RENDER BENDER

David Spencer looks at Clares' new 3D ray tracing package.

Anyone who experimented with Roger Wilson's ray tracing program from last month's RISC User will appreciate how powerful a technique it is. However, modifying the program for different images is far from simple. Render Bender from Clares is a new package designed to take the pain out of ray tracing and enable advanced effects to be achieved with relative ease. For anyone who did not read last month's article, ray tracing is basically a brute force technique for determining the appearance of a 3D image made up of solid objects. The technique works by considering every pixel on the screen, and conceptually tracing rays of light back around all the objects until they reach the original light source.

CREATING A SCENE

Before continuing, I must make one thing clear - Render Bender is not, and does not claim to be, a drawing or painting package. In fact, Render Bender offers no facilities for interactively editing a picture on screen. Instead, Render Bender is designed solely for the creation and animation of scenes consisting of geometric objects.

The process of creating and displaying an animated sequence consists of several stages:

1. The objects making up the scene are defined using a special programming language, together with the changes from frame to frame (if any) to produce an animated sequence.

2. The text description of the scene is compiled into Render Bender's internal format.

3. The individual frames are ray traced according to a number of options which may be set up.

4. The resultant frames are compressed using a deltafile method, and a display program incorporated.

5. Finally, the completed sequence is displayed.

RUNNING RENDER BENDER

When you start the Render Bender disc you are presented with a very swish title screen consisting of a rotating gold coin. This gives way to an equally impressive selection screen which allows you to choose between the editor and ray tracer program, or the deltafile animator. Both of these screens were created using the package itself.

The stages of producing an animation sequence are performed by two independent parts of the program, linked by a selection screen. The first of these is the editor and ray tracer. This allows you to create a scene with the scene description language, and ray trace it to create a number of frames.

THE SCENE DESCRIPTION LANGUAGE

The scene description language is the key to creating a picture. The format is entirely text-based, and consists of a series of keywords followed by a number of qualifiers and parameters, all of which must be separated by commas. There are basically three types of commands, these being used to position light sources, the viewer, and any objects. All positions are specified in 3-space as X, Y and Z co-ordinates, with the origin effectively at the centre of the image. The view point for the scene is given by the viewer's position, and either the point they are looking at or the direction they are looking in. There are three possible types of light source - a ray, a point source, and a spotlight, and these can be mixed at will in a scene. For a spotlight you can control not only the direction of the beam, but also the angle through which it spreads. Objects in the scene can be chosen from pyramids, boxes, tubes, discs spheres and polygons, and are specified in terms of their position, dimensions and orientation. Additionally, each object can be given a colour, and a surface attribute which determines whether the it is Shiny, mirror-like, metallic, opaque or bulb-like. (A bulb appears brilliant white, regardless of the light falling on it).

Animation is achieved by incorporating variables in the definitions. The ray tracer will automatically update these variables in the specified way between frames.

Once a scene description has been written, it has to be compiled from within the editor. This only takes a few second, and then the scene is ready to be ray traced. Before this is done, a number of parameters need to be set up. For example, you can change the floor pattern, floor scaling, sky colour, viewing lens, opacity of opaque objects, the refractive index of objects that transmit light, and shadowing. You can also select whether to ray trace in mode 13 or 15, and whether to scale the picture for a faster preview. The actual ray tracing can be quite time consuming. For a complex, full screen image in mode 15 with shadowing, it can take about an hour a frame. In other words, a fifty frame sequence could take two days!

A single ray traced picture can be exported directly from the ray tracer. However, an animation sequence must be processed by the deltafile animator. This part of Render Bender takes a sequence of picture files, and compresses them to produce a final sequence file. The order in which the frames are displayed is also determined at this point. The final sequence can either be displayed directly from within Render Bender, or saved and played back separately using a simple Basic program.

PRESENTATION

Render Bender is supplied in an A4 size opening box, with the two discs slotted into the inside cover, and the manual recessed into the box. The box is printed in full colour and is very eye catching. This is a major departure from the 'video case' style box previously used by Clares, which I personally thought was always very drab. Also gone are the familiar Clares' disc labels, which have now been replaced by a more attractive design. My only quibble about the new presentation is that the review copy arrived somewhat squashed. Hopefully, Clares will improve their packaging to prevent this.

DOCUMENTATION

The Render Bender manual has not escaped Clares revamp either. It is an A5 sized book, about 80 pages long, and printed on high quality paper with glossy full colour covers. The cheap looking plastic comb binding has been replaced with genuine Wire-O binding. The manual is properly typeset, and is laid out in such a way as to make it very impressive and easy to read. There are plenty of clear illustrations, and several direct screen dumps.

The manual starts off with a brief overview of the package and the principle of ray tracing, and then continues with an exhaustive explanation of how to start Render Bender and how to install it onto a hard disc. Render Bender is fully RISC OS compatible, and instructions are given for starting it from the Desktop.

The next section covers the use of the Editor and Ray tracer. This is presented in such a way that a first-time user can get the system up and running without getting bogged down in all the various controls. The final main section covers the Animator, and is again easy to follow for the first-time user. This section also explains how to display animated sequences without Render Bender being present, and how to use the Animator to animate screens generated by other packages.

Two appendices explain the syntax of the all-important scene description language, and any possible errors that may occur while running Render Bender. The manual is rounded off with a comprehensive index. The only fault I could find with the manual is the lack of a detailed explanation of ray tracing. Admittedly, it does point out that this would require an entire book, but Clares could still have recommended one. Personally, I like the book suggested last month.

CONCLUSION

Clares have once again come up with a professional product, and also one which does not suffer from the problem of highly graphical, but totally confusing, icons - a criticism of Clares' products in the past. There is no doubt that Render Bender is excellent at performing its function, and is a very well thought out package. It ensures that all that is needed to produce stunning animations is a good imagination. But what use is it? The Archimedes has now been around for nearly two years, and the thrills of stunning images and animation sequences are, I feel, rapidly subsiding. I don't think many people will buy Render Bender just to draw pretty pictures and sit looking at them for hours, especially at £80.
Product:Render Bender
Supplier:Clares Micro Supplies,
 98 Middlewich Road,
 Rudheath, Northwich,
 Cheshire CW9 7DA.
 Tel. (0606) 48512
Price:£79.95 inclusive

This month's magazine disc contains some sample frames produced using Render Bender.