6.19.2. Setting Up Materials

A model’s textures are listed in the Materials panel. This is displayed during import and can be accessed again at any time after import by clicking the cog icon next to the 3D model in the Media panel, or right-clicking the model and choosing Properties from its menu.

The appearance of a 3D model in your scene can be drastically altered using the materials options. Models will often have multiple materials, representing different parts of the model. The glass in a car’s windows will be a separate material to the metal on the doors, for example. For realistic results we recommend setting up each material.

*Once you’ve got a model perfectly set up, you can always save it out to a project file which can be used as a template in the future, saving time.

Selecting a material in the list will highlight it with a red mesh in the preview, so that you can see precisely which part of the model you are adjusting. Each material will have the following controls. More detailed explanations of these controls and their functions can be found below, on this page.

• Diffuse Map: A Diffuse Map defines the primary texture on your model. The image is mapped onto the model’s surface, so the details in the map appear to be painted onto the model’s surface. Click the folder icon to open a browser and select a diffuse map image. Click the X to remove the image.
• Specular Map: A Specular Map defines how shiny different areas within the material will be. With no map, the entire material will be consistently shiny. Click the folder icon to open a browser and select a diffuse map image. Click the X to remove the image.
• Normal Map: Normal Maps are used to increase visual detail of a model without negatively impacting performance. They must be generated by 3D modeling software. Click the folder icon to open a browser and select a diffuse map image. Click the X to remove the image.
• Bump Map: Bump Maps perform a similar function to Normal Maps, but in a simplified way, using greyscale to indicate bump height. Click the folder icon to open a browser and select a diffuse map image. Click the X to remove the image.
• Max Bump Depth: Bump maps are greyscale, with pure black areas being the lowest, and pure white areas being the highest. This setting defines the height of the white areas, then all gray values are mapped into the difference between the black height (the model’s actual surface) and the white height.
• Diffuse Color: Alters the base color of the material under a point, spot or direction light. The luminance of this color determines the brightness of the diffuse texture map. Click the swatch to open a color picker and chose any color. You can also use the eyedropper to select a color from the Preview, or manually enter the RGB values for your desired color.
• Specular Color: Determines the color used for the material’s specular highlights. Specular highlights are only visible if there is a 3D light source in the scene. Click the swatch to open a color picker and chose any color. You can also use the eyedropper to select a color from the Preview, or manually enter the RGB values for your desired color.
• Ambient Color: Defines the color of the material under an ambient light source. Click the swatch to open a color picker and chose any color. You can also use the eyedropper to select a color from the Preview, or manually enter the RGB values for your desired color.
• Emissive Color: The color of the material regardless of the lighting setup. Even when the model is unlit or shadowed, it will still emit this color. This is useful for simulating light sources, such as neon objects or lights on a vehicle. Click the swatch to open a color picker and chose any color. You can also use the eyedropper to select a color from the Preview, or manually enter the RGB values for your desired color.
• Illumination Model: There are two illumination models available, to better simulate different physical materials.
  • Phong: Phong is effective for very smooth surfaces with a single specular highlight, such as plastics or paint.
    • Shininess: Adjusts how glossy the material is, and the size of the specular highlight.
  • Cook-Torrance: Cook-Torrance is a Physically Based Renderer more suitable for metals, with a rougher surface that distributes the light less evenly.
    • Fresnel: Adjusts reflectivity based on the angle of the surface relative to the viewer. The more perpendicular the viewing angle, the more reflective the surface. The values here determine the range of reflectivity, for each of the color channels. The Menu of metal types offers convenient presets for different common metals.
    • Roughness: Adjusts how rough the surface of the metal is, and thus how much of the light is reflected in a diffuse fashion, rather than being reflected specularly.
• Diffuse Reflectivity: Diffuse reflectivity refers to light being reflected in all directions. It does not produce a direct reflection, but causes the object to be illuminated by surrounding objects.
• Specular Reflectivity: Specular reflectivity is what we normally think of when we talk about reflections – seeing a visible reflection of an object on the surface of another object. Increasing specular reflectivity allows the material to reflect nearly objects in the 3D space.
• Reflection Mode: Select the mode used to calculate the reflectivity.
  • Spherical: Uses a spherical reflection.
  • Planar: Uses planar reflections.
• Index of Refraction: Refraction occurs when light is deflected while passing through a semi-transparent object, causing a vertically inverted version of the scene to be reflected onto the surface of the material. The Index of Refraction sets the amount of refraction, which differs depending on the density of the material the light is passing through. Water has a refraction index of 1.7 while glass typically starts about 1.55, for example.
• Refraction Amount: This value defines the visibility of the refraction.

