/*{
    "CATEGORIES": [
        "Glitch",
        "Retro"
    ],
    "CREDIT": "by Carter Rosenberg",
    "DESCRIPTION": "",
    "INPUTS": [
        {
            "NAME": "inputImage",
            "TYPE": "image"
        },
        {
            "DEFAULT": 4,
            "LABEL": "Line Size",
            "MAX": 50,
            "MIN": 1,
            "NAME": "lineSize",
            "TYPE": "float"
        }
    ],
    "ISFVSN": "2",
    "PASSES": [
        {
            "DESCRIPTION": "this buffer stores the last frame's odd / even state",
            "HEIGHT": "1",
            "PERSISTENT": true,
            "TARGET": "lastRow",
            "WIDTH": "1"
        },
        {
            "PERSISTENT": true,
            "TARGET": "lastFrame"
        }
    ]
}
*/

void main()
{
	//	if this is the first pass, i'm going to read the position from the "lastRow" image, and write a new position based on this and the hold variables
	if (PASSINDEX == 0)	{
		vec4		srcPixel = IMG_PIXEL(lastRow,vec2(0.5));
		//	i'm only using the X and Y components, which are the X and Y offset (normalized) for the frame
		srcPixel.x = (srcPixel.x) > 0.5 ? 0.0 : 1.0;
		gl_FragColor = srcPixel;
	}
	//	else this isn't the first pass- read the position value from the buffer which stores it
	else	{
		vec4		lastRow = IMG_PIXEL(lastRow,vec2(0.5));
		vec2		pixelCoord = isf_FragNormCoord * RENDERSIZE;
		
		if (mod(floor(pixelCoord.y),2.0 * lineSize) < lineSize + lineSize * lastRow.x)
			gl_FragColor = IMG_NORM_PIXEL(inputImage,isf_FragNormCoord);
		else
			gl_FragColor = IMG_NORM_PIXEL(lastFrame,isf_FragNormCoord);
	}
}