pixel world position (2D quad)

Pixel2WorldPos

Vector3 pixelPos = new Vector3(x,y,0); // x,y = texture pixel pos

float planeWidth=transform.renderer.bounds.size.x;
float planeHeight=transform.renderer.bounds.size.y;

// convert to 0-1 uv coords
float localX = ((pixelPos.x / texWidth)-0.5f)*planeWidth;
float localY = ((pixelPos.y / texHeight)-0.5f)*planeHeight;

//Vector3 worldPos = transform.TransformPoint(new Vector3(localX,localY, 0));

Vector3 worldPos = new Vector3(localX,localY, 0);

this only works if ScaleCamera has PixelsToUnits=1