Texture Maps

At the top of the controls for each material are four texture map slots, for Diffuse, Specular, Normal and Bump maps. These are used to add detail and color to the 3D geometry.

Compare the difference between an untextured model in the first image, and the same model with textures and materials set up, in the second image:

Most 3D models have been designed with textures. HitFilm will attempt to import textures automatically during import, if they are located in the same folder as the 3D file. If textures are not found automatically or if you want to change a texture, you can locate a new one using the folder icon. You can remove a texture from a slot using the X button.

Diffuse Map

The diffuse map is used to add surface detail and color to the model. Here is an example of a helicopter, with the diffuse map providing dirt detail on the hull as well as lettering:

The image file for the diffuse map looks like this:

Textures are not made inside HitFilm. Instead, they are produced when the 3D model is designed and created. However, you can customize textures using any normal image editor, and changes made can be then re-applied in HitFilm.

Specular Map

Specular highlights are created by your lighting setup. By default all surfaces on the model are equally likely to receive specular highlights. Sometimes, however, you may want to restrict specularity based on the material – for example, if you have a normally shiny surface (such as polished metal) covered in dirt and scratches, you will want to restrict the specularity only to the clean areas. This can be achieved using a specular map.

Observe the helicopter in the first image, without a specular map, and compare it to the second image, with a specular map applied:

In the above example the specular highlight has been made blue and more extreme, so as to illustrate the point. Ordinarily you would opt for a subtler appearance. In the first image, where no specular map is used, note how the specular highlight is bright along the entire length of the helicopter, including over the UNITED STATES ARMY text. In the second image, note how the specularity has been restricted. Dirtier areas of the helicopter are less reflective. The UNITED STATES ARMY text is now visible and is not creating highlights – as if the black paint of the text is preventing it. Using a specular map can drastically improve the realism of your 3D models.

3D models are usually provided with a specular map, but they can also be created by hand. They are greyscale images, with black areas representing non-specular areas and white areas representing high specularity. The specular map for this helicopter is very simple:

The specular map slot also restricts the behavior of the reflectivity options, detailed below.

Normal Maps & Bump Maps

Normal Maps are hugely powerful textures which can be used to add the appearance of additional 3D detail to a model, without actually increasing its polycount. Normal maps are used to create detailed models without negatively impacting performance.

The smooth 3D sphere in the first image has no surface detail at all. By applying a normal map, we get the second image:

The sphere model now appears to have substantial surface detail. However, it is still the same smooth sphere. The illusion of surface detail is being created entirely by the normal map. The huge benefit is that the model is still very simple, which keeps rendering times low.

There are restrictions to how normal maps function. If you move your camera very close it will become apparent that the detail is texture-based. Similarly, viewing the model from an oblique angle can reveal that the surface detail is only an illusion. And while the normal mapped surface reacts to the position of 3D lights for illumination and shading, normal maps won’t cast actual 3D shadows. Normal maps are therefore best used for subtle, fine surface detail, while major features are represented by actual geometry.

Bump Maps perform a similar task to normal maps but using a different, less sophisticated technique. Bump maps can be created by hand much like a specular map, as they are greyscale images with white representing maximum height and black representing minimum height. Normal maps have to be generated from by 3D modeling software and the textures include information for X, Y and Z vectors.

A common workflow would be to produce a high poly model first, then generate a normal map which can be applied to a low poly version. This retains the illusion of fine detail while keeping fast performance.

Because bump maps are inherently relative, with no actual defined height, you can adjust the scale of bump mapping using the Max Bump Depth property. This does not affect normal maps.

Lighting Colors

The various color properties are used to set up the default colors for the material. These combine with the texture maps and your lighting setup.

