Use rtt with fitting size.

src/graphics/irr_driver.cpp

@@ -1562,7 +1562,9 @@ void IrrDriver::onLoadWorld()
 {
     if (m_glsl)
     {
-        m_rtts = new RTT();
+        const core::recti &viewport = Camera::getCamera(0)->getViewport();
+        size_t width = viewport.LowerRightCorner.X - viewport.UpperLeftCorner.X, height = viewport.LowerRightCorner.Y - viewport.UpperLeftCorner.Y;
+        m_rtts = new RTT(width, height);
     }
 }
 // ----------------------------------------------------------------------------

src/graphics/rtts.cpp

@@ -51,14 +51,14 @@ static GLuint generateFBO(GLuint ColorAttachement, GLuint DepthAttachement)
     return fbo;
 }
 
-RTT::RTT()
+RTT::RTT(size_t width, size_t height)
 {
     initGL();
     using namespace video;
     using namespace core;
 
     IVideoDriver * const drv = irr_driver->getVideoDriver();
-    const dimension2du res(UserConfigParams::m_width, UserConfigParams::m_height);
+    const dimension2du res(width, height);
     const dimension2du half = res/2;
     const dimension2du quarter = res/4;
     const dimension2du eighth = res/8;

src/graphics/rtts.hpp

@@ -113,7 +113,7 @@ enum TypeFBO
 class RTT
 {
 public:
-    RTT();
+    RTT(size_t width, size_t height);
     ~RTT();
 
     unsigned getShadowFBO() const { return shadowFBO; }