import algebra.*;

/**
 * The PerspectiveCorrectRasterizer class extends Rasterizer to perform
 * Persepctive Correct interpolation
 * of attributes.
 *
 * @author cdehais
 */
public class PerspectiveCorrectRasterizer extends Rasterizer {

    public PerspectiveCorrectRasterizer(Shader shader) {
        super(shader);
    }

    /**
     * Rasterizes the triangular face made of the Fragment v1, v2 and v3
     */
    public void rasterizeFace(Fragment v1, Fragment v2, Fragment v3) {
        Matrix C = makeBarycentricCoordsMatrix(v1, v2, v3);

        /* iterate over the triangle's bounding box */
        int xmin = Math.min(v1.getX(), Math.min(v2.getX(), v3.getX()));
        int ymin = Math.min(v1.getY(), Math.min(v2.getY(), v3.getY()));
        int xmax = Math.max(v1.getX(), Math.max(v2.getX(), v3.getX()));
        int ymax = Math.max(v1.getY(), Math.max(v2.getY(), v3.getY()));

        Fragment fragment = new Fragment(0, 0);
        int numAttributes = fragment.getNumAttributes();
        try {
            for (int x = xmin; x <= xmax; x++) {
                for (int y = ymin; y <= ymax; y++) {

                    /* setup position now to allow early clipping */
                    fragment.setPosition(x, y);
                    if (!shader.isClipped(fragment)) {

                        Vector3 v = new Vector3(1.0, (double) x, (double) y);
                        Vector bar = C.multiply(v);

                        if ((bar.get(0) >= 0.0) && (bar.get(1) >= 0.0) && (bar.get(2) >= 0.0)) {

                            double oneOverZ = bar.get(0) / v1.getDepth() +
                                    bar.get(1) / v2.getDepth() +
                                    bar.get(2) / v3.getDepth();

                            for (int i = 0; i < numAttributes; i++) {

                                double aOverZ = bar.get(0) * v1.getAttribute(i) / v1.getDepth() +
                                        bar.get(1) * v2.getAttribute(i) / v2.getDepth() +
                                        bar.get(2) * v3.getAttribute(i) / v3.getDepth();

                                fragment.setAttribute(i, aOverZ / oneOverZ);
                            }
                            shader.shade(fragment);
                        }
                    }
                }
            }
        } catch (SizeMismatchException e) {
            /* should not reach */
            e.printStackTrace();
        }
    }
}