1. A method for determining whether a pixel at predetermined pixel co-ordinates in an area being rasterized is within a triangle defining a sub-area of the area, the triangle being defined by first, second and third coordinate pairs representing the triangle's vertices, the method including the steps of: translating a coordinate system in relation to which the triangle is defined, such that the pixel co-ordinates are disposed at an origin of the coordinate system; calculating determinants of matrices defined by the coordinate values of at least two of the vertices; identifying the signs of the determinants; and determining whether the pixel is within the triangle on the basis of the signs of the determinants.