QParameter Class

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