Question

人，在GLUT display（）函数中，我将像素读入PACK缓冲区对象。

// Read the frame buffer into the binded read stream.
glBindBuffer(GL_PIXEL_PACK_BUFFER, bufferObject[RetrievingPixelBuffer]);
glReadPixels(0,0,width, height, GL_RGBA, GL_FLOAT, BUFFER_OFFSET(0));

GLfloat* pixels = (GLfloat*) glMapBuffer( GL_PIXEL_PACK_BUFFER, GL_READ_WRITE);
for( int i = 0; i <width*height; i++)
{
    *pixels = 1.0;
    pixels+=4;
}
glUnmapBuffer(GL_PIXEL_PACK_BUFFER);

glDrawPixels(width, height, GL_RGBA,
             GL_FLOAT, BUFFER_OFFSET(0));

我读取并更新像素数据内容，并再次将其绘制到帧缓冲区中。

但glDrawPixels返回GL_invalid_operation。有什么不对吗？

感谢。

Answer 1

如果使用PBO glDrawPixels对GL_UNPACK_BUFFER进行操作。您只有GL_PACK_BUFFER个界限。您需要从包绑定中取消绑定缓冲区对象，然后将其绑定到解包绑定，然后调用glDrawPixels。

用于澄清的EDIT代码

// Read the frame buffer into the binded read stream.
glBindBuffer(GL_PIXEL_PACK_BUFFER, bufferObject[RetrievingPixelBuffer]);
glReadPixels(0,0,width, height, GL_RGBA, GL_FLOAT, BUFFER_OFFSET(0));

GLfloat* pixels = (GLfloat*) glMapBuffer( GL_PIXEL_PACK_BUFFER, GL_READ_WRITE);
for( int i = 0; i <width*height; i++)
{
    *pixels = 1.0;
    pixels+=4;
}
glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0); /* unbind the PBO */

glBindBuffer(GL_PIXEL_UNPACK_BUFFER, bufferObject[RetrievingPixelBuffer]);
          /*          ^^^^^^--- You need to bind your PBO for UNPACKING! */
glDrawPixels(width, height, GL_RGBA, GL_FLOAT, BUFFER_OFFSET(0));
glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

具有PACK像素缓冲区对象的DrawPixels

1 个答案: