[SOLVED] Q RTT: How to set transparent color?

[Van]

We are using the code supplied in the examples on rendering to texture (RTT). However, how do you set the transparency color? We would like to set it to "black".

If I remember correctly, the material script command is something like scene_blend colour_blend in the pass section. But how would one do it in code?

[klauss]

Why don't you use a true transparent colour (Ogre::ColourValue(0,0,0,0)) as clear colour, and then render using alpha to it, and finally use alpha blend when rendering from the RTT?

[xavier]

If I remember correctly, the material script command is something like scene_blend colour_blend in the pass section. But how would one do it in code?

pass->setSceneBlending()

Code: Select all

        void setSceneBlending( const SceneBlendType sbt );

    enum SceneBlendType
    {
        /// Make the object transparent based on the final alpha values in the texture
        SBT_TRANSPARENT_ALPHA,
        /// Make the object transparent based on the colour values in the texture (brighter = more opaque)
        SBT_TRANSPARENT_COLOUR,
        /// Add the texture values to the existing scene content
        SBT_ADD,
		/// Multiply the 2 colours together
		SBT_MODULATE,
        /// The default blend mode where source replaces destination
        SBT_REPLACE
        // TODO : more
    };

Available on Pass and Technique (the Technique method will apply to all contained passes).

[Kencho]

Here go the links to the methods Xavier exposed:
Pass::setSceneBlending ()
Technique::setSceneBlending ()

[Van]

For those people in the future who find this:

Code: Select all

	// Load the Ogre Entity
	Ogre::Entity *mEntity = mSceneManager->createEntity( "Hud/SPS/VectorArrow", "vectorarrow.mesh" );

	// Create the Ogre SceneNode for the Entity
	mVectorArrowNode = mSceneManager->getRootSceneNode()->createChildSceneNode("HudSPSVectorArrowNode");
	mVectorArrowNode->attachObject( mEntity );
	mVectorArrowNode->setPosition( Ogre::Vector3::ZERO );
	mVectorArrowNode->setDirection( Ogre::Vector3::NEGATIVE_UNIT_Z );
	//mVectorArrowNode->setScale( 1.0f, 1.0f, 1.0f );
	mVectorArrowNode->setScale( 0.75f, 0.75f, 0.75f );
	mVectorArrowNode->setVisible( true );
	mVectorArrowNode->setFixedYawAxis( false );

	// Create an Ogre Render To Texture process.
	Ogre::RenderTexture *mRTT = mGlobalResource->OgreRoot->getRenderSystem()->createRenderTexture(
		"Hud/SPS/VectorArrow/RTT",
		128, 128,
		Ogre::TEX_TYPE_2D,
		Ogre::PF_B8G8R8A8 );	// <<< Note we use an ALPHA channel for transparency.

	// Create a camera to render from.
	Ogre::Camera *mRTTCam = mSceneManager->createCamera( "Hud/SPS/VectorArrow/Camera" );

	// Create a scene node to hold the camera.
	mVectorArrowCameraNode = mSceneManager->getRootSceneNode()->createChildSceneNode( "Hud/SPS/VectorArrow/CameraNode" );
	mVectorArrowCameraNode->attachObject( mRTTCam );
	mRTTCam->setPosition( Ogre::Vector3::ZERO );
	mRTTCam->setNearClipDistance( 0.5f );
	mRTTCam->setFarClipDistance( 100.0f );
	mRTTCam->setDirection( Ogre::Vector3::NEGATIVE_UNIT_Z );
	
	// Position the camera node just behind the subject node. Becarefull of the NearClip distance.
	mVectorArrowCameraNode->setPosition( 0.0f, 0.0f, 1.5f );
	mVectorArrowCameraNode->lookAt( Ogre::Vector3::ZERO, Ogre::Node::TS_WORLD, Ogre::Vector3::NEGATIVE_UNIT_Z );

	// Create a Ogre Viewport for the camera.
	Ogre::Viewport *mVP = mRTT->addViewport( mRTTCam );
	mVP->setOverlaysEnabled( false );
	mVP->setClearEveryFrame( true );
	mVP->setBackgroundColour( Ogre::ColourValue(0,0,0,0) );

	// Set the material as transparent ( Make sure RTT is set to Ogre::PF_B8G8R8A8 )
	Ogre:: MaterialPtr mMat = Ogre::MaterialManager::getSingleton().create(
		"Hud/SPS/VectorArrow/Resource", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME ); 
	mMat->setSceneBlending( Ogre::SceneBlendType::SBT_TRANSPARENT_COLOUR );

	// Create CEGUI texture from the Ogre RTT
	CEGUI::Texture *mTexture = mGlobalResource->CEGUIRenderer->createTexture( (CEGUI::utf8*)"Hud/SPS/VectorArrow/RTT" );

	// Create CEGUI Imageset
	CEGUI::Imageset *mRTTImageSet = CEGUI::ImagesetManager::getSingleton().createImageset( (CEGUI::utf8*)"Hud/SPS/VectorArrow/ImageSet", mTexture );
	
	// Define a CEGUI Image
	mRTTImageSet->defineImage( 
		(CEGUI::utf8*)"Hud/SPS/VectorArrow/Image", 
		CEGUI::Point( 0.0f, 0.0f ),
		CEGUI::Size( mTexture->getWidth(), mTexture->getHeight() ),
		CEGUI::Point( 0.0f, 0.0f ) );

	// Set the Image in the StaticImage widow.
	mSIVectorArrow->setImage( &mRTTImageSet->getImage( (CEGUI::utf8*)"Hud/SPS/VectorArrow/Image") );

[OvermindDL1]

It will still get lost in the forums. You should wiki it.

[hawkeye]

well, i found it, this looks a damn much like what im looking for, thnx