QParameter Class

(Qt3DRender::QParameter)

Provides storage for a name and value pair. This maps to a shader uniform. More...

Header: #include <Qt3DRender/QParameter>
qmake: QT += 3drender
Instantiated By: Parameter
Inherits: Qt3DCore::QNode

Properties

Public Functions

QParameter(const QString &name, Qt3DRender::QAbstractTexture *texture, Qt3DCore::QNode *parent = nullptr)
QParameter(const QString &name, const QVariant &value, Qt3DCore::QNode *parent = nullptr)
QParameter(Qt3DCore::QNode *parent = nullptr)
QString name() const
QVariant value() const

Public Slots

void setName(const QString &name)
void setValue(const QVariant &dv)

Signals

void nameChanged(const QString &name)
void valueChanged(const QVariant &value)

Detailed Description

A QParameter can be referenced by a QRenderPass, QTechnique, QEffect, QMaterial, QTechniqueFilter, QRenderPassFilter. At runtime, depending on which shader is selected for a given step of the rendering, the value contained in a QParameter will be converted and uploaded if the shader contains a uniform with a name matching that of the QParameter.

QParameter *param = new QParameter();
param->setName(QStringLiteral("diffuseColor"));
param->setValue(QColor::fromRgbF(0.0f, 0.0f, 1.0f, 1.0f));

// Alternatively you can create and set a QParameter this way
QParameter *param2 = new QParameter(QStringLiteral("diffuseColor"), QColor::fromRgbF(0.0f, 0.0f, 1.0f, 1.0f));

// Such QParameters will work with the following GLSL uniform shader declarations
// uniform vec4 diffuseColor;
// uniform vec3 diffuseColor;
// uniform vec2 diffuseColor;
// uniform float diffuseColor;

Note: some care must be taken to ensure the value wrapped by a QParameter can actually be converted to what the real uniform expect. Giving a value stored as an int where the actual shader uniform is of type float could result in undefined behaviors.

Note: when the targeted uniform is an array, the name should be the name of the uniform with [0] appended to it.

QParameter *param = new QParameter();
QVariantList values = QVariantList() << 0.0f << 1.0f << 2.0f << 3.0f << 4.0f << 883.0f << 1340.0f << 1584.0f;

param->setName(QStringLiteral("diffuseValues[0]"));
param->setValue(values);

// Matching GLSL shader uniform  declaration
// uniform float diffuseValues[8];

When it comes to texture support, the QParameter value should be set to the appropriate QAbstractTexture subclass that matches the sampler type of the shader uniform.

QTexture2D *texture = new QTexture2D();
...
QParameter *param = new QParameter();
param->setName(QStringLiteral("diffuseTexture"));
param->setValue(QVariant::fromValue(texture));

// Works with the following GLSL uniform shader declaration
// uniform sampler2D diffuseTexture

See also QAbstractTexture.

Property Documentation

name : QString

Specifies the name of the parameter

Access functions:

QString name() const
void setName(const QString &name)

Notifier signal:

void nameChanged(const QString &name)

value : QVariant

Specifies the value of the parameter

Access functions:

QVariant value() const
void setValue(const QVariant &dv)

Notifier signal:

void valueChanged(const QVariant &value)

Member Function Documentation

QParameter::QParameter(const QString &name, Qt3DRender::QAbstractTexture *texture, Qt3DCore::QNode *parent = nullptr)

Constructs a new QParameter with the specified parent name and takes its value from texture.

QParameter::QParameter(const QString &name, const QVariant &value, Qt3DCore::QNode *parent = nullptr)

Constructs a new QParameter with the specified parent name and value.

QParameter::QParameter(Qt3DCore::QNode *parent = nullptr)

Constructs a new QParameter with the specified parent.

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