e2ad97eef9
Fixes: QTBUG-117884 Pick-to: 6.6 Change-Id: I33c7b1cbfaeae866dffb0e89a5d09d775736d886 Reviewed-by: Topi Reiniö <topi.reinio@qt.io> (cherry picked from commit 98ee4d9e37a1038d46f0c0494332c0ed46dbb323) Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
150 lines
4.8 KiB
Plaintext
150 lines
4.8 KiB
Plaintext
// Copyright (C) 2018 The Qt Company Ltd.
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// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
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/*!
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\example hellogles3
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\title Hello GLES3 Example
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\ingroup examples-widgets-opengl
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\examplecategory {Graphics}
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\examplecategory {Mobile}
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\brief Demonstrates OpenGL ES 3.0 functions via QOpenGLExtraFunctions.
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\image hellogles3-example.png
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\section1 Overview
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This example demonstrates easy, cross-platform usage of OpenGL ES 3.0
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functions via QOpenGLExtraFunctions in an application that
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works identically on desktop platforms with OpenGL 3.3 and mobile/embedded
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devices with OpenGL ES 3.0.
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This example has no QWidget dependencies, it uses QOpenGLWindow, a
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convenience subclass of QWindow that allows easy implementation of windows
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that contain OpenGL-rendered content. In this sense it complements the
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\l{OpenGL Window Example}, which shows the implementation of an OpenGL-based
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QWindow without using the convenience subclass.
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The Qt logo shape implementation is included from the \l{Hello GL2 Example}.
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In other aspects pertaining to using OpenGL there are the following
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differences.
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\list
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\li The OpenGL context creation has to have a sufficiently high version
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number for the features that are in use.
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\li The shader's version directive is different.
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\endlist
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\section1 Setting up in main.cpp
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Here we instantiate our QGuiApplication, QSurfaceformat and set its
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\l{QSurfaceFormat::depthBufferSize()}{depth buffer size}:
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\quotefromfile hellogles3/main.cpp
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\skipto int main(int argc, char *argv[])
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\printuntil fmt.setDepthBufferSize(24);
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We request an OpenGL 3.3 core or OpenGL ES 3.0 context, depending on
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QOpenGLContext::openGLModuleType():
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\skipto if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
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\printuntil QSurfaceFormat::setDefaultFormat(fmt);
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We set the default surface format and instantiate our GLWindow \c glWindow.
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\section1 Implementing GLWindow
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This class delivers the features of the example application.
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To start, \c GLWindow is declared by implementing a subclass of
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QOpenGLWindow:
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\quotefromfile hellogles3/glwindow.h
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\skipto class GLWindow : public QOpenGLWindow
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\printto {
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The following properties are declared using Q_PROPERTY:
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\printto public:
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The following public functions are declared:
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\printto private slots:
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The following private objects are declared:
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\printto };
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On the implementation side, those functions that are not declared inline are
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implemented (or re-implemented) in \c{glwindow.cpp}. The following selections
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will cover implementation particulars pertaining to the use of OpenGL ES 3.0.
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\section2 Animations
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The following code pertains to the animations, and won't be explored here:
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\quotefromfile hellogles3/glwindow.cpp
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\skipto GLWindow::GLWindow()
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\printto static const char *vertexShaderSource =
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For more information see the documentation for \l QPropertyAnimation,
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\l QSequentialAnimationGroup.
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\section2 Shaders
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The shaders are defined like so:
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\printto QByteArray versionedShaderCode(const char *src)
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\note These are OpenGL version agnostic. We take this and append
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the version like so:
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\printto void GLWindow::initializeGL()
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\section2 Initializing OpenGL
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Initializing the shader program in handled by \c initializeGL():
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\printuntil m_program = new QOpenGLShaderProgram;
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\skipto m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, versionedShaderCode(vertexShaderSource));
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Now the OpenGL version is prepended and the various matrices and light
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position is set:
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\printuntil m_lightPosLoc = m_program->uniformLocation("lightPos");
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While not strictly required for ES 3, a vertex array object is created.
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\skipto delete m_vao;
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\printuntil f->glEnable(GL_CULL_FACE);
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\section2 Resizing the window
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The perspective needs to be aligned with the new window size as so:
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\skipto void GLWindow::resizeGL(int w, int h)
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\printto void GLWindow::paintGL()
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\section2 Painting
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We use QOpenGLExtraFunctions instead of QOpenGLFunctions as we want to
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do more than what GL(ES) 2.0 offers:
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\printuntil QOpenGLExtraFunctions *f = QOpenGLContext::currentContext()->extraFunctions();
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We clear the screen and buffers and bind our shader program and texture:
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\printuntil m_texture->bind();
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Logic for handling an initial \c paintGL() call or a call after a
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\c resizeGL() call is implemented like so:
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\printuntil }
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Last, we demonstrate a function introduced in OpenGL 3.1 or OpenGL ES 3.0:
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\skipto f->glDrawArraysInstanced(GL_TRIANGLES, 0, m_logo.vertexCount(), 32 * 36);
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\printuntil }
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This works because we earlier requested 3.3 or 3.0 context.
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*/
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