1. 技术文章
  2. Can not draw anything after text rendering initialization code in lwjgl (Java)

Can not draw anything after text rendering initialization code in lwjgl (Java)

由 ぃ、小莉子 提交于 2019-12-25 06:55:48

问题


Hello I have two seperate initialization codes to switch between rendering 2d shapes and (2d) text in lwjgl. If the initialization code for rendering text is executed, the 2d shapes will not be drawn. I tried everything, and I found the problem line: GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

After I have done something with the glBlendFunc, I can only render tekst, and switching to the initialization code for rendering 2d shapes won't work anymore.

Here are my 2 codes:

Simple 2d rendering:

GL11.glEnable(GL_BLEND);
GL11.glMatrixMode(GL_PROJECTION);
GL11.glLoadIdentity();
GL11.glOrtho(0, Display.getWidth(), Display.getHeight(), 0, 1, -1);

GL11.glMatrixMode(GL_MODELVIEW);
GL11.glLoadIdentity();

Code for rendering text:

GL11.glEnable(GL11.GL_TEXTURE_2D);
GL11.glShadeModel(GL11.GL_SMOOTH);
GL11.glDisable(GL11.GL_DEPTH_TEST);
GL11.glDisable(GL11.GL_LIGHTING);

GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
GL11.glClearDepth(1);

GL11.glEnable(GL11.GL_BLEND);

// Problem line
GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

GL11.glViewport(0,0, 800, 600);
GL11.glMatrixMode(GL11.GL_MODELVIEW);

GL11.glMatrixMode(GL11.GL_PROJECTION);
GL11.glLoadIdentity();
GL11.glOrtho(0, 800, 600, 0, 1, -1);
GL11.glMatrixMode(GL11.GL_MODELVIEW);

I think the problem is just a wrong OpenGl state, but how can I put the states right?


回答1:


It's hard to find out the issue without access to your whole code, thus I can just post some guesses:

  1. Do you clear the colour and depth buffer (glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);)?
  2. Do you enable GL_TEXTURE_2D when drawing textures and disable it otherwise?

I use the same blend function and can draw images just fine (it's the most used blend function for drawing images that have transparency).

PS: This are the only settings I use to draw any kind of 2D stuff (I'm using vertex array objects and shaders for rendering though):

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

    glEnable(GL_MULTISAMPLE);

    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);

    glDisable(GL_DEPTH_TEST);



回答2:


Here is more code

Renderer.java

package game;

import static org.lwjgl.opengl.GL11.GL_BLEND;
import static org.lwjgl.opengl.GL11.GL_COLOR_BUFFER_BIT;
import static org.lwjgl.opengl.GL11.GL_DEPTH_BUFFER_BIT;
import static org.lwjgl.opengl.GL11.GL_DEPTH_TEST;
import static org.lwjgl.opengl.GL11.GL_MODELVIEW;
import static org.lwjgl.opengl.GL11.GL_PROJECTION;
import static org.lwjgl.opengl.GL11.GL_TEXTURE_2D;
import static org.lwjgl.opengl.GL11.glClear;
import static org.lwjgl.opengl.GL11.glEnable;
import static org.lwjgl.opengl.GL11.glLoadIdentity;
import static org.lwjgl.opengl.GL11.glMatrixMode;
import static org.lwjgl.util.glu.GLU.gluPerspective;
import static org.lwjgl.opengl.GL11.GL_CONSTANT_COLOR;
import static org.lwjgl.opengl.GL11.GL_ONE;

import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.GL11;

public class Renderer {

    private static boolean in3d = false;

    public static void initText2D() {

        in3d = false;

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glLoadIdentity();

        //GL11.glEnable(GL11.GL_TEXTURE_2D);
        GL11.glShadeModel(GL11.GL_SMOOTH);
        GL11.glDisable(GL11.GL_DEPTH_TEST);
        GL11.glDisable(GL11.GL_LIGHTING);

        GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        GL11.glClearDepth(1);

        GL11.glEnable(GL11.GL_BLEND);
        GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

        GL11.glViewport(0,0, 800, 600);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);

        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, 800, 600, 0, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
    }

    public static void init2D() {

        in3d = false;

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glLoadIdentity();

        GL11.glEnable(GL_BLEND);
        GL11.glMatrixMode(GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, Display.getWidth(), Display.getHeight(), 0, 1, -1);

        GL11.glMatrixMode(GL_MODELVIEW);
        GL11.glLoadIdentity();

        GL11.glDisable(GL_TEXTURE_2D);

        // Test
        //GL11.glBlendFunc(GL_CONSTANT_COLOR, GL_ONE);

    }

    public static void init3D(float fov, float aspect, float near, float far) {

        in3d = true;

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(fov, aspect, near, far);
        GL11.glMatrixMode(GL_MODELVIEW);

        glEnable(GL_DEPTH_TEST);
        glEnable(GL_TEXTURE_2D);

    }

    public static void begin(int shape) {

        GL11.glBegin(shape);
    }

    public static void end() {

        GL11.glEnd();
    }

    public static void setVertex3(float x, float y, float z) {

        if(!in3d) {

            System.out.println("[WARNING] > Adding 3d vertex but there is no 3d context");
        }

        GL11.glVertex3f(x, y, z);
    }

    public static void setColor(float r, float g, float b) {

        GL11.glColor3f(r, g, b);
    }

    public static void setVertex2(float x, float y) {

        if(in3d) {

            System.out.println("[WARNING] > Adding 2d vertex while in 3d context");
        }

        GL11.glVertex2f(x, y);

