自制渲染引擎的ZBuffer问题

Question

我的渲染引擎中的zbuffer有问题。我是从零开始写的，对3D图形没有太多的先验知识。转换完美地工作，在没有zbuffer的情况下进行测试。但是，当启用缓冲区时，它不会按正确的顺序绘制。

以下是它的实现方式。

场景类有一个呈现方法，它在需要更新时由JFrame调用。Render清除zbuffer，然后将命令传递给场景的形状。Renderable是一个接口。守则如下：

public void render(Graphics2D g2, int pitch, int yaw, int roll) 
{
    for(double[] d : buffer)
        Arrays.fill(d, Double.NEGATIVE_INFINITY);
    for(Renderable shape : shapes)
        shape.render(image, pitch, yaw, roll, buffer);
    g2.drawImage(image, null, null);
    for(int x = 0; x < 512; x++)
        for(int y = 0; y < 512; y++)
            image.setRGB(x, y, 0); //Clear buffered image
}

private Renderable[] shapes;
private double[][] buffer = new double[512][512];
private BufferedImage image = new BufferedImage(512, 512, BufferedImage.TYPE_INT_ARGB);

下面是Triangle3D ()中呈现方法的代码。

public void render(BufferedImage image, int pitch, int yaw, int roll, double[][] buffer, boolean showBorders)
{
    Triangle3D rotated = (Triangle3D) getRotated(pitch, yaw, roll);
    rotated.translate(256, 256, 0);
    Polygon path = new Polygon();
    path.addPoint(rotated.getFirst().getFirst().intValue(), rotated.getFirst().getSecond().intValue());
    path.addPoint(rotated.getSecond().getFirst().intValue(), rotated.getSecond().getSecond().intValue());
    path.addPoint(rotated.getThird().getFirst().intValue(), rotated.getThird().getSecond().intValue());

    Rectangle bounds = path.getBounds();
    int minY = Math.max(Math.min(bounds.y, 511), 0);
    int maxY = Math.max(Math.min(bounds.y + bounds.height, 511), 0);
    int minX = Math.max(Math.min(bounds.x, 511), 0);
    int maxX = Math.max(Math.min(bounds.x + bounds.width, 511), 0);

    for (int y = minY; y <= maxY; y++) 
        for (int x = minX; x <= maxX; x++)
            if(path.contains(x, y) && buffer[x][y] < getZ(x, y))
            {
                image.setRGB(x, y, color.getRGB());
                buffer[x][y] = getZ(x, y);
            }
}

public double getZ(int x, int y)
{
    double a = getFirst().getFirst();
    double b = getFirst().getSecond();
    double c = getFirst().getThird();

    double d = getSecond().getFirst();
    double e = getSecond().getSecond();
    double f = getSecond().getThird();

    double g = getThird().getFirst();
    double h = getThird().getSecond();
    double w = getThird().getThird();

    double v1a = d - a;
    double v1b = e - b;
    double v1c = f - c;
    double v2a = g - a;
    double v2b = h - b;
    double v2c = w - c;

    double i = v1b * v2c - v1c * v2b;
    double j = v1c * v2a - v1a * v2c;
    double k = v1a * v2b - v1b * v2a;

    double o = (a * i) + (b * j) + (c * k);

    return ((o - (x * i) - (y * j)) / k);
}

我注意到最后呈现的Triangle3D (场景的shapes[]中的最后一项)是不可见的，即使它应该在前面绘制。

知道为什么不能用吗？

完整代码：https://drive.google.com/folderview?id=0Bw-Cg4sUAOWvS3BTazgyeTRRUjg&usp=sharing

Answer 1

getZ()返回未旋转三角形的Z值。改为rotated.getZ()