Question

我对opengl很新，我真的不明白这里发生了什么。我正在尝试使用两个VAO来创建多个对象，并使用自定义矩阵来旋转/翻译它们。当我加载一个图像时图像很好，但是当我加载两个图像时它们都闪烁。我的init就是这样，我为每个缓冲区，顶点位置，顶点索引和顶点颜色设置了不同的数组。

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;在我的空闲功能中，没有其他任何来自空闲的调用。 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;
}

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。感谢

Answer 1

不要在对象之间调用glutSwapBuffers()或glClear()。交换缓冲区是告诉GLUT的一种方式“好的，我完成了这个框架，让我们从下一个框架开始。”

通常你会想要从渲染每个对象的代码中拆分出设置和完成每个帧的代码（比如对glClear()和glutSwapBuffers()的调用），因为OpenGL基本上是一个巨大的全局变量框，很难编写好的OpenGL代码而不会将你的方法分成小块。

opengl在渲染多个对象时闪烁

1 个答案: