Rayfront Materials

Once you have imported materials into Rayfront it is necessary to assign materials to the surfaces to be able to render a picture. Because the program is calculating the light reflected off or transmitted / refracted through objects it needs to know the reflection / transmission / refraction properties of ALL surfaces in the model. Fortunately this is a simple exercise to do for lighting studies. We need to assign glass where there is glass and then use the standard lighting study versions of "white" in order to assign appropriate surfaces to our daylight model. This is reflectivity of 0.7 on the ceiling, 0.5 on the walls and 0.3 on the floor. We typically assign a little colour to the glass in order to be able to see it. But we try to keep the total transmissivity at 0.85.

First we click the assign/edit materials button:

Materials:
The window that opens looks like this (except there are no materials defined when we first open it and all the objects in the top left hand corner have "Default material" attached.

Click the <library> button to select a library from which to "add to selection" some materials that will appear in the top right window for later attaching to objects ion the building.

The libraries that are available are: archicad, greys, metals, and then a bunch of in-house materials including simple colours, a range of glasses of different transparency, real materials, simple colour models of materials, translucent materials and "wood" colours.

Patterns:

In the very top corner of the assign/edit materials box there is a pull-down menu permitting one to select between material definitions which are basically colour, reflectance and transmissivity andpatterns which are systematic variations in colour across a surface such as black and white tiles:

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Textures:

Textures can also be found as a third option in the drop down menu top right of the assign/edit materialswindow. They are variations in surface such as dustiness and a greater degree of roughness than can be defined in the simple materials.

As can be seen by the matrix arrangement of the left hand area of the assign/edit materials window, each object in a building can be assigned a combination of a material definiton, a pattern definition and a texture definition.

<NEW>

At bottom right of the assign/edit window there are a number of buttons that help manage and extend this material definition process. First is the ability to create a "New" definition of a material, pattern or texture. Then we have the ability to Clone an existing material, pattern or texture in order to create another. Or we could <edit> and existing definition, delete a definition form our current file and finally to <Store> our set of materials, patterns or textures in a new project specific library.

<LIBRARIES>

The publishers of the program Design Workshop have published the Radiance Materials notes of Kevin Matthews. His notes and notes from Veronika Summerauer and colleagues at ETHZ Switzerland and Matiu Carr of Auckland University all done in the early 1990's form the basis for the following materials definitions.

It should be remembered that unlike other computer graphics programs Radiance, the rendering engine that Rayfront provides a front end to, uses procedural materials and textures, rather than pasting innappropriate pictures onto surfaces to provide the appearance of materials. Radiance has three different levels of material creation:

1. the material physics itself using standard Radiance material definitions such as "glass", "plastic", "metal", trans(lucent) etc to define the colour and surface finish, raflectivity, surface roughness (diffusion) and transmissivity.
2. the surface patterns defined by functions like "brightfunc" which modify the colour appearance systematically so that marbling and wood grain may be successfully modelled by formula
3. the surface textures defined by functions like "texfunc" which modify the surface roughness systematically so that corrugations, water ripples and even brick grout may be represented by formula..

A truly successful material is often a combination of these three. The following notes refer to the Matthews / ETHZ materials and functions and guide the user on the combinations that may be successful.

TEXTURES

Note: the materials often have to be rotated to match the orientation of the face that they are to be applied to. Thus, they have transformations (Radiance function xform) applied after they have been defined. Essentially when defined they are orientated orthogonally in the xy plane. Rotations are needed about the x, y and z axis and scale factors to match the scale of the material to the scale of the object (so a wall is not one brick long and two bricks high, say!). If you edit the material definition itself you gain access to these -rx -ry -rz and -s operations. Remember you need to be viewing the scene in the interactive viewer with the irradiance button (not radiance)

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Shared Dusty Functions: many of the materials use these "dusty" functions to apply the Radiance dirt.cal function to give a certain 'natural', noisy texture.
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dusty_wide texture (scale 2, depth 0.25)
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dusty_med texture (scale 1, depth 0.25)
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dusty_tight (scale 0.2, depth 0.25)
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dusty_tight_deep (scale 0.2, depth 0.4)
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