Multilayer Materials

Multilayer materials allow you to combine effects which previously required the use of labels. Thus you can easily create metallic and pearlescent paints, carbon fiber, varnished wood, perforated leather, etc., which can be assigned directly as a single material.

The technique to assign a multilayer material on a surface is identical to that of a single material.

Layers are created one after another in the upper part of the Materials editor.

When a layer is created, using the New Layer button, you have the choice of three different types: diffuse layer, specular layer, illumination layer, flakes layer.

The order of the layers is important: if a completely opaque layer is on top, it will mask all layers beneath it. You can move a layer in the list by clicking and dragging.

Each type of layer is represented by a different icon: a top-lit ball for a diffuse layer, a luminous ball for an illumination layer and a mirror-finish ball for a reflective layer.

Types of Layers: Diffuse Layer

In general this is the first layer created, the one giving the basic color. For a standard material, the parameters are given under the diffuse tab. The same semi-transparency options as those for the standard materials apply.

In fact there are only two differences: the illumination parameter has disappeared (an illumination layer must now be created) and the diffuse grain is incorporated directly.

The diffuse layer parameters operate in the same way as those of the diffuse tab for the standard material.

Mixing the diffuse layer is standard: if the diffuse layer uses a see-through image, the layer underneath is shown in proportion through it.

Diffuse layers can accept a video texture as a Color Map.

Types of Layers: Specular Layer

In the same way that a diffuse layer incorporates its own diffuse grain, a specular layer incorporates its own specular grain. This approach provides better hierarchy of the layer parameters and provides more options. The specular layer is parameterized in the same way as the parameters under the reflection tab for the standard material.

A specular layer operates in additive mode: the reflection is added to the combination of lower layers, but provides overall filtering of the lower layers and variable attenuation according to the Fresnel reflection. If the Transmission attenuation option is ticked, then some of the reflected light on the surface is not transmitted to the lower layers, making the light behave realistically.

The Roughness map is a grayscale texture where the black corresponds to a roughness of 0 (smooth) and white corresponds to a roughness value of the material.

On the other hand, the Gloss map is a grayscale texture where the black corresponds to ta value of the material roughness and the white corresponds to a roughness of 0 (smooth).

You will find in the accordion menu named Mapping the following parameters Allow repeat in U and Allow repeat in V that allow you to choose to repeat the texture in U and/or V.

By checking the Mirrored check box you can reflect the texture in U and/or V.

Types of Layers: Illumination Layer

This layer combines the parameters previously distributed in the standard material under the diffuse and reflection tabs.

The illumination color is found in the standard material under the diffuse tab and allows a certain luminosity to be generally added to the material. The brightness may be greater than 1.

The velvet effect in the standard material is found under the reflection tab, but also acts as a light addition, this time depending on the viewing angle on the surface. The added luminosity is given by a gradient ramp multiplied by a specifiable factor, which may be greater than 1.

If a modulation image is activated, it filters the modulation color on the surface. If the velvet effect is used, ticking the Use modulation image box modulates the effect so as to provide a more realistic appearance.

Note that an illumination layer includes a grain, which affects only the velvet effect if activated. The grain reinforces the realism, especially of fabrics.

An illumination layer operates in additive mode: its contribution is added to the lower layers.

For more complex materials, nothing prevents you from using several layers of the same type. For example, a 3D open mesh fabric may use one diffuse layer for the lower textile and another diffuse layer, made visible using the transparency effect, for the top layer.

If the underside is glossy, then the latter diffuse layer will be on the specular layer of the lower layer. The organization of the material would thus be:

• Specular layer, upper textile
• Diffuse layer, upper textile
• Specular layer, lower textile
• Diffuse layer, lower textile

If you also want to use the velvet effect because the surface of the fabric is partly soft or textured, inserting an illumination at the right place will do the job:

• Specular layer, upper textile
• Illumination layer, upper textile
• Diffuse layer, upper textile
• Specular layer, lower textile
• Diffuse layer, lower textile

Flakes layer

The flakes layer is particularly useful when you want to reproduce, for example, the effect of glittering paint of Car Paint type like on a car body.

