Java OpenGL屏幕大小的纹理映射四边形 [英] Java OpenGL screen sized texture mapped quad

问题描述

我有一个Java OpenGL(JOGL)应用程序，我正在尝试创建一个覆盖整个屏幕的纹理映射的四边形.在绘制一些像素到缓冲区后，我想将这些像素读入纹理并在屏幕上重画它们(应用片段着色器).我将纹理映射到视口的代码是:

I have a Java OpenGL (JOGL) app, and I'm trying to create a texture mapped quad that covers the entire screen. In draw some pixels to a buffer and then I want to read those pixels into a texture and redraw them on screen (with a fragment shader applied). My code for mapping the texture to the viewport is:

        gl.glMatrixMode(GL.GL_PROJECTION);                                        
        gl.glPushMatrix();                                                 
        gl.glLoadIdentity();                                               
        gl.glOrtho( 0, width, height, 0, -1, 1 );                          
        gl.glMatrixMode(GL.GL_MODELVIEW);                                  
        gl.glPushMatrix();                                                 
        gl.glLoadIdentity();
        IntBuffer ib = IntBuffer.allocate(1);
        gl.glEnable(GL.GL_TEXTURE_2D);
        gl.glGenTextures(1, ib);
        gl.glPixelStorei(GL.GL_PACK_ALIGNMENT, 1);
        //buff contains pixels read from glReadPixels
        gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, width, height, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, buff);
        gl.glBindTexture(GL.GL_TEXTURE_2D, ib.get(0));
        gl.glBegin(GL.GL_QUADS);
        gl.glTexCoord2f(0,1);
        gl.glVertex2f(0,0); 
        gl.glTexCoord2f(0,0);
        gl.glVertex2f(0,height);
        gl.glTexCoord2f(1,0);   
        gl.glVertex2f(width,height);
        gl.glTexCoord2f(1,1);      
        gl.glVertex2f(width,0);
        gl.glEnd();
        gl.glBindTexture(GL.GL_TEXTURE_2D, 0);
        gl.glPopMatrix();
        gl.glPopMatrix();

最终结果是一个四边形没有覆盖整个视口(部分打开)，并且不包含缓冲区中的像素.我在这里做错了什么?

The end result is a quad that is not covering the whole viewport (it's partially on) and that does not contain the pixels from the buffer. What am I doing incorrectly here?

谢谢， 杰夫

推荐答案

首先，您只应在初始化代码中创建纹理.您不应该每帧都调用glTexImage2D.如果纹理的大小发生变化，则仅再次调用glTexImage2D；否则，将重新调用. glTexSubImage2D可用于将数据上传到纹理.将glTexImage2D视为新"，而将glTexSubImage2D视为内存副本.

First, you should only create the texture in your initialization code. You should not be calling glTexImage2D every frame. Only call glTexImage2D again if the size of the texture changes; glTexSubImage2D can be used to upload data to the texture. Think of glTexImage2D as "new", while glTexSubImage2D as a memory copy.

在初始化OpenGL之后执行一次.

Do this once, after initializing OpenGL.

IntBuffer ib = IntBuffer.allocate(1);  //Store this in your object
gl.glGenTextures(1, ib);
gl.glPixelStorei(GL.GL_PACK_ALIGNMENT, 1);
//buff contains pixels read from glReadPixels
gl.glBindTexture(GL.GL_TEXTURE_2D, ib.get(0));
gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGBA, width, height, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, 0);
gl.glBindTexture(GL.GL_TEXTURE_2D, 0);

然后，每帧执行一次:

gl.glMatrixMode(GL.GL_PROJECTION);                                        
gl.glPushMatrix();                                                 
gl.glLoadIdentity();                                               
gl.glMatrixMode(GL.GL_MODELVIEW);                                  
gl.glPushMatrix();                                                 
gl.glLoadIdentity();

gl.glBindTexture(GL.GL_TEXTURE_2D, ib.get(0));  //Retrieved from your object
gl.glEnable(GL.GL_TEXTURE_2D);
gl.glTexSubImage2D(GL.GL_TEXTURE_2D, 0, 0, 0, width, height, 0, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, buff);

gl.glBegin(GL.GL_QUADS);
    gl.glTexCoord2f(0,1);
    gl.glVertex2f(-1, -1); 
    gl.glTexCoord2f(0, 0);
    gl.glVertex2f(-1, 1);
    gl.glTexCoord2f(1, 0);   
    gl.glVertex2f(1, 1);
    gl.glTexCoord2f(1, 1);      
    gl.glVertex2f(1, -1);
gl.glEnd();

gl.glMatrixMode(GL.GL_MODELVIEW);                                  
gl.glPopMatrix();   
gl.glMatrixMode(GL.GL_PROJECTION);                                        
gl.glPopMatrix();   
gl.glMatrixMode(GL.GL_MODELVIEW);                                  

通过使用标识进行投影和模型查看，我们可以直接在剪辑空间中提供顶点坐标.剪辑空间中的[-1，1]范围映射到窗口空间中的[0，width/height].因此，我们不必知道或不在乎窗户有多大.只要正确设置了glViewport，它就可以正常工作.

By using identity for projection and modelview, we are able to supply vertex coordinates directly in clip-space. The [-1, 1] range in clip-space maps to [0, width/height] in window space. So we don't have to know or care about how big the window is; as long as the glViewport was set up correctly, this should work.

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