Question

我有一个简短的程序，用于绘制3D GL.GL_QUADS，此处为display()方法 -

public void display(GLAutoDrawable drawable) {
        ....
        gl.glBegin(GL.GL_QUADS); // of the color cube

        // Top-face
        gl.glColor3f(0.0f, 1.0f, 0.0f); // green
        gl.glVertex3f(1.0f, 1.0f, -1.0f);
        gl.glVertex3f(-1.0f, 1.0f, -1.0f);
        gl.glVertex3f(-1.0f, 1.0f, 1.0f);
        gl.glVertex3f(1.0f, 1.0f, 1.0f);

        // Bottom-face
        gl.glColor3f(1.0f, 0.5f, 0.0f); // orange
        gl.glVertex3f(1.0f, -1.0f, 1.0f);
        gl.glVertex3f(-1.0f, -1.0f, 1.0f);
        gl.glVertex3f(-1.0f, -1.0f, -1.0f);
        gl.glVertex3f(1.0f, -1.0f, -1.0f);

        // Front-face
        gl.glColor3f(1.0f, 0.0f, 0.0f); // red
        gl.glVertex3f(1.0f, 1.0f, 1.0f);
        gl.glVertex3f(-1.0f, 1.0f, 1.0f);
        gl.glVertex3f(-1.0f, -1.0f, 1.0f);
        gl.glVertex3f(1.0f, -1.0f, 1.0f);

        // Back-face
        gl.glColor3f(1.0f, 1.0f, 0.0f); // yellow
        gl.glVertex3f(1.0f, -1.0f, -1.0f);
        gl.glVertex3f(-1.0f, -1.0f, -1.0f);
        gl.glVertex3f(-1.0f, 1.0f, -1.0f);
        gl.glVertex3f(1.0f, 1.0f, -1.0f);

        // Left-face
        gl.glColor3f(0.0f, 0.0f, 1.0f); // blue
        gl.glVertex3f(-1.0f, 1.0f, 1.0f);
        gl.glVertex3f(-1.0f, 1.0f, -1.0f);
        gl.glVertex3f(-1.0f, -1.0f, -1.0f);
        gl.glVertex3f(-1.0f, -1.0f, 1.0f);

        // Right-face
        gl.glColor3f(1.0f, 0.0f, 1.0f); // violet
        gl.glVertex3f(1.0f, 1.0f, -1.0f);
        gl.glVertex3f(1.0f, 1.0f, 1.0f);
        gl.glVertex3f(1.0f, -1.0f, 1.0f);
        gl.glVertex3f(1.0f, -1.0f, -1.0f);
            ....
}

现在我想将上面的绘图更改为“Vertex Arrays”模式并获得相同的结果，所以我做了以下内容：

创建了float的所有顶点坐标的GL.GL_QUADS数组。
put此数组为Buffer。
告诉OpenGL顶点在哪里（8个顶点）。
告诉OpenGL要绘制哪些索引。

以下是我编写的主要代码（已编辑） -

public class DisplayWithArray extends GLCanvas implements GLEventListener,
        KeyListener {

    private float[] cubeVertices = { 1.0f, 1.0f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f,
            1.0f, 1.0f, 1.0f, 1.0f, 1.0f,

            1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, 1.0f,
            -1.0f, -1.0f,

            1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f,
            -1.0f, 1.0f,

            1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f, 1.0f,
            1.0f, -1.0f,

            -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f,
            -1.0f, 1.0f,

            1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f,
            -1.0f, -1.0f };

    private float[] colorVertices ={ 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
        1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.5f, 0.0f, 1.0f, 0.5f, 0.0f,
        1.0f, 0.5f, 0.0f, 1.0f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f,
        0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f,
        1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f };

    // 1st edit  - 24 positions of the GL.GL_QUADS
    private int[] indices = new int[24] ;

    private IntBuffer indicesBuf ;  
}
public DisplayWithArray(GLCapabilities capabilities, int width, int height) {
        for (int i=0 ; i<24 ; i++) {
            this.indices[i] = i ; 
    }
public void init(GLAutoDrawable drawable) {
            ...
        final GL gl = drawable.getGL();
            ...
        setupPointer(gl);
}

public void display(GLAutoDrawable drawable) {

        final GL gl = drawable.getGL();
        // draw
        gl.glDrawArrays(GL.GL_QUADS, 0, 24);
}

public void setupPointer(GL gl) {

        FloatBuffer tmpVerticesBuf = BufferUtil
                .newFloatBuffer(cubeVertices.length);
        ;
        FloatBuffer tmpColorVerticesBuf = BufferUtil
                .newFloatBuffer(colorVertices.length);

        for (int i = 0; i < cubeVertices.length; i++) {
            tmpVerticesBuf.put(cubeVertices[i]);
        }
        for (int i = 0; i < colorVertices.length; i++) {
        tmpColorVerticesBuf.put(colorVertices[i]);
    }
        tmpVerticesBuf.rewind();
        tmpColorVerticesBuf.rewind();
        gl.glEnableClientState(GL.GL_VERTEX_ARRAY);
        gl.glVertexPointer(3, GL.GL_FLOAT, 0, tmpVerticesBuf);
        gl.glColorPointer(3, GL.GL_FLOAT, 0, tmpColorVerticesBuf);
        // Indices of polygon
        IntBuffer tmpIndicesBuf = BufferUtil.newIntBuffer(this.indices.length);
        for (int i = 0; i < indices.length; i++) {
            tmpIndicesBuf.put(indices[i]);
        }
        tmpIndicesBuf.rewind();

        indicesBuf = tmpIndicesBuf ; 
}

当我运行它时，我得到一个异常Exception in thread "AWT-EventQueue-0" javax.media.opengl.GLException: glGetError() returned the following error codes after a call to glDrawElements(): GL_INVALID_ENUM at DisplayWithArray.display(DisplayWithArray.java:152)

指向该行 - gl.glDrawElements(GL.GL_QUADS, indices.length, GL.GL_INT, indicesBuf);

这里有什么问题？

修改

根据indices的6面，我将GL.GL_QUADS数组更改为范围[0,5]。并将tmpColorVerticesBuf数组扩展为72个索引（每种颜色4次）。

我仍然有如上所述的相同例外。

编辑2：（现在效果很好）通过比较cubeVertices和colorVertices尺寸（每个阵列72个）和display()使用gl.glDrawArrays(GL.GL_QUADS, 0, 24)（24个3个元素）来解决

Answer 1

错误的是您的阵列大小不同。你的顶点位置数组中有24个vec3，而你的颜色数组只有 6个。因此，当您的索引数组显示“6”时，它将尝试访问包含6个元素的数组中的第7个条目。因此崩溃。

每个数组都使用相同的索引。因此，如果您想要颜色和位置，那么每种颜色必须具有单个对应的位置。反之亦然。你有6种颜色可以使用32个位置。每个属性也不能使用不同的索引。如果您正在进行索引渲染，那么所有必须使用相同的索引。

使用顶点数组绘制3D多边形

1 个答案: