3D animation - interacting masses

<?php
function cubeLatticeArray($a, $b){
  //$a is the radius of the larger sphere, $b is the radius of the smallers spheres that are fitting into the larger sphere.
  //This function will only solve for one eighth of the cube. I will later have this function copy these results over
  //to the other 7 parts of the sphere.
  $radius = pow($a, 2);
    $points[0] = array('x' => $b, 'y' => $b, 'z' => sqrt(pow($a, 2)-pow(2*$b, 2))-$b); //I solved this line for myself, stfu
    $pass = true;
    for($i = 1; $pass == true; $i++){
        $current = end($points);
        if($radius > (pow($current['x']+$b, 2)+pow($current['y']+3*$b, 2)+pow($current['z']+$b, 2))){
            //Move to the next Y cube relative to the last exact position
            $points[$i] = array('x' => $current['x'], 'y' => $current['y']+2*$b, 'z' => $current['z']);
        }elseif($radius > (pow($current['x']+3*$b, 2)+pow(2*$b, 2)+pow($current['z']+$b, 2))){
            //Move to the next X cube relative to the last Z and X position (not Y)
            $points[$i] = array('x' => $current['x']+2*$b, 'y' => $b, 'z' => $current['z']);
        }elseif($radius > (pow(2*$b, 2)+pow(2*$b, 2)+pow($current['z']-3*$b, 2)) && $current['z']-3*$b >= 0){
            //Move to the next Z cube relative to the last Z value (not x or y)
            $points[$i] = array('x' => $b, 'y' => $b, 'z' => $current['z']-2*$b);
        }else{
            $pass = false;
            $total = $i;
        }
    }
    foreach($points as $key => $value){
        $total++;
        $points[$total]['x'] = -$value['x'];
        $points[$total]['y'] = -$value['y'];
        $points[$total]['z'] = -$value['z'];
        $total++;
        $points[$total]['x'] = -$value['x'];
        $points[$total]['y'] = $value['y'];
        $points[$total]['z'] = -$value['z'];
        $total++;
        $points[$total]['x'] = -$value['x'];
        $points[$total]['y'] = -$value['y'];
        $points[$total]['z'] = $value['z'];
        $total++;
        $points[$total]['x'] = $value['x'];
        $points[$total]['y'] = -$value['y'];
        $points[$total]['z'] = -$value['z'];
        $total++;
        $points[$total]['x'] = -$value['x'];
        $points[$total]['y'] = $value['y'];
        $points[$total]['z'] = $value['z'];
        $total++;
        $points[$total]['x'] = $value['x'];
        $points[$total]['y'] = -$value['y'];
        $points[$total]['z'] = $value['z'];
        $total++;
        $points[$total]['x'] = $value['x'];
        $points[$total]['y'] = $value['y'];
        $points[$total]['z'] = -$value['z'];
    }
    echo "$total </br>";
    return $points;
}

function minAngle($line, $p, $threshold, $focus, $depth){
    //---Find the side lengths of the triangle created by the point and the line
    $b = pow($line['x'][1]-$line['x'][2], 2)+pow($line['y'][1]-$line['y'][2], 2)+pow($line['z'][1]-$line['z'][2], 2); //Difference between the two points of the line
    $c = pow($line['x'][1]-$p['x'], 2)+pow($line['y'][1]-$p['y'], 2)+pow($line['z'][1]-$p['z'], 2); //Difference between the start of the line and the point
    $a = pow($p['x']-$line['x'][2], 2)+pow($p['y']-$line['y'][2], 2)+pow($p['z']-$line['z'][2], 2); //difference between the end of the line and the point
    //---Find the angle formed between the ray and the point
    $angle = rad2deg(acos(($b+$c-$a)/(2*sqrt($b)*sqrt($c)))); //cos^(-1)((b^2 + c^2 - a^2) / 2bc), will give the angle between the point an the ray.

