QParameter Class | Qt 3D 5.12.8

Qt 5.12 | Qt 3D | C++ Classes | QParameter

Qt 5.12.8 Reference Documentation

# 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

- List of all members, including inherited members
- Obsolete members

## Properties

- name : QString
- value : QVariant

- 3 properties inherited from Qt3DCore::QNode
- 1 property inherited from QObject

## Public Functions

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

- 13 public functions inherited from Qt3DCore::QNode
- 31 public functions inherited from QObject

## Public Slots

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

- 3 public slots inherited from Qt3DCore::QNode
- 1 public slot inherited from QObject

## Signals

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

- 4 signals inherited from Qt3DCore::QNode
- 2 signals inherited from QObject

## Static Public Members

const QMetaObject | staticMetaObject

- 9 static public members inherited from QObject

### Additional Inherited Members

- 2 protected functions inherited from Qt3DCore::QNode
- 9 protected functions inherited from QObject

## Detailed Description

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

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(Qt3DCore::QNode *parent = nullptr)

Constructs a new QParameter with the specified parent.

### 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(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.