OpenGL 使用 glOrtho lwjgl 得到黑屏

Question

所以，我制作了一个 2d 平台游戏。我得到了纹理、控件和一切都很好，直到我决定让游戏有一个滚动相机。我读过某处说使用 glOrtho 移动和缩放相机，但是当我调用 glOrtho 时，我的屏幕变黑了，我知道我做错了什么，但不知道该怎么做。

我在游戏循环之前得到了这个：

glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
glOrtho(0, GAME_WIDTH, GAME_HEIGHT, 0, 1, -1);
glMatrixMode(GL_MODELVIEW);
*enabling texture_2d and others

我在游戏循环中得到了这个，让相机跟随玩家：

glClear(GL_COLOR_BUFFER_BIT);
xOff = player.x - GAME.WIDTH / 2;
yOff = player.y - GAME.HEIGHT / 2;
glOrtho(xOff, xOff + GAME_WIDTH, yOff + GAME_HEIGHT, yOff, 1, -1);

但是它给了我黑屏..虽然我在第一次调用 glOrtho 时更改值很好..我已经在谷歌上搜索了这个问题但找不到任何帮助？

编辑：这是主类

package com.org.Game;

import static org.lwjgl.opengl.GL11.*;

import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;

import com.org.Game.Graphics.Draw;
import com.org.Game.Graphics.Sprite;
import com.org.Game.Graphics.Spritesheet;
import com.org.Game.Level.Level;
import com.org.Game.Level.Entity.Mob.Player;

public class Main {

    private static String title = "Platformer";
    private static int WINDOW_WIDTH = 800, WINDOW_HEIGHT = 600;
    private static int GAME_WIDTH = 320, GAME_HEIGHT = 240;

    private boolean exit = false;
    private long lastFPS;
    private int fps;
    private long lastFrame;
    private long delta;
    private boolean fpscap = true;

    private Level lvl;
    private Player player;
    private int xOff, yOff;

    public Main() {
        try {
            Display.setDisplayMode(new DisplayMode(WINDOW_WIDTH, WINDOW_HEIGHT));
            Display.setTitle(title);
            Display.setVSyncEnabled(true);
            DisplayMode[] modes = Display.getAvailableDisplayModes();
            for (int i = 0; i < modes.length; i++) {
                if (modes[i].getWidth() == WINDOW_WIDTH && modes[i].getHeight() == WINDOW_HEIGHT && modes[i].getFrequency() == 60 && modes[i].isFullscreenCapable()) {
                    Display.setDisplayMode(modes[i]);
                    System.out.println(modes[i].getWidth() + " " + modes[i].getHeight() + " " + modes[i].getBitsPerPixel() + " " + modes[i].getFrequency() + " " + modes[i].isFullscreenCapable());
                    break;
                }
            }
            // Display.setFullscreen(true);
            Display.create();
        } catch (LWJGLException e) {
            e.printStackTrace();
            Display.destroy();
            System.exit(0);
        }

        glLoadIdentity();
        glMatrixMode(GL_PROJECTION);
        glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
        glOrtho(0, GAME_WIDTH, GAME_HEIGHT, 0, 1, -1);
        glMatrixMode(GL_MODELVIEW);

        glEnable(GL_TEXTURE_2D);

        glEnable(GL_CULL_FACE);
        glCullFace(GL_BACK);

        glEnable(GL_BLEND);
        glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_DST_COLOR);

        glPolygonMode(GL_FRONT, GL_FILL);

        lvl = new Level();
        lvl.loadLevel("level0.dat");
        if (lvl == null) System.out.println("NULL");
        player = new Player(16, 16, Sprite.cobalt, lvl);

        start();

