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Materials, Lighting, and Rendering

BIM for Architecture, Engineering, and Construction Curriculum

Overview

In this lesson, students explore how to use Autodesk® Revit® software to adjust the appearance of the building model elements that appear in their 2D and 3D views. They will learn how to:

  • Assign materials to model elements through object styles, type properties, and instance properties.
  • Adjust the render appearance of materials to display realistic views.
  • Render views to create realistic views in daylight and artificial lighting conditions.

Assigning Materials to Model Elements

You can assign materials to the elements in a building model to accurately display their appearance in shaded and rendered views. All elements in a building model have a material—either a default material based on the object category or a specific material that has been assigned through the element’s type or instance properties. Materials are assigned to elements using this hierarchy:

  • Defaults—using default materials, which typically display a solid gray color.
  • Object style—using the materials assigned to an object category or subcategory.
  • Type properties—using the materials assigned to all elements of the same type in the family’s type properties.
  • Instance properties—using the materials assigned to a single element through its instance properties.

If an element has properties that assign a material at a higher level in this hierarchy, lower-level settings will be overridden. For example, a furniture element that has materials assigned through its type properties will use those materials, rather than the default material assigned to the furniture category.

Changing Material Display and Render Appearance

Revit software includes an extensive library of predefined materials and rendering appearances, and you can edit the existing materials or duplicate them to create new ones as needed for your design.

Use the Material tool in the Manage tab to edit existing materials, create new ones, and specify how the materials will be displayed in views. You can set these options for hidden line, shaded, and consistent color views:

  • Shading color
  • Transparency
  • Surface patterns (for cut and uncut surfaces)

You can also assign a render appearance to each of the materials that will be displayed:

  • Views set to use the realistic visual style.
  • Photorealistic views created using Revit software’s rendering tools (which we will learn about in the next lesson).

To change a material’s render appearance, open the Materials dialog box, then switch to the Render Appearance tab, where you can browse the library of render appearances by material type or search to find specific items. You can:

  • Replace the current render appearance by choosing a new one from the library.
  • Adjust the settings to change or fine-tune the current render appearance.

Creating Exterior Rendered Views

Autodesk Revit software can render photorealistic views that accurately portray the materials selected as well as the effect of lighting and shadows. Rendered views are useful for presenting your design to clients and other reviewers who want to preview the appearance of the finished building.


Figure 1.7.1. - Shaded and rendered images of the same view

You can render any 3D orthogonal or perspective view to create a photorealistic image.

Open the Rendering dialog box by clicking the Show Rendering Dialog button in the View Control Bar, where you can specify these settings:

  • Quality—the overall quality of the rendered image, ranging from Draft to Presentation quality. Higher-quality images are more realistic, but take much longer to produce.
  • Output resolution—the number of dots per inch (DPI) to produce in the rendered image. Higher-resolution images are useful when they will be blown up or printed at high quality, but also take longer to produce because more data is computed.
  • Lighting scheme—the sources of light that will provide illumination. For exterior renderings, the sun is typically the primary light source.
  • Background—the appearance of the sky. If you prefer, you can specify a background image rather than using Revit software’s automatically generated sky.

The rendering settings chosen has a very dramatic effect on the amount of time required to render a view. For this reason, it is typically wise to:

  • Start by testing your renderings at draft quality to see the results quickly.
  • Use these draft renderings to identify any elements that need to be adjusted or corrected (for example, materials that are not assigned properly).
  • Create another rendering at draft or low quality to confirm the adjustments. You can limit the region rendered to focus on the area where these elements appear, rather than rendering the entire view.

Creating Interior and Nighttime Rendered Views

You can also create photorealistic renderings of interior 3D views to see materials selected and explore lighting effects. Interior views can be rendered to show the effect of daylight transmitted through openings, windows, and curtain walls. But, depending on the sun’s position and time of day, you will often need to supplement the sunlight with artificial light sources (for example, lamps, surface fixtures, and recessed lights).

You can use artificial lights to:

  • Explore the effects of using different lighting schemes and fixtures to illuminate a space.
  • Create evening or nighttime renderings that will be lit primarily through artificial lighting.

To use artificial lighting, place lighting fixture components in your building model. Then use the artificial lighting controls in the Rendering dialog box to specify the light settings used in each view.

Renderings that use artificial lights can take a long time to run (up to several hours, depending on your computer’s hardware and the rendering settings chosen) because the effects of the light produced by each fixture that is turned on must be calculated. When using artificial lights, choose your rendering settings very carefully:

  • Use draft renderings to get quick results and identify any problematic elements.
  • Limit the region rendered to focus on specific areas as you test the effect of lighting settings.
  • Turn off any lighting fixtures that are not needed to provide light for this view.
  • Adjust the exposure settings to control the overall brightness of the image and the highlights and shadows.
  • Reserve the higher-quality settings for final renderings, when you are confident about the expected results.