CameraClipping.cpp

void render()
{
	// update camera based on mouse position, WASD, etc.

	// calculate the view frustum
	viewFrustum.calculate( 60.0f , (float)window->getWidth()/(float)window->getHeight() , 0.1f , 100.0f );

	// convert the view frustum to world space
	viewFrustum.convertToWorldSpace( camera->getInverseViewMatrix() );

	const vec3& bottomLeft = viewFrustum.getNearBottomLeft();
	const vec3& bottomRight = viewFrustum.getNearBottomRight();

	// near clipping plane, left bottom vertex
	float elevation = /* get the elevation of your terrain at the bottom left view frustum position, e.g. getTerrainHeight( bottomLeft.x , bottomLeft.z ); */;
	if ( bottomLeft.y <= elevation )
	{
		// move the camera up 
		camera->setPosition( vec3( camera->getPosition().x , elevation + A_LITTLE_BIT_EXTRA , camera->getPosition().z ) );
	}

	// near clipping plane, right bottom vertex
	float elevation = /* get the elevation of your terrain at the bottom right view frustum position, e.g. getTerrainHeight( bottomRight.x , bottomRight.z ); */;
	if ( bottomRight.y <= elevation ) 
	{
		// move the camera up
		camera->setPosition( vec3( camera->getPosition().x , elevation + A_LITTLE_BIT_EXTRA , camera->getPosition().z ) );
	}

	// do the rest of the rendering
}