Adobe AfterEffects Script (JSX):Z fake depth buffer

Z_fake_depth_v20150719.jsx

/*
Adobe AfterEffects Script (JSX)
	fake_depth
		v20150719
*/

////////////////////////////////variable declaration////////////////////////////////
var thisComp= app.project.activeItem;
var selectedLayers= new Array();
var thisLayer = null;
var tmpN,Zpos;
var frontNul,BackNul,thisFill,compW,compH;
var exp = "thisZ = transform.position[2];" + "\n" +
                "frontZ = thisComp.layer(\"Depth_Null_Front\").transform.position[2];" + "\n" +
                "backZ = thisComp.layer(\"Depth_Null_Back\").transform.position[2];" + "\n" +
                "if (thisZ < frontZ){temp = 0}else if(thisZ > backZ){temp = 1}else{temp = (thisZ - frontZ) / (backZ - frontZ)};" + "\n" +
                "[temp, temp, temp,1]";
                
////////////////////////////////body////////////////////////////////
if(thisComp instanceof CompItem){
    selectedLayers = thisComp.selectedLayers;
    if(selectedLayers.length > 0){
        Zpos = compareZ(selectedLayers);
        //  深度クリッピング用nullを作成
        if (typeof(Zpos[0]) == "number" && typeof(Zpos[0]) == "number"){
            app.beginUndoGroup("add_Depth_Null");
            frontNul = create3dNull(thisComp,Zpos[0],"Depth_Null_Front");
            backNul = create3dNull(thisComp,Zpos[1],"Depth_Null_Back");
            app.endUndoGroup();
            // レイヤーに塗りエフェクト、エクスプレッション追加
            app.beginUndoGroup("add_explession");
            for (var i = 0; i < selectedLayers.length; i++) {
                thisFill = selectedLayers[i].property("ADBE Effect Parade").addProperty("ADBE Fill");
                thisFill.property("ADBE Fill-0002").expression = exp;
            };
            app.endUndoGroup();
        };
    } else {
        alert('unselected layer'); 
    };
} else {
    alert('unselected compositon');
};

////////////////////////////////functions////////////////////////////////
// Zを比較
function compareZ(layers){
    var max = null;
    var min = null;
    for (var i = 0; i < layers.length; i++) {
        if (! layers[i].threeDLayer){}else {
			tmpN = layers[i].position.value[2];
			if (typeof(max) == "number") {max = Math.max(max, tmpN)} else {max = tmpN};
			if (typeof(min) == "number") {min = Math.min(min, tmpN)} else {min = tmpN};
        };
    };
    return [min,max];
};
//3Dnullを作成
function create3dNull (comp,value,string){
	var tempNull = comp.layers.addNull();
	tempNull.threeDLayer = true;
	tempNull.position.setValue([(comp.width/2),(comp.height/2),value]);
	tempNull.name = string;
	return tempNull;
};

/*エクスプレッション内容
thisZ = transform.position[2];
frontZ = thisComp.layer("Depth_Null_Front").transform.position[2];
backZ = thisComp.layer("Depth_Null_Back").transform.position[2];

if (thisZ < frontZ){
	temp = 0;
}else if (thisZ > backZ){
	temp = 1;
}else{
	temp = (thisZ - frontZ) / (backZ - frontZ)
};

[temp, temp, temp,1]
*/