for one, as you said, MainGraphics is an abstract class so you can't make an object from it. secondly, you can't add graphics to a frame because the class Graphics2D is not a type of Component. here's a quick graphics example to get what you want to do:

public class Test extends JPanel{

    public Test(){
        JFrame frame = new JFrame("test");
        frame.getContentPane().add(this);
        frame.setSize(300, 300);
        frame.setVisible(true);
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawLine(5, 5, 10, 10);
    }

    public static void main(String[] args){
        new Test();
    }
}


here's my attempt, though my use of pointers is probably pretty ugly since i just used an online tutorial as a reference for that part.

#include <stdio.h>

unsigned long pow(unsigned long base, unsigned long exp)
{
    if(exp == 1)
        return base;
    return base * pow(base, exp - 1);
}

char *GetString(int stringLength, unsigned long combination)
{
    char* character = malloc(sizeof(char) * 2);
    *character = combination % 26 + 'a';
    *(character + 1) = '\0';
    if(stringLength == 1)
        return character;
    return strcat(GetString(stringLength - 1, combination / 26), character);
}

int main(int argc, int *argv[])
{
    const int MAX_LEN = 3;
    int len;
    unsigned long i;
    for(len = 1; len <= MAX_LEN; len++)
    {
        for(i = 0; i < pow(26, len); i++)
        {
            printf("%s\n", GetString(len, i));
        }
    }
    return 0;
}


Can you clarify your question? I thought y-movement is generally independent from x-movement, and since you said walking speed is constant, x = x0 + v0t + .5at2 wouldn't really make much sense.

ok, so i have the variables x, y, and yVel. there's also the constants XVEL, GRAVITY, and JUMP_FORCE. XVEL is how many pixels the character moves right each frame. GRAVITY is how many pixels the character falls each frame (if it can fall). JUMP_FORCE is the initial upward velocity when the user presses space (makes the character jump). i tweaked my engine so that the character jumps at a desire length/height. but now i want to double XVEL, making the character move twice as fast. however, now i need to tweak GRAVITY so that the character falls faster, in order to make sure the length of the jump remains constant. but because i tweaked GRAVITY, now JUMP_FORCE needs to be modified so the height of the jump remains constant as well. however, i don't know how much to modify these constants. and it isn't as simple as doubling GRAVITY and JUMP_FORCE, i already tested that.


edit: alright, i think i've found an equation. if XVEL is multiplied by p, JUMP_FORCE is multiplied by p and GRAVITY is multiplied by p^2.

right now i'm trying to tweak my engine so i can get some data (e.g. what's GRAVITY and JUMP_FORCE when XVEL is multiplied by 2? multiplied by 3? etc...) and then use a regression to find an equation from that. but i was wondering if anyone knew how to figure out the equation mathematically.

bump, anyone?

this question could really go anywhere dev-related, but since my game's being programmed in java i put it here.

Are there any equations which, given a constant horizontal speed, will give a gravitational constant and an acceleration constant (intial upward velocity for when the character jumps) given that the height and length of the jump must remain constant?

i.e., i've programmed my game using a speed of 3 pixels/frame and tweaked the upward velocity and gravity until i liked the height/length of the character's jump. now i want to be able to have a speed of say 6 pixels/frame and have an equation which calculates the upward velocity and gravity so that the height/length of the jump isn't changed from my 3 pixels/frame speed.

i know that x = x₀ + v₀t + .5at², but i am unsure if that can be applied in this case, and if so how.

thanks for the help!

yes, *(array + x + (y * yy)) is the right expression. you should rename your variables for clarity.

also, i just googled that the size of char in c++ is 1 byte, while int is 4 bytes. i think that ashbad is right; you're putting integers into character spaces.

i thought memblock[0] and memblock[1] are for the size? and that code segment starts writing at memblock[2] not memblock[3].

regardless, the code i cited in my first post has an issue, memblock[x * y + 2] and memblock[x * y + 3] are written to when they shouldn't be.

and
*(array + x + (x * y))
should be
*(array + x + (x * yy))


i always do the same thing cooliojazz does for images, although it won't affect the error you're getting scout.

i found a good explanation of how displaymodes work. what i would first do is test if isFullScreenSupported, and then do something similar to what's in the example code in the link. if it isn't, i don't have a solution. if it is, use setFullScreenWindow and see if your code works. if it still doesn't work, do the follow somewhere in the Screen class and copy/paste what's printed out:
for(DisplayMode dm : vc.getDisplayModes())
System.out.println(dm);

then it pick the DisplayMode printed out that's closest to the one in your code and use it:
DisplayMode dm = new DisplayMode(800,600,16,DisplayMode.REFRESH_RATE_UNKNOWN);