<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- hellovulkanwindow.qdoc --> <title>Hello Vulkan Window Example | Qt GUI 5.12.2</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.12</td><td ><a href="qtgui-index.html">Qt GUI</a></td><td >Hello Vulkan Window Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtgui-index.html">Qt 5.12.2 Reference Documentation</a></td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#startup">Startup</a></li> <li class="level1"><a href="#the-qvulkanwindow-subclass">The QVulkanWindow Subclass</a></li> <li class="level1"><a href="#the-actual-rendering">The Actual Rendering</a></li> <li class="level1"><a href="#running-the-example">Running the Example</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Hello Vulkan Window Example</h1> <span class="subtitle"></span> <!-- $$$hellovulkanwindow-brief --> <p>Shows the basics of using <a href="qvulkanwindow.html">QVulkanWindow</a>.</p> <!-- @@@hellovulkanwindow --> <!-- $$$hellovulkanwindow-description --> <div class="descr"> <a name="details"></a> <p>The <i>Hello Vulkan Window Example</i> shows the basics of using <a href="qvulkanwindow.html">QVulkanWindow</a> in order to display rendering with the Vulkan graphics API on systems that support this.</p> <p class="centerAlign"><img src="images/hellovulkanwindow.png" alt="" /></p><p>In this example there will be no actual rendering: it simply begins and ends a render pass, which results in clearing the buffers to a fixed value. The color buffer clear value changes on every frame.</p> <a name="startup"></a> <h2 id="startup">Startup</h2> <p>Each Qt application using Vulkan will have to have a <code>Vulkan instance</code> which encapsulates application-level state and initializes a Vulkan library.</p> <p>A <a href="qvulkanwindow.html">QVulkanWindow</a> must always be associated with a <a href="qvulkaninstance.html">QVulkanInstance</a> and hence the example performs instance creation before the window. The <a href="qvulkaninstance.html">QVulkanInstance</a> object must also outlive the window.</p> <pre class="cpp"> <span class="type"><a href="qvulkaninstance.html">QVulkanInstance</a></span> inst; <span class="preprocessor">#ifndef Q_OS_ANDROID</span> inst<span class="operator">.</span>setLayers(<span class="type"><a href="../qtcore/qbytearraylist.html">QByteArrayList</a></span>() <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_standard_validation"</span>); <span class="preprocessor">#else</span> inst<span class="operator">.</span>setLayers(<span class="type"><a href="../qtcore/qbytearraylist.html">QByteArrayList</a></span>() <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_GOOGLE_threading"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_parameter_validation"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_object_tracker"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_core_validation"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_image"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_LUNARG_swapchain"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"VK_LAYER_GOOGLE_unique_objects"</span>); <span class="preprocessor">#endif</span> <span class="keyword">if</span> (<span class="operator">!</span>inst<span class="operator">.</span>create()) <a href="../qtcore/qtglobal.html#qFatal">qFatal</a>(<span class="string">"Failed to create Vulkan instance: %d"</span><span class="operator">,</span> inst<span class="operator">.</span>errorCode()); </pre> <p>The example enables validation layers, when supported. When the requested layers are not present, the request will be ignored. Additional layers and extensions can be enabled in a similar manner.</p> <pre class="cpp"> VulkanWindow w; w<span class="operator">.</span>setVulkanInstance(<span class="operator">&</span>inst); w<span class="operator">.</span>resize(<span class="number">1024</span><span class="operator">,</span> <span class="number">768</span>); w<span class="operator">.</span>show(); </pre> <p>Once the instance is ready, it is time to create a window. Note that <code>w</code> lives on the stack and is declared after <code>inst</code>.