qgsgradientbackgroundentity.cpp

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/***************************************************************************
  qgsgradientbackgroundentity.cpp
  --------------------------------------
  Date                 : April 2026
  Copyright            : (C) 2026 by Dominik Cindrić
  Email                : viper dot miniq at gmail dot com
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgsgradientbackgroundentity.h"
 
#include "qgs3dutils.h"
 
#include <QString>
#include <QUrl>
#include <QVector>
#include <QVector3D>
#include <Qt3DCore/QAttribute>
#include <Qt3DCore/QBuffer>
#include <Qt3DCore/QGeometry>
#include <Qt3DRender/QDepthTest>
#include <Qt3DRender/QEffect>
#include <Qt3DRender/QFilterKey>
#include <Qt3DRender/QGeometryRenderer>
#include <Qt3DRender/QGraphicsApiFilter>
#include <Qt3DRender/QMaterial>
#include <Qt3DRender/QNoDepthMask>
#include <Qt3DRender/QParameter>
#include <Qt3DRender/QRenderPass>
#include <Qt3DRender/QShaderProgram>
#include <Qt3DRender/QTechnique>
 
#include "moc_qgsgradientbackgroundentity.cpp"
 
using namespace Qt::StringLiterals;
 
QgsGradientBackgroundEntity::QgsGradientBackgroundEntity( const QColor &topColor, const QColor &bottomColor, Qt3DCore::QNode *parent )
  : Qt3DCore::QEntity( parent )
  , mEffect( new Qt3DRender::QEffect( this ) )
  , mMaterial( new Qt3DRender::QMaterial( this ) )
  , mGl3Technique( new Qt3DRender::QTechnique( this ) )
  , mFilterKey( new Qt3DRender::QFilterKey( this ) )
  , mGl3RenderPass( new Qt3DRender::QRenderPass( this ) )
  , mMesh( new Qt3DRender::QGeometryRenderer( this ) )
  , mGlShader( new Qt3DRender::QShaderProgram( this ) )
  , mTopColorParameter( new Qt3DRender::QParameter( u"topColor"_s, QVariant() ) )
  , mBottomColorParameter( new Qt3DRender::QParameter( u"bottomColor"_s, QVariant() ) )
{
  const QColor linearTopColor = Qgs3DUtils::srgbToLinear( topColor );
  const QColor linearBottomColor = Qgs3DUtils::srgbToLinear( bottomColor );
  mTopColorParameter->setValue( QVector3D( linearTopColor.redF(), linearTopColor.greenF(), linearTopColor.blueF() ) );
  mBottomColorParameter->setValue( QVector3D( linearBottomColor.redF(), linearBottomColor.greenF(), linearBottomColor.blueF() ) );
 
  mGl3Technique->graphicsApiFilter()->setApi( Qt3DRender::QGraphicsApiFilter::OpenGL );
  mGl3Technique->graphicsApiFilter()->setMajorVersion( 3 );
  mGl3Technique->graphicsApiFilter()->setMinorVersion( 3 );
  mGl3Technique->graphicsApiFilter()->setProfile( Qt3DRender::QGraphicsApiFilter::CoreProfile );
 
  mFilterKey->setParent( mEffect );
  mFilterKey->setName( u"renderingStyle"_s );
  mFilterKey->setValue( u"forward"_s );
 
  mGl3Technique->addFilterKey( mFilterKey );
 
  Qt3DRender::QDepthTest *depthTest = new Qt3DRender::QDepthTest();
  depthTest->setDepthFunction( Qt3DRender::QDepthTest::LessOrEqual );
  Qt3DRender::QNoDepthMask *noDepthMask = new Qt3DRender::QNoDepthMask();
 
  mGl3RenderPass->addRenderState( depthTest );
  mGl3RenderPass->addRenderState( noDepthMask );
 
  mGlShader->setVertexShaderCode( Qt3DRender::QShaderProgram::loadSource( QUrl( u"qrc:/shaders/gradient_static.vert"_s ) ) );
  mGlShader->setFragmentShaderCode( Qt3DRender::QShaderProgram::loadSource( QUrl( u"qrc:/shaders/gradient_background.frag"_s ) ) );
  mGl3RenderPass->setShaderProgram( mGlShader );
 
  mGl3Technique->addRenderPass( mGl3RenderPass );
  mEffect->addTechnique( mGl3Technique );
 
  mMaterial->setEffect( mEffect );
  mMaterial->addParameter( mTopColorParameter );
  mMaterial->addParameter( mBottomColorParameter );
 
  Qt3DCore::QGeometry *geom = new Qt3DCore::QGeometry( this );
  Qt3DCore::QAttribute *posAttr = new Qt3DCore::QAttribute( this );
  // clang-format off
  const QVector<float> verts = { -1.0f, -1.0f, 0.0f,
                                  1.0f, -1.0f, 0.0f,
                                 -1.0f,  1.0f, 0.0f,
                                 -1.0f,  1.0f, 0.0f,
                                  1.0f, -1.0f, 0.0f,
                                  1.0f,  1.0f, 0.0f };
  // clang-format on
  Qt3DCore::QBuffer *vbo = new Qt3DCore::QBuffer( this );
  vbo->setData( QByteArray( reinterpret_cast<const char *>( verts.constData() ), verts.size() * sizeof( float ) ) );
  posAttr->setName( Qt3DCore::QAttribute::defaultPositionAttributeName() );
  posAttr->setVertexBaseType( Qt3DCore::QAttribute::Float );
  posAttr->setVertexSize( 3 );
  posAttr->setAttributeType( Qt3DCore::QAttribute::VertexAttribute );
  posAttr->setBuffer( vbo );
  posAttr->setByteStride( 3 * sizeof( float ) );
  posAttr->setCount( 6 );
  geom->addAttribute( posAttr );
  mMesh->setPrimitiveType( Qt3DRender::QGeometryRenderer::Triangles );
  mMesh->setGeometry( geom );
 
  addComponent( mMesh );
  addComponent( mMaterial );
}