OpenGL得到了glOrtho黑色屏幕lwjgl

Question

所以，我做了一个2D平台游戏。我得到了纹理，控制和一切正常，直到我决定让游戏拥有滚动相机。我读过的地方说，使用glOrtho移动和缩放相机，但当我打电话glOrtho我的屏幕变成黑色我知道我做错了什么，但不知道该怎么做。

我的游戏循环之前得到这个：

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 

和我得到这个在游戏循环，使相机跟随玩家：

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); 

但它给了我黑色的屏幕..当我更改第一次调用glOrtho的值时，这很好，但我已经在谷歌上搜索这个概要但找不到任何帮助？

编辑：这里的主类

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

这里的问题是，你不改变矩阵模式切换正投影，据我可以告诉前GL_PROJECTION - 作为你的第二个代码片段呢没有矩阵模式状态改变。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); 

请记住这个代码段将重置变换矩阵，所以任何glTransform（）或glRotate（）调用或glScale（）调用，当然就会失去效果，但由于这是在你的游戏循环开始，并且每运行一次我都会运行，我怀疑这应该不是问题。

Answer 2

你的代码有两个问题：你在做“OpenGL初始化”。为什么？ OpenGL是一个状态机，它不会被初始化。你将OpenGL置于你需要的状态，当你需要的时候。构造函数中的大多数OpenGL调用都是不必要的，并且不起作用。大多数OpenGL的东西只能在渲染函数中完成。

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(); 
}