QGLWidget比QWidget慢 [英] QGLWidget is slower than QWidget

问题描述

问题主要在标题中确定.我尝试了Qt的示例( 2dpainting )并注意到，如果我尝试在QGLWidget上绘图，那么相同的代码会消耗更多的CPU能力，而如果我尝试简单地在QWidget上绘图，则消耗更少的CPU能力.我认为QGLWidget应该更快.还有一个有趣的现象:在QGLWidget中，抗锯齿提示似乎被忽略了.

The problem mainly is determined in the title. I tried out the Qt's example (2dpainting) and noticed, that the same code consumes more CPU power if I try to draw on QGLWidget and less if I try to draw simply on QWidget. I thought that the QGLWidget should be faster. And one more interesting phenomenon: In QGLWidget the antialiasing hint seems to be ignored.

OpenGL版本:3.3.0

OpenGL version: 3.3.0

那为什么呢?

推荐答案

首先，请注意您链接到的文档底部的文本:

Firstly, note this text at the bottom of the documentation that you link to:

该示例显示了在同一时间执行的相同绘制操作 时间在Widget和GLWidget中.渲染的质量和速度 GLWidget取决于对多重采样和 系统的OpenGL驱动程序提供的硬件加速.如果 缺少对这两种方法的支持，驱动程序可能会退回到 可以以质量换取速度的软件渲染器.

The example shows the same painting operations performed at the same time in a Widget and a GLWidget. The quality and speed of rendering in the GLWidget depends on the level of support for multisampling and hardware acceleration that your system's OpenGL driver provides. If support for either of these is lacking, the driver may fall back on a software renderer that may trade quality for speed.

此外，并非总是保证硬件渲染比软件渲染快.这完全取决于要求渲染器执行的操作.

Putting that aside, hardware rendering is not always guaranteed to be faster than software rendering; it all depends upon what the renderer is being asked to do.

如果要渲染的项目的目标不断变化，那么软件可以超越硬件的例子是.因此，如果您有一个绘制程序来绘制一条由不断移动的鼠标创建的线，并且该绘制程序是通过将点添加到每帧绘制的绘制路径上来实现的，则硬件渲染器将不断受到流水线停滞的影响，作为新的点被添加到画家路径.从停顿中建立图形管线需要花费时间，这不是软件渲染器必须处理的事情.

An example of where software can exceed hardware is if the goal of the item being rendered is constantly changing. So, if you have a drawing program that draws a line being created by the mouse being constantly moved and it is implemented by adding points to a painter path that is drawn every frame, a hardware renderer will be subject to constant pipeline stalls as new points are added to the painter path. Setting up the graphics pipeline from a stall takes time, which is not something a software renderer has to deal with.

在您询问的2dPainting示例中，执行绘画调用的helper类正在做很多不必要的工作；保存画家状态；设置笔/刷子；旋转画家；恢复画笔.所有这些在硬件上的开销要大于软件上的开销.要真正看到硬件渲染优于软件，先计算对象在渲染循环(绘画功能)之外的位置，然后不执行任何实际将绘画放置在绘画功能中的操作，这可能会显示出明显的区别.

In the 2dPainting example you ask about, the helper class, which performs the paint calls, is doing a lot of unnecessary work; saving the painter state; setting the pen / brush; rotating the painter; restoring the brush. All of this is a bigger overhead in hardware than software. To really see hardware rendering outperform software, pre-calculating the objects' positions outside of the render loop (paint function) and then doing nothing put actually rendering in the paint function is likely to display a noticeable difference here.

最后，关于抗锯齿，您链接到的文档指出:如果系统的OpenGL驱动程序支持所需的扩展名，则QGLWidget也将使用抗锯齿"

Finally, regarding anti-aliasing, the documentation that you linked to states: "the QGLWidget will also use anti-aliasing if the required extensions are supported by your system's OpenGL driver"

这篇关于QGLWidget比QWidget慢的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！