For this project you will be assigned in to groups of 4/5 people, the members of each group being selected by the unit coordinator.

The Team members a given here.

With four people in each group (one team has 3 people), it is expected that a high level of achievement will result. However it is imperative that any difficulties in working as a team are immediately resolved to the satisfaction of the unit coordinator. Failure to act quickly on establishing a functioning team could jeopardise the final implementation.

The task of each team for the project is to implement the Marching Cubes algorithm for user definable iso-surfaces given a volume data-set. There will be two main parts to the project.

The Project

Part I - Basic

An implementation of the Marching Cubes algorithm. Given a data set consisting of a series of "8 bit grey" images in the PGM format, where the user defines the image dimensions and number of slices, your application should generate a VRML output of the user stipulated iso-surface value.

The Marking Scheme will be based on the

• A submitted report including user documentation, a description of your system, implementation details and and installation guide.
• The quality of the submitted code
• The successful installation of your system, and your test cases
• successful completion of my run-time tests

The "flawless" implementation and testing of the application from Part I will result in a solid pass for the project.

Part II - Bells and some Whistles

Having completed Part I you may wish to tackle the following

• incorporation of surface normals - your program should output the surface normal of each generated triangular facet, using any of the methods described in the lecture notes.
• decimation - a technique to reduce the number of triangle primitives.

The "flawless" implementation and testing of the application from Part II would result in full marks for the project.

Part III - Above and Beyond

For those wishing to test their abilities there will be additional marks for attempting to complete some or all of the following

• Enabling multiple iso-surfaces to be stipulated and rendered.
• Incorporating transparency on some iso-surfaces.
• Including the capacity for iso-surface colouring.
• Enable "sectional cut aways" to be displayed. Here an iso-surface is not rendered entirely b but the user can stipulate a section of the data that is not to be rendered.

The "flawless" implementation and testing of the application from Part III would result in an additional 10 marks for the project.

Details of the algorithm that is to be implemented have been described in lectures and can be found in the textbook by Watt and Watt (Chapter 13) and elsewhere.

The result of your program will be visualised via a VRML browser, of which there are two available in Linux, octagaplayer and vrmlview. Both render VRML2.0 model specifications and vrmlview also handles VRML1.0. Your application must generate output in one or either of these formats.

Of course, by using ANSI C, C++, or Java (or whatever language you choose) and VRML, you can develop your solution anywhere that suitable tools are available. If the output of your program is in the correct format, it can be rendered by these programs and they will deal with shading, rotation, etc. Your program will restrict itself solely to the extraction of the required surface(s).

Below is a schedule that will help you plan your activities:

Week	Date	Activities
5	20/08	Project commencement. Informal specification
6	30/08	Formal Project Specification. Project teams established.
6-13		Team development of the application.
	10/09 - 14/09	Mid-semester non-teaching week.
9	27/09/	Students should have a working version of the system for Part I.
13	Wednesday 24/10 at 4pm	Project report and source code due.

Data-sets

Three data-sets are given in the /cslinux/examples/CITS4241/Project directory.

1. The first data-set can be found in the sub-directory FullHead-8bits. This data-set, which has been used in the Lab 1 and Lab 2 exercises, has been modified and simplified for this project.  The data-set contains 94 slices of 256 × 256 pixel values.  Each slice is stored in a file named HEADSQ.nnn where nnn is a number in the range [001, 094].  Pixels of  each slice are of type unsigned char (1 byte), varying from 0 (black) to 255 (white).  More details about the data-set are given in the README file there.

   The only additional piece of input information that you need is the real distance between data points, i.e., the voxel aspect ratio. This is
   

   x : y : z = 0.8 : 0.8 : 1.5
   You can read these as mm, so the original full head images are taken as a volume of 20.5 × 20.5 × 14.1 cm³.

2. The second data-set can be found in the sub-directory Crachami-8bits. This data-set contains 275 slices of 512 × 512 pixel values. Each slice is stored in a file named SKULL.nnn where nnn is a number in the range [001, 275]. Similar to the first data-set, pixels of each slice are of type unsigned char.  More details about the data-set are given in the README and the cc-8bit_info.txt file there.

3. The third data-set is the simplest data-set that your program should be tested on first. It contains 33 slices of 33 × 33 pixels. The data-set is generated by a simple mathematical function --- the hyperboloid. The iso-contour value used in the surface generation is 383.519 (on the original values). The file format is identical to those of the head and skull data, except that pixels in each slice are of type unsigned short (2 bytes).  Each slice is stored in a file named hyper.nnn where nnn is a number in the range [000, 032].   This data-set can be found in the sub-directory Hyperboloid.
Some results VRML1.0 are also provided for the third data-set for you to test-check your program:
• 8336 triangles from the above test check. The VRML1.0 file is hyper-VRML1.wrl. This file has the normal vectors included with the triangles.
• 8336 triangles from the above test check.  The VRML1.0 file is hyper-VRML1-nonormals.wrl.  This file does not have the normal vectors calculated.  The subtle difference in shading is noticeable.
• 2009 triangles from the above test check, after 75% decimation.  The VRML1.0 file is hyper-deci-VRML1.wrl.  This file has the normal vectors included with the triangles.  Note that it is difficult to distinguish between this file and the first one.
• 2009 triangles from the above test check, after 75% decimation.  The VRML1.0 file is hyper-deci-VRML1-nonormals.wrl.  This file does not have the normal vectors calculated.  You should be able to notice the significant difference in shading.

The four wrl files above are stored in the sub-directory WRL.  If your web browser has an appropriate plug-in installed, you should be able to click on the links above to view the wrl files.  Otherwise, you can view any of the wrl files by typing, e.g., under Linux:
vrmlview hyper-VRML1.wrl