CODEWITHSUNDEEP
javaandroid
ProJs er
ProJs er

Reputation: 45

Java ArrayList performance

public static ArrayList<Double> Cast(double angle,double step,ArrayList<Double> list){
    double x = px + Math.sin(angle/180*Math.PI)*step;
    double z = pz + Math.cos(angle/180*Math.PI)*step;

    if((int)x<0||(int)x>mapWidth-1||(int)z<0||(int)z>mapHeight-1){
        return list;
    }else{
        step+=quality;
        list.add(getHeight(x,z));
        return Cast(angle,step,list);
    } 
}

I am making a raycaster and this function return height of (direction,distance). As I need to cast almost fov/screenWidth times, this is very expensive for my application. How can I make dynamic array faster with recursion function?

Upvotes: 0

Views: 95

Answers (1)

noiaverbale
noiaverbale

Reputation: 1678

Recursion functions aren't efficient, althought they resolve difficult problems in an easy way.

When you need to improve performance of a recursion function you'll probably get the best result implementing it iteratively (if possible).

Hope this piece of code helps you!

public static List<Double> cast(double angle, double step, List<Double> list) {
    while(true) {
        double x = px + Math.sin(angle / 180 * Math.PI) * step;
        double z = pz + Math.cos(angle / 180 * Math.PI) * step;

        if ((int) x < 0 || (int) x > mapWidth - 1 || (int) z < 0 || (int) z > mapHeight - 1) {
            break;
        }

        list.add(getHeight(x,z));
        step += quality;
    }

    return list;
}

Upvotes: 2

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