</p> <a name="the-qvulkanwindow-subclass"></a> <h2 id="the-qvulkanwindow-subclass">The QVulkanWindow Subclass</h2> <p>To add custom functionality to a <a href="qvulkanwindow.html">QVulkanWindow</a>, subclassing is used. This follows the existing patterns from <a href="qopenglwindow.html">QOpenGLWindow</a> and <a href="../qtwidgets/qopenglwidget.html">QOpenGLWidget</a>. However, <a href="qvulkanwindow.html">QVulkanWindow</a> utilizes a separate <a href="qvulkanwindowrenderer.html">QVulkanWindowRenderer</a> object. This resembles QQuickFramebufferObject, and allows better separation of the functions that are supposed to be reimplemented.</p> <pre class="cpp"> <span class="keyword">class</span> VulkanRenderer : <span class="keyword">public</span> <span class="type"><a href="qvulkanwindowrenderer.html">QVulkanWindowRenderer</a></span> { <span class="keyword">public</span>: VulkanRenderer(<span class="type"><a href="qvulkanwindow.html">QVulkanWindow</a></span> <span class="operator">*</span>w); <span class="type">void</span> initResources() override; <span class="type">void</span> initSwapChainResources() override; <span class="type">void</span> releaseSwapChainResources() override; <span class="type">void</span> releaseResources() override; <span class="type">void</span> startNextFrame() override; <span class="keyword">private</span>: <span class="type"><a href="qvulkanwindow.html">QVulkanWindow</a></span> <span class="operator">*</span>m_window; <span class="type"><a href="qvulkandevicefunctions.html">QVulkanDeviceFunctions</a></span> <span class="operator">*</span>m_devFuncs; <span class="type">float</span> m_green <span class="operator">=</span> <span class="number">0</span>; }; <span class="keyword">class</span> VulkanWindow : <span class="keyword">public</span> <span class="type"><a href="qvulkanwindow.html">QVulkanWindow</a></span> { <span class="keyword">public</span>: <span class="type"><a href="qvulkanwindowrenderer.html">QVulkanWindowRenderer</a></span> <span class="operator">*</span>createRenderer() override; }; </pre> <p>The <a href="qvulkanwindow.html">QVulkanWindow</a> subclass reimplements the factory function <a href="qvulkanwindow.html#createRenderer">QVulkanWindow::createRenderer</a>(). This simply returns a new instance of the <a href="qvulkanwindowrenderer.html">QVulkanWindowRenderer</a> subclass. In order to be able to access various Vulkan resources via the window object, a pointer to the window is passed and stored via the constructor.</p> <pre class="cpp"> <span class="type"><a href="qvulkanwindowrenderer.html">QVulkanWindowRenderer</a></span> <span class="operator">*</span>VulkanWindow<span class="operator">::</span>createRenderer() { <span class="keyword">return</span> <span class="keyword">new</span> VulkanRenderer(<span class="keyword">this</span>); } VulkanRenderer<span class="operator">::</span>VulkanRenderer(<span class="type"><a href="qvulkanwindow.html">QVulkanWindow</a></span> <span class="operator">*</span>w) : m_window(w) { } </pre> <p>Graphics resource creation and destruction is typically done in one of the init - resource functions.</p> <pre class="cpp"> <span class="type">void</span> VulkanRenderer<span class="operator">::</span>initResources() { <a href="../qtcore/qtglobal.html#qDebug">qDebug</a>(<span class="string">"initResources"</span>); m_devFuncs <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">></span>vulkanInstance()<span class="operator">-</span><span class="operator">></span>deviceFunctions(m_window<span class="operator">-</span><span class="operator">></span>device()); } </pre> <a name="the-actual-rendering"></a> <h2 id="the-actual-rendering">The Actual Rendering</h2> <p><a href="qvulkanwindow.html">QVulkanWindow</a> subclasses queue their draw calls in their reimplementation of <a href="qvulkanwindowrenderer.html#startNextFrame">QVulkanWindowRenderer::startNextFrame</a>(). Once done, they are required to call back <a href="qvulkanwindow.html#frameReady">QVulkanWindow::frameReady</a>(). The example has no asynchronous command generation, so the frameReady() call is made directly from startNextFrame().