Chapter 5

Material Construction

Overview

The Material Editor within 3dsmax is capable of creating both simple and very complex materials. In addition to the standard bitmap type of material there are many procedural material types available to the user.

There are many types of ‘base’ materials that are used to texture models within 3dsmax but two of them – ‘standard’ and ‘multi/sub-object’ are generally the main materials used. The ‘standard’ type is applied to a whole object and consists of one material, whilst the ‘multi/sub-object’ type is used to apply different materials to selections of faces within a model.

3dsmax also has the ability to UV map an object or selection of faces with up to 99 different mapping channels, allowing textures to be applied over the top of each other with different mapping coordinates i.e. a poster on a wall, or dirt over a street.

Materials can also be nested within each other i.e. a noise colour channel can be fed by another noise map giving a greater detail to the noise. With the ability to add masks, mixes, blends, composites etc. the variations in materials is almost infinite.

Vertex Channel Dirt

With the model of Amarna being a city, it was necessary for it to look lived in and thought was given as to how this could be accomplished within a short timeframe. The ground plane needed to show paths and various routes the inhabitants of the city may have walked daily.

One method which seemed to do just this was created by using the vertex colour channel within the actual geometry itself. When an object is created within 3dsmax the vertices not only hold the geometry together but also have the ability to store colour information. This ‘vertex colour channel’ can be used in real time applications to recreate shadows in the scene or complex lighting such as radiosity solutions. In the case of Amarna the ‘vertex colour channel’ was to be used as a ‘dirt’ mask, enabling ‘dust tracks’ to show through grass.

To enable this to work properly, the vertex colours need to be changed to varying shades from white to grey; this was implemented in a two stage process. The first stage was to use a ‘quickdirt’ maxscript, which analyses the geometry for creases, corners, crevasse’s etc. where dirt would lay, and then change the associated vertex colours to suite. This gave a very quick way of creating a more natural worn look to the model. The second stage was to refine the vertex colours by hand painting some of the geometry using the vertex paint modifier, this allowed tracks and walkways to be added where needed.

Using vertex colours in this way is only really effective if you have enough vertices within the geometry to give a decent amount of detail.

When the geometry had been processed, a mask material, using the vertex colour map as the source for the mask, was created and applied to the object. This method was used for walls, roofs, monuments, etc in addition to the ground.

Unfortunately, although this method gave good results, when the scene was rendered with the lighting system, the render time per frame trebled giving times in excess of 1.5 hours during some parts of the animation. This was totally unacceptable and more ‘traditional’ methods had to be employed.

Building materials

The model consists of very definite areas based on class. The Royal buildings and temples used cleaner materials with hieroglyphic texts’, the middle class used a slightly worn version of this, with the suburbs being more run down.

As a result of the problems with the vertex colour material it was necessary to create these textures, with varying degrees of dirt and wear & tear, manually using Photoshop.

To create the main textures for the Royal buildings, images were scanned into Photoshop from the book ‘The Monuments of Egypt’, Gillispie & Dewachter (1987), and edited into various wall freezes. The textures were given some ‘dodge & burn’ treatment to give some wear & tear to parts, especially the base of the walls where sand would collect. The trims around the tops of the pylons and lintels used various types of strip patterns in keeping with the period. Care had to be taken with the hieroglyphs used, as the Pharaoh had outlawed depictions of the other deities. As the rooftops would have been unseen and unattended, a general sand texture was used.

Middle Class buildings used a modified version of the Royal texture set, but included more brick work and were given more dirt & grime. The water holes were given a semi transparent ‘water’ texture.

The Suburbs were textured using period building images manipulated within Photoshop. These images were made to tile by using the ‘offset’ filter and cloning other parts of the image. The final textures were given a ‘dirt’ treatment, again in Photoshop, and applied to the building sides within the suburbs.

Ground based textures

After the vertex based method was scrapped, the only reasonable approach left was to apply a standard mask material to the ground. The ground based materials had to have detail for close up shots, whilst still covering a large area without any visible tiling. In addition the ground had to include tracks and walkways. Due to the overall physical size of the model, hi-resolution textures would have been ideal if it had not been for the massive memory overhead this placed on rendering. This meant that tiled textures were needed to be used wherever possible and higher resolution textures only when absolutely needed.

To enable this to work successfully the landscape portions of the model were split into manageable sections and textured separately. The ‘base’ material consisted of a grass portion and a dirt/sand portion mixed together by a mask. A mask was created for each landscape section by taking screen grabs of each landscape section in wireframe, and painting over this within Photoshop to create a greyscale image of tracks and walkways.

The ‘dirt/sand’ portion of the texture was created from various photographs of actual sand and dirt and made to tile using the offset/clone method. The grass was created by nesting procedural noise maps within each other and various tints of green and orange/yellow for the colour channels. The advantage of using procedural noise was that the detail would be present on close viewing, with large noise working for distance shots. A variation of the noise was then used as a bump map to add to the ground realism.

Any seams between landscape sections were dealt with in the grass portion of the material. As the grass was constructed from procedural textures, the material was set to use world mapping, and in doing so flowed between the landscape sections.

This combination of tiled textures, procedural noise and higher resolution masks proved to be quite effective.

Miscellaneous Textures

There were many other objects that needed texturing within the various animated sequences, including the bugs, ships, Anubis, the priestess and Akhenaten. The methods used for these models are fairly standard practise now in 3d modelling and as such will not be further elaborated on in this document.

 
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