Java LWJGL: When I call “GL11.glEnd” the polygon disappears?

问题

When I call "GL11.glEnd" the polygon disappears. If I leave that one line "GL11.glEnd" out, then it stays on the screen, but when I put it in, the polygon I was drawing disappears.

package package01;

import org.lwjgl.opengl.GL11;

public class Graph {

    ...


void initGraph(){
    GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); 
    GL11.glClearDepth(1.0); 
    GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
    GL11.glOrtho(-500, 500, -281, 281, -1, 1);
    GL11.glColor3f(0.8f, 0.8f, 1.0f);
    GL11.glBegin(GL11.GL_POLYGON);
        GL11.glVertex3f(-60, 110, 0);   
        GL11.glVertex3f(60, 110, 0);
        GL11.glVertex3f(120, 0, 0);
        GL11.glVertex3f(60, -110, 0);
        GL11.glVertex3f(-60, -110, 0);
        GL11.glVertex3f(-120, 0, 0);
    GL11.glEnd();
    GL11.glFlush();
}
}

And here is the second class if it would help.

package package01;

...

public class DisplayScreen {
Graph g = new Graph();


void start(){
    try {
        Display.setDisplayMode(new DisplayMode(1000,562));
        Display.create();
        GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);

    } catch(LWJGLException e) {
        e.printStackTrace();

    }
    while(!Display.isCloseRequested()){

        Display.update();
        g.initGraph();
    }
    Display.destroy();
}


public static void main(String[] args){

    DisplayScreen ds = new DisplayScreen();
    ds.start();

    }
}

回答1:

remove GL11.glOrtho(-500, 500, -281, 281, -1, 1); from the initGraph() method.

add

glMatrixMode(GL11.GL_PROJECTION);
glLoadIdentity();
GL11.glOrtho(-500, 500, -281, 281, -1, 1);
glMatrixMode(GL11.GL_MODELVIEW);

before the game loop.

update needs to be called after initGraph g.initGraph(); Display.update();

来源：https://stackoverflow.com/questions/8950138/java-lwjgl-when-i-call-gl11-glend-the-polygon-disappears

标签

java

opengl

polygon

lwjgl