    //---Find out how out of focus the point is
    $dif = intval(abs($p['y']-$focus)/$depth);
    if($dif == 0){
        $dif = 1;
    }
    if($angle < $threshold*$dif){
        //---Depending on the angle formed and the level of focus, return the brightness of the ray/pixel.
        $return = intval((($threshold*$dif-$angle)/($threshold*$dif))*255);
        return $return;
    }else{
        return 0;
    }
}

function movePoint($current_point, $other_points, $mass, $time_interval){
    //Given the above information, this function will return the resulting point after it has been affected by the gravity of the other points.
    /* Basically the method is:
        -Find the distance between the given point, and another of the rest of the points
        -Find the net force experienced by the point
        -Separate net force into the X, Y and Z planes.
        -Repeat steps 1-3, summing up the separated forces.
        -Then, a = G*((m1*m2)/(r^2))/m1
        -I guess that the period is going to affect the velocity, and then displacement... how does it go again. :S
        -s = ut+1/2at^2
        -...I'm going to need more information from the $current_point, I believe. Going to need velocity aswell.
        -shit...
    */
    $net['x'] = 0;
    $net['y'] = 0;
    $net['z'] = 0;

    $dif['x'] = 0;
    $dif['y'] = 0;
    $dif['z'] = 0;
    foreach($other_points as $key => $other){
        //I suck at creating variable names
        //And I didn't really think this through
        if($current_point['x'] != $other['x'] && $current_point['y'] != $other['y'] && $current_point['z'] != $other['x']){
            $dif['x'] = $other['x']-$current_point['x'];
            $dif['y'] = $other['y']-$current_point['y'];
            $dif['z'] = $other['z']-$current_point['z'];
            $distance = sqrt(pow($dif['x'], 2)+pow($dif['y'], 2)+pow($dif['z'], 2)); //Pretty much the radius
            $acceleration = ((6.67300*pow(10, -11)*pow($mass, 2))/pow($distance, 2))/$mass; //I guess that's right
            echo "acc = $acceleration </br> \n";
            //now to divide this into the 3 planes, x, y and z
            if($dif['x'] < 0){
                $multiplier['x'] = -1;
            }elseif($dif['x'] == 0){
                $multiplier['x'] = 0;
            }else{
                $multiplier['x'] = 1;
            }

            if($dif['y'] < 0){
                $multiplier['y'] = -1;
            }elseif($dif['y'] == 0){
                $multiplier['y'] = 0;
            }else{
                $multiplier['y'] = 1;
            }

            if($dif['z'] < 0){
                $multiplier['z'] = -1;
            }elseif($dif['x'] == 0){
                $multiplier['z'] = 0;
            }else{
                $multiplier['z'] = 1;
            }

            $output_acceleration['x'] += $multiplier['x']*abs($acceleration*cos(acos($dif['x']/$distance)));
            $output_acceleration['y'] += $multiplier['y']*abs($acceleration*cos(acos($dif['y']/$distance)));
            $output_acceleration['z'] += $multiplier['z']*abs($acceleration*cos(acos($dif['z']/$distance)));

            echo "acc (" . $output_acceleration['x'] . ", " . $output_acceleration['y'] . ", " . $output_acceleration['z'] . ") </br> \n";
            //That was more simple that I thought.
        }else{
            $current_key = $key;
        }
        $displacement['x'] = $current_point['xv']*$time_interval+0.5*$output_acceleration['x']*pow($time_interval, 2); // s = ut+(1/2)at^2
        $displacement['y'] = $current_point['yv']*$time_interval+0.5*$output_acceleration['y']*pow($time_interval, 2); // s = ut+(1/2)at^2
        $displacement['z'] = $current_point['zv']*$time_interval+0.5*$output_acceleration['z']*pow($time_interval, 2); // s = ut+(1/2)at^2
        global $points;
        $points[$current_key]['xv'] = $displacement['x']/$time_interval;
        $points[$current_key]['yv'] = $displacement['y']/$time_interval;
        $points[$current_key]['zv'] = $displacement['z']/$time_interval;
    }
    $current_point['x'] += $displacement['x'];
    $current_point['y'] += $displacement['y'];
    $current_point['z'] += $displacement['z'];
    //Holy shit, I think that's done. This isn't written the most efficiently, but it will do.
    return $current_point;
}

//---Variables
$screen_dimensions = array('height' => 100, 'width' => 100); //Do not make this very large as too much memory/time will be used and the program will fail.
$screen_position = array('x' => 0, 'y' => -20, 'z' => 0); //I spose this could be changed, but I haven't bothered with it.