The Car Paint type material is a multilayer material (diffuse, specular and flakes). The flakes layer is generated using the Flakes Layer Editor.
To add a flakes layer, click Add Flakes Layer.

All flakes can have the same color, or follow a distribution given by a color palette available in the Flakes Color Editor. See the Multiple Colors parameter.
Random variations of the same color are possible between the flakes via the L +/- (Luminance ) or a +/- or b +/- (chrominance) parameters which define a standard deviation according to the Normal distribution.

Flakes can also vary in size thanks to the Size parameter.The Orientation is expressed in degree with more or less variations via the standard deviation +/- of the Normal distribution.

The visibility of the flakes can be dimmed according to their angle which is defined by the combination of a depth value and the texture of the Normal distribution.

The Sides parameter defines the number of sides of a flake (from 3 to 8 sides): eg. triangle, square, octagon.

The Texture Size parameter sets the size of the texture in pixels.

• The higher the texture size, the better the definition with longer generation time and more data to store.
• The smaller the texture size, the less good is the definition with a short build time and less data to store. The greater the probability of seeing pattern repetitions of textures.

The Seed parameter is used to generate a different texture from the same parameters. To avoid the redundancy of a texture the Seed parameter randomly generates a new texture according to a value.

You have the option to generate a texture with glitter randomly distributed on the texture Flakes Distribution > Random or evenly distributed Flakes Distribution > Even.
Choose the flakes distribution according to the result you want. For a more realistic rendering of the generated texture, the random distribution of flakes is recommended for a texture composed of a lot of flakes.

If you enable the Update automatically textures parameter, after each change to the flake texture settings, the layer will automatically update. If instead the box has not been checked, which is the case by default, it is necessary to click on this icon after each modification of the texture parameters.

The features available in the Reflexion Color, Fresnel, and Roughness accordion menus are described in their dedicated section.

The features in the Advanced accordion menu are explained in the specular layer section above in this chapter.

Enhanced Relief

Multilayer materials using a height map can be rendered with textural relief that is even more realistic. This option offers an enhanced perception of depth thanks to the way it handles parallax.

The use of enhanced relief is best suited to contexts where a standard material uses a texture that requires more visual depth than that which can be rendered using bump maps in diffuse and specular layers.

The Relief tab gives access to settings that provide a rendering which, while robustly real-time, requires more time to calculate. It is therefore recommended to use this option where appropriate, without overloading a scene.

Enabling Enhanced Relief

Enhanced relief must be enabled:

• globally for the material in the Relief tab,
• then for the required layers in the Layers tab. By default, it is disabled in all layers.

Enable enhanced relief in the Bump tab of the Materials editor for a standard material:

1. Tick the Relief checkbox in the Depth section and provide a value for the depth.
2. Assign a texture as a Bump Map.

Switch to the Layer tab:

3. For the layer or layers that should use enhanced relief, tick the Use enhanced relief checkbox in the Bump section.

Disabling one of these elements will also disable the enhanced relief.

Settings

The settings for enhanced relief are found in the Relief tab of the Materials editor:

Setting	Description
Relief depth	The depth defines the distance between the white and the black zones of the height map. The white zones are aligned on the mesh of the surface. Because the perceived depth of the map's black zones is set using this parameter, the height map should make use of the full range of elevation available, from white to black. When this is not possible, make sure that the map's maximum elevation will be aligned with the modeled surface, that is, that it is represented in white on the height map. A negative value will invert the depth of the texture: depth is rendered as rising from the surface instead of as incisions carved into the surface. While possible, this rendering is not optimal and is not recommended. Values between 0 and 10 are usually sufficient. Using values that are too high can create visual deformations when viewing surfaces at low angles or when viewing curved surfaces.
Height map	A height map is required. This map is a black and white texture that is assigned to the material. The texture to be used as a height map can be square or rectangular. The height and the width of the texture in pixels must both be powers of two. Although Patchwork 3D Design will resize height maps whose dimensions are not useable, choosing textures with dimensions that are powers of two is highly recommended in order to preserve the particularities of the height map.
Dimensions and Transformation of the bump map	These settings are modifiable as normal in order to adjust the dimensions, the orientation, and the position of the height map on the surface.