i found out that exactly the same can be done without a pixelshader!

Code:

---

material mat_vegetation

{

	effect=

	"	

		texture texSkin1;

		dword mtlSkill1;

		technique vegetation

		{

			pass p0

			{

				Texture[0]=<texSkin1>;



				ZWriteEnable=true;

				AlphaTestEnable=true;

				AlphaRef=<mtlSkill1>;

				AlphaFunc=greater;

				//CullMode=none;

				

				ColorArg1[0]=Texture;

				ColorOp[0]=Modulate2x;

				ColorArg2[0]=Diffuse;

			}

		}

	";

}



starter mat_vegetation_init

{

	...

	mat_vegetation.skill1=pixel_for_vec(vector(127,0,0),0,8888);

}

---

this version even allows to adjust the threshold via the first value of the vector in the starter function!