将OpenGL绘制列表转换为顶点数组或VBO [英] Converting OpenGL draw lists to vertex arrays or VBOs

问题描述

我正在尝试使用在OpenGL 3.0+中已弃用的绘制列表转换程序，以使用顶点数组或VBO，但是我没有找到任何进行转换的示例.

I'm trying to convert a program using draw lists, which are deprecated in OpenGL 3.0+, to use either vertex arrays or VBOs, but I'm not finding any examples of how to do the conversion.

现在程序中是什么(可能是Python，但我真正感兴趣的是适当的OpenGL调用-例如，它也可能是C ++):

What's in the program now is this (happens to be Python, but really what I'm interested in is the appropriate OpenGL calls---it could just as well be C++, for example):

dl = glGenLists(1)
glNewList(dl, GL_COMPILE)
glBindTexture(GL_TEXTURE_2D, texture)
glBegin(GL_QUADS)
glTexCoord2f(0, 0)
glVertex2f(0, 0)
glTexCoord2f(0, 1)
glVertex2f(0, height)
glTexCoord2f(1, 1)
glVertex2f(width, height)
glTexCoord2f(1, 0)
glVertex2f(width, 0)
glEnd()
glEndList()

我们正在将纹理映射到矩形上.然后，我们将其绘制到某处:

We're mapping a texture onto a rectangle. Then later we're drawing it somewhere:

glCallList(dl)

如何将其转换为使用顶点数组? VBO?

How do I convert this to use vertex arrays? VBOs?

推荐答案

下面是一些Java代码，在C中，FloatBuffers将是数组.

Here's some Java code, in C the FloatBuffers would be arrays.

public VBO createVBO(List<Vec2> vertexList, List<Vec2> texelList){
    FloatBuffer vertexBuffer = FloatBuffer.allocate(vertexList.size()*3);
    FloatBuffer texelBuffer = FloatBuffer.allocate(texelList.size()*2);
    for(Vec2 point : vertexList){
        vertexBuffer.put(point.x);
        vertexBuffer.put(point.y);
        vertexBuffer.put(0);
    }
    vertexBuffer.flip();
    for(Vec2 point : texelList){
        texelBuffer.put(point.x);
        texelBuffer.put(point.y);
    }
    texelBuffer.flip();

    int[] vbo = new int[2];
    gl.glGenBuffers(1, vbo, 0);
    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo[0]);
    gl.glBufferData(GL.GL_ARRAY_BUFFER, vertexBuffer.capacity()*4, vertexBuffer, GL2.GL_STATIC_DRAW);
    gl.glGenBuffers(1, vbo, 1);
    gl.glBindBuffer(GL2.GL_ARRAY_BUFFER, vbo[1]);
    gl.glBufferData(GL.GL_ARRAY_BUFFER, texelBuffer.capacity()*4, texelBuffer, GL2.GL_STATIC_DRAW);

    return new VBO(vbo[0], vbo[1], vertexList.size());
}

public void renderVBO(VBO vbo){
    gl.glEnableClientState(GL2.GL_VERTEX_ARRAY);
    gl.glEnableClientState(GL2.GL_TEXTURE_COORD_ARRAY);

    gl.glBindBuffer(GL.GL_ARRAY_BUFFER, vbo.vertices);
    gl.glVertexPointer(3, GL.GL_FLOAT, 0, 0);    
    gl.glBindBuffer(GL.GL_ARRAY_BUFFER, vbo.texels);
    gl.glTexCoordPointer(2, GL.GL_FLOAT, 0, 0);

    gl.glDrawArrays(GL.GL_TRIANGLE_FAN, 0, vbo.length);

    gl.glDisableClientState(GL2.GL_VERTEX_ARRAY);
    gl.glDisableClientState(GL2.GL_TEXTURE_COORD_ARRAY);
}

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