Rendering to texture (RTT) in CEGUI

Written for CEGUI 0.8

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Works with versions 0.8.x (stable)

Works with latest CEGUI stable!

Since version 0.8 the new GUIContext class allows it to render your CEGUI interface into a texture instead of rendering it normally into your main buffer.

CEGUI::System& ceSystem = CEGUI::System::getSingleton();
//Taking some random values as example for a GUIContext size.
int width = 1024;
int height = 800;
CEGUI::Sizef size(static_cast<float>(width), static_cast<float>(height));
 
// We create a CEGUI texture target and create a GUIContext that will use it.
CEGUI::TextureTarget* renderTextureTarget = ceSystem.getRenderer()->createTextureTarget();
CEGUI::GUIContext* renderGuiContext = ceSystem.createGUIContext(static_cast<CEGUI::RenderTarget&>(*renderTextureTarget) );
renderTextureTarget->declareRenderSize(size);
 
// We create a BasicImage and set the Texture
textureTargetImage = static_cast<CEGUI::BitmapImage*>(&CEGUI::ImageManager::getSingleton().create("BitmapImage", "SomeGroup/MyTexturesName"));
textureTargetImage->setTexture(&renderTextureTarget->getTexture());
 
// We size the image using a function
setTextureTargetImageArea(static_cast<float>(height), static_cast<float>(width));

Here is the function for sizing the BasicImage:

void setTextureTargetImageArea(float height, float width)
{
    if(d_textureTarget)
    {
        bool isTextureTargetVerticallyFlipped = renderTextureTarget->isRenderingInverted();
        CEGUI::Rectf renderArea;
        if (isTextureTargetVerticallyFlipped)
            renderArea = CEGUI::Rectf(0.0f, height, width, 0.0f);
        else
            renderArea = CEGUI::Rectf(0.0f, 0.0f, width, height);
 
 
        if(textureTargetImage)
            textureTargetImage->setImageArea(renderArea);
    }
}

If you want to retrieve the renderer-specific texture from a CEGUI texture you will need to cast it:

For example for OpenGL:

CEGUI::OpenGLTexture& glTexture = static_cast<CEGUI::OpenGLTexture&>(d_textureTarget->getTexture());

After that you can use the member function to receive whatever render-specific traits you need, such as the textureID in Opengl as an unsigned integer, etc.