phase

Direct3D 8 - Pixel Shader - Instructions - phase

Last edited 2026-02-20

The phase instruction is intended to split a shader program into two parts; technically, there can be two programs in a single shader.

Shader instructions appearing before the phase instruction are phase 1 instructions.

All other instructions are phase 2 instructions.

Having two phase instructions increases the maximum number of instructions per shader.

An unfortunate side effect of the phase transition is that the alpha component's temporary registers do not persist throughout the transition.

In other words, the alpha component must be reinitialized after the phase instruction.

Phase only works on ps.1.4, newer and older versions of Pixel Shader do NOT support this instruction

The phase syntax looks like this:

phase;

texture img; // <- Main texture

texture bkd; // <- Background texture

technique tech_main

{

pass P0

{

Texture[0] = <img>;

Texture[2] = <bkd>;

PixelShader = asm

{

ps.1.4; // <- Pixel shader version

// --- PHASE 1 --- //

def c0, 1.0, 1.0, 1.0, 1.0; // <- Declaration of a constant, we treat it as a color (r, g, b, a)

texld r0, t0; // <- Load the img texture

texld r1, t0; // <- Load the bkd texture

mul r0, r0, r0; // <- Assign the multiplication of colors from the img with img texture to the final result: result.rgba = img.rgba * img.rgba

phase; // <- Change from phase 1 to phase 2

// --- PHASE 2 --- //

mul r0.rgb, r0, r1; // <- Assign the multiplication of colors from the img with bkd texture to the final result: result.rgba = img.rgba * bkd.rgba

mov r0.a, c0.a; // <- Assigning a new alpha value to 1.0

};

}

Type	Phase instructions	Description	Instruction slots	ps.1.0	ps.1.1	ps.1.2	ps.1.3	ps.1.4	Note
asm	phase	Transition between phase 1 and phase 2	0	No	No	No	No	Yes	Phases allow for almost doubling the number of available instructions for ps.1.4