• Diffuse Color: Alters the base color of the material under a point, spot or direction light. The luminance of this color determines the brightness of the diffuse texture map.
• Specular Color: Determines the color used for the material’s specular highlights. Specular highlights are only visible if there is a 3D light source in the scene.
• Ambient Color: Defines the color of the material under an ambient light source.
• Emissive Color: The color of the material regardless of the lighting setup. Even when the model is unlit or shadowed, it will still emit this color. This is useful for simulating light sources, such as neon objects or lights on a vehicle.

Illumination Model

There are two illumination models available for materials: Phong and Cook-Torrance. In general, Phong is more suitable for plastics with a single specular highlight, while Cook-Torrance is more suitable for metals with a rougher surface that distributes the light less evenly.

*Note that the specular highlight for both illumination models is determined by the specular color, described above. A specular map can also be used to restrict the specular highlights of a material.

Phong

Phong generates a defined highlight similar to plastic materials. Light bounces off the surface evenly. This model has less control than Cook-Torrance.

The color of the highlight is determined by the specular color.

A small Shininess will generate a large highlight, as seen here:

A larger shininess value will generate a smaller, sharper highlight:

Cook-Torrance

This illumination model provides greater control and is more suitable for metal surfaces. Bounced light is scattered across the surface, as if reflecting off multiple ‘microfacets’, rather than a focused, singular bounce as with Phong.

The Fresnel determines the scattering of light. Several metal presets are provided to make it easier to choose a suitable material.

Roughness determines the spread of the specular highlight. A low roughness creates a defined, sharp highlight, while a high roughness diffuses the specular highlight across the surface, moving towards a more matte material.

Specular Reflectance adjusts the intensity of the specular highlight.

In this example a copper fresnel is being used to generate a more realistic metallic appearance, compared to the Phong images above:

Here is the same setup in a more natural lighting scenario:

Reflectivity

There are two types of reflectivity. Specular reflectivity is what we normally think of when we talk about reflections – seeing a visible reflection of an object in the surface of another. Diffuse reflectivity doesn’t produce a direct reflection but causes the object to be illuminated by surrounding objects.

Here is an example image with a single light source and no reflectivity:

The overall lighting in the above image is unconvincing, because the skull is not being illuminated by it surroundings. While the blue wall and grey floor are not directly emitting light, they should nevertheless be bouncing light.

Here is the same shot with diffuse reflectivity turned on, and no other changes:

This time the skull sits far more naturally in the scene. It is brighter and is receiving diffuse blue light from the back wall. This still only uses a single light source, but the overall lighting impression is far more realistic. The diffuse reflectivity technique is subtle and hugely powerful – for very little effort you can achieve much more convincing lighting.

Here is the same scene using specular reflectivity instead of diffuse:

The result is very different. The reflections are very sharp and defined, as if the skull were a shiny chrome material.

Here is a more extreme example, using the same settings but a different background wall:

And the same background again, but with a diffuse reflectivity setup:

You can, of course, combine the two, which is what you will normally want. That’s how the copper skull was created, using a mixture of diffuse and specular reflectivity:

The amount of diffuse and specular reflectivity can be adjusted per material.

You can also use an environment map image for reflectivity, in addition to the actual 3D scene. An environment map is usually a panoramic, wrap-around image representing a particular location. While this is not as accurate as reflecting the actual 3D scene, it is often more convenient. For example, if you are compositing an object into a live action plate, you are more likely to have a panoramic image of the location than a full 3D recreation.

A 3D layer can be assigned a single environment map. This is set in the material properties of the layer on the timeline. See 3D Objects on the Timeline for more information.

Refraction

Refraction occurs when light is deflected while passing through a semi-transprent object. In HitFilm refraction causes a vertically inverted version of the scene to be visible on the surface of the material.

As with reflectivity, refraction can also use the 3D model layer’s environment map. See 3D Objects on the Timeline for more information.

The Index of Refraction sets the amount of refraction, which differs depending on the density of the material the light is passing through. Water has a refraction index of 1.7 while glass typically starts about 1.55, for example.

The Refraction Amount determines the visibility of the refraction.

Here is an example of the skull object set up to look more like crystal:

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