product of the source registers.

The dp3 syntax looks like this:

dp3 x, y, z;

(This instruction returns a value from the given mathematical function: x = (y.r * z.r) + (y.g * z.g) + (y.b * z.b))

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

y: The first value to be used for the dot product.

z: The second value to be used for the dot product.

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, 0.299, 0.587, 0.114, 0.0;   // <- Declaration of a constant, we treat it as a color (r, g, b, a)

            tex t0;                             // <- Load the T_Image texture

            dp3 r0.rgb, c0, t0;                 // <- Return the luminosity of colors from texture; (t0.r * 0.299) + (t0.g * 0.587) + (t0.b * 0.114)

            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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