</p> <pre class="cpp"> <span class="type">void</span> VulkanRenderer<span class="operator">::</span>startNextFrame() { m_green <span class="operator">+</span><span class="operator">=</span> <span class="number">0.005f</span>; <span class="keyword">if</span> (m_green <span class="operator">></span> <span class="number">1.0f</span>) m_green <span class="operator">=</span> <span class="number">0.0f</span>; VkClearColorValue clearColor <span class="operator">=</span> {{ <span class="number">0.0f</span><span class="operator">,</span> m_green<span class="operator">,</span> <span class="number">0.0f</span><span class="operator">,</span> <span class="number">1.0f</span> }}; VkClearDepthStencilValue clearDS <span class="operator">=</span> { <span class="number">1.0f</span><span class="operator">,</span> <span class="number">0</span> }; VkClearValue clearValues<span class="operator">[</span><span class="number">2</span><span class="operator">]</span>; memset(clearValues<span class="operator">,</span> <span class="number">0</span><span class="operator">,</span> <span class="keyword">sizeof</span>(clearValues)); clearValues<span class="operator">[</span><span class="number">0</span><span class="operator">]</span><span class="operator">.</span>color <span class="operator">=</span> clearColor; clearValues<span class="operator">[</span><span class="number">1</span><span class="operator">]</span><span class="operator">.</span>depthStencil <span class="operator">=</span> clearDS; VkRenderPassBeginInfo rpBeginInfo; memset(<span class="operator">&</span>rpBeginInfo<span class="operator">,</span> <span class="number">0</span><span class="operator">,</span> <span class="keyword">sizeof</span>(rpBeginInfo)); rpBeginInfo<span class="operator">.</span>sType <span class="operator">=</span> VK_STRUCTURE_TYPE_RENDER_PASS_BEGIN_INFO; rpBeginInfo<span class="operator">.</span>renderPass <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">></span>defaultRenderPass(); rpBeginInfo<span class="operator">.</span>framebuffer <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">></span>currentFramebuffer(); <span class="keyword">const</span> <span class="type"><a href="../qtcore/qsize.html">QSize</a></span> sz <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">></span>swapChainImageSize(); rpBeginInfo<span class="operator">.</span>renderArea<span class="operator">.</span>extent<span class="operator">.</span>width <span class="operator">=</span> sz<span class="operator">.</span>width(); rpBeginInfo<span class="operator">.</span>renderArea<span class="operator">.</span>extent<span class="operator">.</span>height <span class="operator">=</span> sz<span class="operator">.</span>height(); rpBeginInfo<span class="operator">.</span>clearValueCount <span class="operator">=</span> <span class="number">2</span>; rpBeginInfo<span class="operator">.</span>pClearValues <span class="operator">=</span> clearValues; VkCommandBuffer cmdBuf <span class="operator">=</span> m_window<span class="operator">-</span><span class="operator">></span>currentCommandBuffer(); m_devFuncs<span class="operator">-</span><span class="operator">></span>vkCmdBeginRenderPass(cmdBuf<span class="operator">,</span> <span class="operator">&</span>rpBeginInfo<span class="operator">,</span> VK_SUBPASS_CONTENTS_INLINE); <span class="comment">// Do nothing else. We will just clear to green, changing the component on</span> <span class="comment">// every invocation. This also helps verifying the rate to which the thread</span> <span class="comment">// is throttled to. (The elapsed time between startNextFrame calls should</span> <span class="comment">// typically be around 16 ms. Note that rendering is 2 frames ahead of what</span> <span class="comment">// is displayed.)</span> m_devFuncs<span class="operator">-</span><span class="operator">></span>vkCmdEndRenderPass(cmdBuf); m_window<span class="operator">-</span><span class="operator">></span>frameReady(); m_window<span class="operator">-</span><span class="operator">></span>requestUpdate(); <span class="comment">// render continuously, throttled by the presentation rate</span> } </pre> <p>To get continuous updates, the example simply invokes <a href="qwindow.html#requestUpdate">QWindow::requestUpdate</a>() in order to schedule a repaint.</p> <a name="running-the-example"></a> <h2 id="running-the-example">Running the Example</h2> <p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p> <p>Files:</p> <ul> <li><a href="qtgui-hellovulkanwindow-hellovulkanwindow-cpp.html">hellovulkanwindow/hellovulkanwindow.cpp</a></li> <li><a href="qtgui-hellovulkanwindow-hellovulkanwindow-h.html">hellovulkanwindow/hellovulkanwindow.h</a></li> <li><a href="qtgui-hellovulkanwindow-hellovulkanwindow-pro.html">hellovulkanwindow/hellovulkanwindow.pro</a></li> <li><a href="qtgui-hellovulkanwindow-main-cpp.html">hellovulkanwindow/main.cpp</a></li> </ul> </div> <!-- @@@hellovulkanwindow --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>