$amount_of_frames = 2; //1 second = 1 frame

$screen_viewingAngle = 65; //In degrees
//$focus = (0.5*$screen_dimensions['width'])/tan(deg2rad(0.5*$screen_viewingAngle))+70; //The Y frame which will be in focus.
$focus = 798;
$depth_of_field = 150; //This is kinda like the F-stop on a lens.
$angular_threshold = 1; //This is kinda different, but it's basically the accuracy of the imaging. 0 would be perfect, but would not work.
/* Do not use these yet.
$screen_yaw = 0;
$screen_pitch = 0;
$screen_roll = 0;
*/

/* BEGIN MAIN PROGRAM */

//---Pre-processing variables (inititators of a sort)
$offset['y'] = (0.5*$screen_dimensions['width'])/tan(deg2rad(0.5*$screen_viewingAngle))+$screen_position['y'];
//$offset['x'] = 0.5*$screen_dimensions['width']+$screen_position['x']; NOT USED
$offset['z'] = 0.5*$screen_dimensions['height']-$screen_position['z'];

$funny_variable[1] = 0.5*$screen_dimensions['width'];
$funny_variable[2] = 0.5*$screen_dimensions['width']+$screen_position['x'];

//$points = cubeLatticeArray(800, 77);
$points[1] = array('x' => 0, 'y' => 0, 'z' => 0);
$points[2] = array('x' => 50, 'y' => 10, 'z' => 50);
foreach($points as $key => $value){
    //Make the velocity on each of the points zero (initiate variables)
    $points[$key]['xv'] = 0;
    $points[$key]['yv'] = 0;
    $points[$key]['zv'] = 0;
}
//---Reset '$current' variables
for($h = 0; $h < $amount_of_frames; $h++){
    $current['z'] = $offset['z'];
    $current['x'] = $screen_position['x']-$funny_variable[1];

    //---Begin writing file
    unlink("image$h.ppm"); //file that we will be editing, we are are deleting the file so we have a clean file to work on
    $fh = fopen("image$h.ppm", 'a+'); //creates the image file that we will be editting and opens the file for appending

    $print_height = 1+$screen_dimensions['height'];
    $print_width = 1+$screen_dimensions['width'];

    $startWrite = "P3\n# image$h.ppm\n$print_width $print_height\n255"; //fomatting the ppm file
    fwrite($fh, $startWrite);

    //---Begin building rays and printing the file
    //These two steps are done at the same time for efficiency, and memory
    for($i = 0; $i < ($print_height*$print_width); $i++){
        //---Origin points
        $lines['x'][1] = $screen_position['x'];
        $lines['y'][1] = $screen_position['y'];
        $lines['z'][1] = $screen_position['z'];

        //---Resolve when to move to the next row of pixels
        if($i > 0){
            $current['x']++;
        }
        if($current['x'] > $funny_variable[2]){
            $current['x'] = -$funny_variable[1]+$screen_position['x'];
            $current['z']--;
        }
        //---To points
        $lines['x'][2] = $current['x'];
        $lines['y'][2] = $offset['y'];
        $lines['z'][2] = $current['z'];

        if($i%5 == 0){ //basic formatting decides when a new line must be placed
            $Nl = " \n";
        }else{
            $Nl = " ";
        }
        $out = 000;
        foreach($points as $value){
            $colour = minAngle($lines, $value, $angular_threshold, $focus, $depth_of_field);
            if($colour == 255){
                $out = $colour;
                break 1;
            //}elseif($colour >= 0 && $colour >= $out){
            }elseif($colour >= 0){
                $out = str_pad(intval($colour+$out), 3, "0", STR_PAD_LEFT);
                if($out >= 255){
                    $out = 255;
                    break 1;
                }
            }
        }
        printf("(%+'04.2d, %+'04.2d, %+'04.2d) = %'03d </br>", $lines['x'][2], $lines['y'][2], $lines['z'][2], $out);
        //echo "(".$lines['x'][2].", ".$lines['y'][2].", ".$lines['z'][2].")= $out </br>\n";
        $write = "$Nl$out $out $out"; //the line that is to be outputted
        fwrite($fh, $write); //write the pixel to the file.
    }
    fclose($fh);
    foreach($points as $key => $value){
        $points[$key] = movePoint($value, $points, 1000, 1);
    }
}
?>