simplified method to draw camera frustum in oF

drawfrustum.cpp

void ofCamera::drawFrustum(const ofRectangle & viewport) const {
	ofPushMatrix();

	// In World Space, the camera frustum is the "capped pyramid" which 
	// contains everything which can be seen from a camera. 
	//
	// In Clip Space, the frustum is defined as a box with dimensions: -1, -1, -1 to +1, +1, +1.
	//
	// Much simpler. 
	//
	// We therefore want to draw our frustum as if in Clip Space. 
	// For this, we must find a matrix which will transform Clip Space 
	// back to World Space. 
	

	// Note: globalTransformMatrix == inverse(modelViewMatrix)
	glm::mat4 clipSpaceToWorld = getGlobalTransformMatrix() * glm::inverse(getProjectionMatrix(viewport));

	// Move into Clip Space - this matrix will transform anything we 
	// draw from Clip Space to World Space
	ofMultMatrix(clipSpaceToWorld);

	// Anything we draw now is transformed from Clip Space back to World Space

	ofPushStyle();
	ofNoFill();
	ofDrawBox(0, 0, 0, 2.f, 2.f, 2.f); // In Clip Space, the frustum is standardised to be a box of dimensions -1,1 in each axis
	ofPopStyle();

	ofPopMatrix();
}