java - SWING 有时比 openGL 更快

Question

我想弄清楚 openGL(LWJGL) 和 swing 在渲染简单正方形时有什么区别。不出所料，openGL 获胜，但在某些测试中结果很接近，甚至支持 swing。为什么会这样？

我的测试结果:

Testing for a total of 500000 rectangles
Swing time: 0.16367821
OpenGL time: 0.06317429
OpenGL relative to SWING is faster by  159.0899%

Testing for a total of 750000 rectangles
OpenGL time: 0.066062525
Swing time: 0.16988374
OpenGL relative to SWING is faster by  157.156%

Testing for a total of 1000000 rectangles
OpenGL time: 0.0907693
Swing time: 0.15694521
OpenGL relative to SWING is faster by  72.90561%

Testing for a total of 1250000 rectangles
OpenGL time: 0.09591239
Swing time: 0.17011923
OpenGL relative to SWING is faster by  77.369385%

Testing for a total of 1500000 rectangles
OpenGL time: 0.11926948
Swing time: 0.21623997
OpenGL relative to SWING is faster by  81.303696%

Testing for a total of 1750000 rectangles
OpenGL time: 0.16327758
Swing time: 0.25741237
OpenGL relative to SWING is faster by  57.65323%

Testing for a total of 2000000 rectangles
OpenGL time: 0.17265266
Swing time: 0.2788536
OpenGL relative to SWING is faster by  61.511322%

Testing for a total of 2250000 rectangles
OpenGL time: 0.2492242
Swing time: 0.3022127
OpenGL relative to SWING is faster by  21.261368%

Testing for a total of 2500000 rectangles
Swing time: 0.3231118
OpenGL time: 0.29499054
OpenGL relative to SWING is faster by  9.532944%

Testing for a total of 2750000 rectangles
OpenGL time: 0.34329778
Swing time: 0.38381234
OpenGL relative to SWING is faster by  11.801575%

Testing for a total of 3000000 rectangles
OpenGL time: 0.34859535
Swing time: 0.39274055
OpenGL relative to SWING is faster by  12.663734%

Testing for a total of 3250000 rectangles
Swing time: 0.4241282
OpenGL time: 0.44056854
OpenGL relative to SWING is faster by  -3.7316208%

Testing for a total of 3500000 rectangles
Swing time: 0.4600469
OpenGL time: 0.4737318
OpenGL relative to SWING is faster by  -2.8887482%

Testing for a total of 3750000 rectangles
Swing time: 0.40855232
OpenGL time: 0.25052726
OpenGL relative to SWING is faster by  63.07698%

Testing for a total of 4000000 rectangles
Swing time: 0.5119725
OpenGL time: 0.55266017
OpenGL relative to SWING is faster by  -7.362152%

Testing for a total of 4250000 rectangles
OpenGL time: 0.5010328
Swing time: 0.57198834
OpenGL relative to SWING is faster by  14.16185%

Testing for a total of 4500000 rectangles
OpenGL time: 0.53123826
Swing time: 0.5992712
OpenGL relative to SWING is faster by  12.806473%

Testing for a total of 4750000 rectangles
OpenGL time: 0.5412617
Swing time: 0.6458795
OpenGL relative to SWING is faster by  19.328514%

Testing for a total of 5000000 rectangles
OpenGL time: 0.58324844
Swing time: 0.69343716
OpenGL relative to SWING is faster by  18.892242%

我使用的代码:

package swingVSopengl;

import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import static org.lwjgl.opengl.GL11.*;

public class SwingVsOpenGL {

    static int amount = 0;
    static float swingtime, opengltime;

    public static void main(String[] args) {

        for (amount = 500000; amount <= 5000000; amount += 250000) {

            System.out.println("Testing for a total of "
                    + String.valueOf(amount) + " rectangles");
            new SwingWay();
            new OpenGLWay();
            System.out.println("OpenGL relative to SWING is faster by  "
                    + String.valueOf(swingtime / opengltime * 100 - 100) + "%");
            System.out.println();
        }

        System.exit(0);
    }

    private static class SwingWay extends JFrame {

        public SwingWay() {
            setSize(64, 64);
            add(new JPanel() {
                @Override
                public void paint(Graphics g) {
                    super.paint(g);
                    long time = System.nanoTime();
                    for (int i = 0; i < amount; i++) {
                        g.fillRect(0, 0, 16, 16);
                    }
                    swingtime = (float) (System.nanoTime() - time) / 1000000000;
                    System.out.print("Swing time: ");
                    System.out.println(swingtime);
                    dispose();
                }
            });
            setVisible(true);
        }

    }

    private static class OpenGLWay {
        OpenGLWay() {
            try {
                Display.setDisplayMode(new DisplayMode(64, 64));
                Display.setTitle("A fresh display!");
                Display.create();
            } catch (LWJGLException e) {
                e.printStackTrace();
                Display.destroy();
                System.exit(1);
            }

            glMatrixMode(GL_PROJECTION);
            glOrtho(0, 640, 480, 0, 1, -1);
            glMatrixMode(GL_MODELVIEW);

            long time = System.nanoTime();
            for (int i = 0; i < amount; i++) {
                glBegin(GL_QUADS);
                glVertex2i(0, 0);
                glVertex2i(16, 0);
                glVertex2i(16, 16);
                glVertex2i(0, 16);
                glEnd();
            }
            opengltime = (float) (System.nanoTime() - time) / 1000000000;
            System.out.print("OpenGL time: ");
            System.out.println(opengltime);

            Display.destroy();
        }
    }

}

Answer 1

渲染单个正方形并不是很困难。本质上，它可以归结为对一段内存进行窗口化并用特定值填充它。

此外，您使用 OpenGL 的方式也会遭受大量开销。您测量的不是 SWING 与 OpenGL 的效率，而是函数调用的效率。抛弃 glBegin ... glEnd (它们已经过时了 15 年多了)并使用顶点数组。也不要通过用勺子喂绘图命令来让 GPU 挨饿。相反，通过每个绘图批处理至少包含 100 个图元的顶点数组为其提供无限量的食物。只有这样你才能离开高空土地。