The CMS RPC(Resistive Plate Chambers) is a special purpose detector providing fast information for the level-1 trigger. Its geometry follows the muon detector geometry. This consists in four stations interleaved with the iron return plates. These stations form four concentric cylinders around the beam line in the barrel region, and four disks perpendicular to the beam line in the endcaps. In the barrel we have a further subdivision in five wheels.Each wheel has 12 wedges.

Graphical objects can be used to represent RPC information like:

• detector geometry
• event data generated by RPC
• information in the construction database
• information from DCS(Detector Control System)
• other ...

• Check reconstruction algorithms correctness
• Follow the construction of the detector
• Monitor prototypes performance

What we have now
CMS has chosen to build a toolkit of visualization objects called Iguana, instead of a stand-alone monolithic program. This toolkit is already used to allow visualization in Orca and Oscar.In Orca RPC chambers are described as a OpenInventor scene with a graph of around 2000 boxes each one corresponding approximately to a single chamber.
In Oscar, Iguana is used to visualize the description of the detector in terms of Geant 4 volumes and materials.
The simulated signal in the detector is represented by a single set of points in space.
Simulated and reconstructed tracks are also represented in space(Fig).
Track segments in the muon stations are represented as arrows in space.
In Iguana there are also the usual objects used for statistical analysis (histograms,scatter plots,...)

Our goal
All this works inside Orca but has some problems,the principal one being that Orca requires a lot of computer resources, making its use for visualization difficult. So our main goal is to make these graphics objects work also outside ORCA in a stand-alone program and in a web interface. This stand-alone program will be built using Iguana,instead for the Web interface we will use other tools. They should improve the existing visualization performance by:

• Allowing easier selection of the part of the detector to be displayed in 3D
• Allowing the definition of greater detail for the detector geometry.
• Building "maps" of the whole RPC

Objects to be developed

• 2D map of the whole RPC detector :prototype: here you can see all RPC chambers in a single picture. This is composed by 2D maps of endcap disks and barrel layers. The map of barrel layer is represented by "cutting" it at phi=0 and placing the chambers in twelve rows:one for each wedge.
• 2D schematic representation of the RPC detector and trigger to select parts of the detector like trigger towers, trigger sections, etc...

Why a stand alone program
We suggest in some cases the use of a stand-alone program because using ORCA has the following problems:

• Running the visualization program inside Orca means adding to the big overhead of managing 3D scene graphs, the normal Orca overhead (500Mb of central memory) .
• The time to process each event can be very long.

The solution is to make a stand-alone program which reads events created by ORCA and ready to be visualized . This program reads the detector description in XML using DDD.
To share events between CMS programs an XML format should be setup (like what we have already for the detector). In this way, you don't need to use COBRA, Objectivity and similar stuff(expensive in terms of computer resources) when you want only to do some simple visualization.(*)
The program used to create the RPC map is a first approximation of this stand-alone program. It has the geometry data directly in the code: I am planning to start using it to test an XML description of the detector using the DDD toolkit.

Why a Web interface
Instead a web interface can be very useful when there is little interactivity, for example to display information in the rpc construction data base: prototype. In general we should develop always a Web interface for these tasks , unless its implementation produces something which is too limited to be useful.