segaconsoles

Pixel art Sega consoles by BLUEamnesiac

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In this example I show how to use a big plane map (64x64 tiles) and how to set vdp registers so that plane B's map will not interfer with hscroll memory in vram. The background is moved by a set of data that is generated from a sine easing function which moves plane B's HSCROLL and VSCROLL with an offset of 90 degrees so the movement is circular.

This is my PHP function that I wrote to create the data. It can be easily adopted for other easing data.

<pre>
<?php 
// t: current time
// b: start value
// c: change in value
// d: duration
//
// t and d can be frames and/or (milli)seconds

function easeOutQuad($t, $b, $c, $d) {
    $t /= $d;
	return ($c*-1) * $t * ($t-2) + $b;
};
function easeInQuad($t, $b, $c, $d) {
	$t /= $d;
	return $c*$t*$t + $b;
};
function easeInSine($t, $b, $c, $d) {
	return ($c*-1) * cos($t/$d * (pi()/2)) + $c + $b;
};

function easeInOutSine($t, $b, $c, $d) {
    $c = -1 * abs($c);
	return $c/2 * (cos(pi()*$t/$d) - 1) + $b;
};

$seconds    = 15;            // Enter time in seconds
$duration   = (60*$seconds); // 60fps * x = xsec
$start      = 0;
$end        = 1024;
$array      = [];

for($frame=0; $frame <= $duration; $frame++){
    $val = easeInOutSine($frame, $start, $end, $duration); // select easing function here
    $array[] = $val;
}


// Change from here to whatever fits your need of formatting the data:

echo 'sine:' . "\n";
foreach($array as $val){
    echo "\t".'dc.w' . "\t" . '$' . strtoupper(dechex(round($val))) . "\n";
}

$array = array_reverse($array);

foreach($array as $val){
    echo "\t".'dc.w' . "\t" . '$' . strtoupper(dechex(round($val))) . "\n";
}
echo 'sineEnd:' . "\n";
?>
</pre>