    }
}

Button.java (example of how I draw a button in lwjgl)

package gui;
import static org.lwjgl.opengl.GL11.GL_QUADS;
import static org.lwjgl.opengl.GL11.glBegin;
import static org.lwjgl.opengl.GL11.glEnd;
import static org.lwjgl.opengl.GL11.glVertex2f;
import game.Renderer;
import game.TextRenderer;
import org.lwjgl.opengl.GL11;
public class Button extends AbstractButton {

    private String text;

    public Button(int x, int y, int w, int h, String text) {

        this.setX(x);
        this.setY(y);
        this.setWidth(w);
        this.setHeight(h);
        this.text = text;

        paintElement();
    }

    public Button(String text) {

        this.text = text;
        paintElement();
    }

    public Button() {

        paintElement();
    }

    public void paintElement() {

        Renderer.init2D();

        Renderer.begin(GL11.GL_QUADS);

        Renderer.setColor(this.getColorR(), this.getColorG(), this.getColorB());

        Renderer.setVertex2(this.getX(), this.getY());
        Renderer.setVertex2(this.getX() + this.getWidth(), this.getY());
        Renderer.setVertex2(this.getX() + this.getWidth(), this.getY() + this.getHeight());
        Renderer.setVertex2(this.getX(), this.getY() + this.getHeight());

        Renderer.end();

        Renderer.initText2D();
        TextRenderer.drawString(this.getX() + 10, this.getY() + 10, this.text);
    }

}

Main.java

package game;

import static org.lwjgl.opengl.GL11.GL_COLOR_BUFFER_BIT;
import static org.lwjgl.opengl.GL11.GL_DEPTH_BUFFER_BIT;
import static org.lwjgl.opengl.GL11.GL_QUADS;
import static org.lwjgl.opengl.GL11.glBegin;
import static org.lwjgl.opengl.GL11.glClear;
import static org.lwjgl.opengl.GL11.glColor3f;
import static org.lwjgl.opengl.GL11.glEnd;
import static org.lwjgl.opengl.GL11.glLoadIdentity;
import static org.lwjgl.opengl.GL11.glMatrixMode;
import static org.lwjgl.opengl.GL11.glOrtho;
import static org.lwjgl.opengl.GL11.glVertex2f;

import java.awt.Font;

import gui.Button;

import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.newdawn.slick.Color;
import org.newdawn.slick.TrueTypeFont;

public class Main {

    private int gamestate;
    private boolean closeRequested;

    private static Camera cam;
    private static User user;

    public Main() {

        createUser();
        createDisplay();
        createCamera();
        gameLoop();
        cleanUp();
    }

    private void createUser() {


    }

    private void createDisplay() {

        try {

            Display.setDisplayMode(new DisplayMode(800, 600));
            Display.setResizable(true);
            Display.create();


        } catch (LWJGLException e) {

            e.printStackTrace();
        }
    }

    private void createCamera() {


    }

    private void gameLoop() {

        while(!closeRequested) {

            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            glLoadIdentity();

            //Renderer.init2D();
            /*
            // Test 2d line
            Renderer.init2D();
            Renderer.setColor(1.0f,  1.0f,  1.0f);
            Renderer.begin(GL11.GL_LINE);
            Renderer.setVertex2(0, 0);
            Renderer.setVertex2(100, 100);
            Renderer.end();
            */

            // set the color of the quad (R,G,B,A)
            glColor3f(0.7f, 0.5f, 1.0f);

            // draw quad
            glBegin(GL_QUADS);
                glVertex2f(100,100);
                glVertex2f(100+200,100);
                glVertex2f(100+200,100+200);
                glVertex2f(100,100+200);
            glEnd();

            checkInput();

            Button b = new Button(100, 100, 100, 30, "Test");

            Display.update();
            Display.sync(10);
        }

        return;
    }

    private void checkInput() {

        // Check keyboard, mouse and other input

        if(Display.isCloseRequested()) {

            closeRequested = true;
        }

        return;
    }

    private void cleanUp() {


    }

    public static void main(String[] args) {

        new Main();
    }
}



回答3:


I got it working!

This is my new (working) code:

init2d

GL11.glEnable(GL_BLEND);
GL11.glMatrixMode(GL_PROJECTION);
GL11.glLoadIdentity();
GL11.glOrtho(0, Display.getWidth(), Display.getHeight(), 0, 1, -1);
GL11.glMatrixMode(GL_MODELVIEW);
GL11.glLoadIdentity();

// solution
GL11.glBindTexture(GL11.GL_TEXTURE_2D, 0);

initText2d

GL11.glEnable(GL11.GL_TEXTURE_2D);
GL11.glShadeModel(GL11.GL_SMOOTH);
GL11.glDisable(GL11.GL_DEPTH_TEST);
GL11.glDisable(GL11.GL_LIGHTING);

GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
GL11.glClearDepth(1);

GL11.glEnable(GL11.GL_BLEND);
GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

GL11.glViewport(0,0, 800, 600);
GL11.glMatrixMode(GL11.GL_MODELVIEW);

GL11.glMatrixMode(GL11.GL_PROJECTION);
GL11.glLoadIdentity();
GL11.glOrtho(0, 800, 600, 0, 1, -1);
GL11.glMatrixMode(GL11.GL_MODELVIEW);

I think the problem was that slick uses textures for text rendering, and I had to enable the textures or bind them to 0. See this: http://lwjgl.org/forum/index.php?topic=4019.0



来源：https://stackoverflow.com/questions/21336837/can-not-draw-anything-after-text-rendering-initialization-code-in-lwjgl-java

标签
java
opengl
rendering
lwjgl
易学教程内所有资源均来自网络或用户发布的内容，如有违反法律规定的内容欢迎反馈！
该文章没有解决你所遇到的问题?点击提问,说说你的问题,让更多的人一起探讨吧!