6

我对opengl很陌生，我真的不明白这里发生了什么。我正在尝试使用两个 VAO 创建多个对象，并使用自定义矩阵来旋转/平移它们。当我加载一个时图像很好，但是当我加载两个时它们都闪烁。我的初始化是这样的，其中每个缓冲区、顶点位置、顶点索引和顶点颜色都有一个不同的数组。

void init()
{
 readFile();
 //glEnable(GL_DEPTH);
 glEnable( GL_DEPTH_TEST );
 //make background yerpul in colour
 glClearColor( 0.235,  0.194,  0.314, 1.0 );


    // Load shaders and use the resulting shader program
    program = InitShader( "aVertexShader61.glsl", "aFragShader61.glsl" );
    glUseProgram( program );

    // Create a vertex array object
    glGenVertexArrays( 1, &vao );
    glBindVertexArray( vao );

    // Create and initialize two buffer objects
    glGenBuffers( 2, buffers);

    //one buffer for the vertexPositions and colours
    glBindBuffer( GL_ARRAY_BUFFER, buffers[0]);
    glBufferData( GL_ARRAY_BUFFER, numVertexPositionBytes + numVertexColourBytes,NULL, GL_STATIC_DRAW );
    glBufferSubData( GL_ARRAY_BUFFER, 0, numVertexPositionBytes, vertexPositions );
    glBufferSubData( GL_ARRAY_BUFFER, numVertexPositionBytes, numVertexColourBytes, vertexColours);

    //one buffer for the indices
    glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, buffers[1]);
    glBufferData( GL_ELEMENT_ARRAY_BUFFER, numVertexIndexBytes,vertexIndicies, GL_STATIC_DRAW );

    // set up vertex arrays
    GLuint vPosition = glGetAttribLocation( program, "vPosition" );
    glEnableVertexAttribArray( vPosition );
    glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) );

    GLuint vColor = glGetAttribLocation( program, "vColor" );
    glEnableVertexAttribArray( vColor );
    glVertexAttribPointer( vColor, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(numVertexPositionBytes) );

    // Second object

    glGenVertexArrays( 1, &vao2 );
    glBindVertexArray( vao2 );

    glGenBuffers( 2, buffers2);

    //one buffer for the vertexPositions and colours
    glBindBuffer( GL_ARRAY_BUFFER, buffers2[0]);
    glBufferData( GL_ARRAY_BUFFER, numVertexPositionBytes + numVertexColourBytes,NULL, GL_STATIC_DRAW );
    glBufferSubData( GL_ARRAY_BUFFER, 0, numVertexPositionBytes, vertexPositions2 );
    glBufferSubData( GL_ARRAY_BUFFER, numVertexPositionBytes, numVertexColourBytes, vertexColours2);

    //one buffer for the indices
    glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, buffers2[1]);
    glBufferData( GL_ELEMENT_ARRAY_BUFFER, numVertexIndexBytes,vertexIndicies2, GL_STATIC_DRAW );

    // set up vertex arrays
    GLuint vPosition2 = glGetAttribLocation( program, "vPosition" );
    glEnableVertexAttribArray( vPosition2 );
    glVertexAttribPointer( vPosition2, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) );

    GLuint vColor2 = glGetAttribLocation( program, "vColor" );
    glEnableVertexAttribArray( vColor2 );
    glVertexAttribPointer( vColor2, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(numVertexPositionBytes) );


    glBindVertexArray(0);
}

这是我用 glutPostRedisplay() 调用的显示；在我的空闲函数中，没有任何其他调用来自空闲。mStack 是从外部文件创建的矩阵堆栈对象

    void
    display( void )
{

    //clear for first object, generate matrix and apply to object
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    mStack.loadIdentity();
    mStack.translatef(0,yDisplace,0);
    mStack.rotatef(Theta[Yaxis], 0.0,1.0,0.0);
    for (unsigned char i=0; i<NumVertices; i++){
        mStack.transformf(&vertexPositionsInit[i*4],&vertexPositions[i*4]);

    }

    //Apply to second object
    for (unsigned char i=0; i<NumVertices; i++){
        mStack.transformf(&vertexPositionsInit2[i*4],&vertexPositions2[i*4]);

    }


    //Draw first object
    glBindVertexArray(vao);
    glBindBuffer(GL_ARRAY_BUFFER, buffers[0]);
    glBufferSubData(GL_ARRAY_BUFFER, 0, numVertexPositionBytes, vertexPositions );
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers[1]);
    //Indexing into vertices we need to use glDrawElements
    glDrawElements(GL_TRIANGLES, NumIndicies, GL_UNSIGNED_BYTE, 0);
    glutSwapBuffers();


    //Clear and draw second object
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    glutSwapBuffers();
    glBindVertexArray(vao2);
    glBindBuffer(GL_ARRAY_BUFFER, buffers2[0]);
    glBufferSubData(GL_ARRAY_BUFFER, 0, numVertexPositionBytes, vertexPositions2 );
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffers2[1]);
    //Indexing into vertices we need to use glDrawElements
    glDrawElements(GL_TRIANGLES, NumIndicies, GL_UNSIGNED_BYTE, 0);
    glutSwapBuffers();


}

我正在使用简单的顶点和片段着色器。顶点着色器，

in  vec4 vPosition;
in  vec4 vColor;
out vec4 color;

void main() 
{
  gl_Position = vPosition;
  color = vColor;
}

和片段着色器，

in  vec4  color;
out vec4  fColor;

void main() 
{ 
    fColor = color;
}

任何帮助将不胜感激，如果需要，我可以发布 Matrix 文件。谢谢

4

1 回答 1

5

不要在对象之间调用glutSwapBuffers()或调用。glClear()交换缓冲区是一种告诉 GLUT “好的，我已经完成了这一帧，让我们从下一个开始。”

通常你会想要从渲染每个对象的代码中分离出设置和完成每一帧的代码（比如对glClear()和的调用glutSwapBuffers()），因为 OpenGL 基本上是一个巨大的全局变量盒子，很难编写好的 OpenGL 代码无需将您的方法分解成小块。

于 2013-09-07T00:56:28.757 回答