        Spritesheet.tiles.tex.release();
        Spritesheet.bg_day.tex.release();
        Display.destroy();
        System.exit(0);
    }

    int a;

    private void render() {
        Draw.clearScreen();

        glLoadIdentity();
        glMatrixMode(GL_PROJECTION);
        glOrtho(xOff, xOff + GAME_WIDTH, yOff + GAME_HEIGHT, yOff, 1, -1);
        glMatrixMode(GL_MODELVIEW);

        glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

        Draw.setTexture(Spritesheet.bg_day);
        Draw.drawBackground(GAME_WIDTH, GAME_HEIGHT, Spritesheet.bg_day);

        Draw.setTexture(Spritesheet.tiles);
        lvl.renderLevel(GAME_WIDTH, GAME_HEIGHT, xOff, yOff);

        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        player.render();
    }

    private void update(long delta) {
        player.update(delta);
        if (Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) exit = true;
        if (Keyboard.isKeyDown(Keyboard.KEY_Z)) fpscap = true;
        if (Keyboard.isKeyDown(Keyboard.KEY_X)) fpscap = false;
    }

    public void start() {
        lastFPS = getTime();
        getDelta();

        while (!Display.isCloseRequested() && !exit) {
            getDelta();

            xOff = (int) player.x - GAME_WIDTH / 2;
            yOff = (int) player.y - GAME_HEIGHT / 2;

            render();
            update(delta);

            updateFPS();
            Display.update();
            if (fpscap) Display.sync(120);
        }
    }

    private void getDelta() {
        long now = getTime();
        delta = now - lastFrame;
        lastFrame = now;
    }

    private void updateFPS() {
        fps++;
        if (getTime() - lastFPS > 1000) {
            lastFPS += 1000;
            Display.setTitle(title + " FPS: " + fps);
            fps = 0;
        }
    }

    private long getTime() {
        return Sys.getTime() * 1000 / Sys.getTimerResolution();
    }

    public static void main(String[] args) {
        new Main();
    }

}

Answer 1

据我所知，这里的问题是，在切换正交投影之前，您没有将矩阵模式更改为 GL_PROJECTION - 因为您的第二个代码 sn-p 没有矩阵模式状态更改。所以，试试这个：

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
xOff = player.x - GAME.WIDTH / 2;
yOff = player.y - GAME.HEIGHT / 2;
glOrtho(xOff, xOff + GAME_WIDTH, yOff + GAME_HEIGHT, yOff, 1, -1);
glMatrixMode(GL_MODELVIEW);

请记住，这段代码 sn-p 将重置您的转换矩阵，因此任何 glTransform() 或 glRotate() 调用或 glScale() 调用当然会被取消，但因为这是在游戏循环的开始，并且运行每个滴答声我怀疑这不应该是一个问题。

Answer 2

您的代码有两个问题：您正在执行“OpenGL 初始化”。为什么？ OpenGL 是一个状态机，它不会被初始化。您将 OpenGL 置于您需要的状态，就在您需要的时候。构造函数中的大部分 OpenGL 调用都是不必要的，并且没有任何效果。大多数 OpenGL 的东西应该只在渲染函数中完成。

对于渲染方法试试这个：

private void render() {
            // glViewport does not depend on the matrix state
    glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);

    Draw.clearScreen();

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(xOff, xOff + GAME_WIDTH, yOff + GAME_HEIGHT, yOff, 1, -1);

    glMatrixMode(GL_MODELVIEW);
            glLoadIdentity();

    glEnable(GL_TEXTURE_2D);

    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);

            // probably don't want to blend the background
            // actually get your blending stuff right, I removed it entirely
            // because it's completely unclear from your code what you want
            // to blend which way
    glDisable(GL_BLEND); 
    Draw.setTexture(Spritesheet.bg_day);
    Draw.drawBackground(GAME_WIDTH, GAME_HEIGHT, Spritesheet.bg_day);

    Draw.setTexture(Spritesheet.tiles);
    lvl.renderLevel(GAME_WIDTH, GAME_HEIGHT, xOff, yOff);

            // probably needs its texture set.
    player.render();
}