glDrawElements

接口定义

void glDrawElements( 
    GLenum mode, // 绘制的类型，如GL_LINE_STRIP,GL_TRIANGLES等
    GLsizei count, // 需要绘制的顶点数
      GLenum type, // 绘制元素的类型（取决于顶点数据的类型）
     const GLvoid * indices // 数据Buffer的Offset指针
    );

简单使用：

//correspond code in shader: layout (location = 2) in vec3 aColor;
GLint vertexColorLocation = 2;

glEnableVertexAttribArray(vertexLocation);   

glVertexAttribPointer(vertexColorLocation,
                          3,
                          GL_FLOAT,
                          GL_FALSE,
                          0,
                          colour);//colour为每个顶点的颜色数组

// indices 为顶点位置数据，36 为顶点数量

glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_SHORT, indices);

glDisableVertexAttribArray(vertexColorLocation);

glDrawArrays

接口定义

void glDrawArrays(    
    GLenum mode,
    GLint first, // 绑定数组（加载到OpenGL）中的元素开始下标
    GLsizei count //读取几个
    );

绘制例子

// 顶点数据格式：
// GLfloat[] = {x1,y1,z1,r1,g1,b1,x2,y2,z2,r2,g2,b2....}
// 顶点颜色Buf
    GLuint vertBuf;
    glGenBuffers(1, &vertBuf);
    glBindBuffer(GL_ARRAY_BUFFER, vertBuf);
    glBufferData(GL_ARRAY_BUFFER,
                 sizeof(cubeVerticesWithColor),
                 cubeVerticesWithColor,
                 GL_STATIC_DRAW);

    // 设置顶点数据属性
    GLint vertexLocation = 0;
    glVertexAttribPointer(
            vertexLocation,
            3,
            GL_FLOAT,
            GL_FALSE,
            sizeof(GLfloat) * 6,//6:x,y,z,r,g,b
            (void *) 0
    );
    glEnableVertexAttribArray(vertexLocation);

    // 设置顶点颜色数据属性
    GLint vertexColorLocation = 2;
    glVertexAttribPointer(vertexColorLocation,
                          3,
                          GL_FLOAT,
                          GL_FALSE,
                          sizeof(GLfloat) * 6,
                          (void *) (sizeof(GLfloat) * 3));

    glEnableVertexAttribArray(vertexColorLocation);

    // 索引Buf
    GLuint vertIndexedBuf;
    glGenBuffers(1, &vertIndexedBuf);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vertIndexedBuf);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);


    // 绘制
    //    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_SHORT, indices);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_SHORT, 0);

    if (EGL_FALSE == eglSwapBuffers(mEglDisplay, mEglSurface)) {
       //error
    }

    glDisableVertexAttribArray(vertexLocation);
    glDisableVertexAttribArray(vertexColorLocation);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glDeleteBuffers(1, &vertBuf);
    glDeleteBuffers(1, &vertIndexedBuf);