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    QUIZ

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    Simple Rules for Lighting a Scene

    continued

    Photometric lights use real-world parameters such as lumens, candela, lux, and foot-candles to represent the intensity of the light, and they always follow the laws of physics for the natural decay of light over distance — namely, the inverse-square law.

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    There are certainly times where a standard light comes in handy — for instance, if you need to evenly illuminate a surface and do not want the inverse-square effect of decay or want a directional substitute for ambient light.

    In these instances, you probably understand the results you are trying to achieve and the pitfalls of working with standard lights. As a general practice, however, you should avoid standard lights and not use the None option for decay.


    Troubleshooting Problem Lighting

    When I am confronted with a scene that has lighting issues, it is usually because the artist began lighting their scenes by immediately adding lights everywhere they were indicated in the plan and then tried to make various adjustments to all the lights at once.

    Or, when faced with unsatisfactory results, they just kept adding lights in an attempt to improve the unacceptable render. The additional lights just made it more difficult to control scene illumination. The first thing I do is return to darkness — turn all the lights off but one — and work in isolation. If there is still illumination with all lights off, then I ensure that XRef scenes and containers are not bringing in unwanted illumination.

    With the use of photometric lights for architectural scenes, adding many lights at once is perhaps not as disastrous as it once was, because you are now working with physical values for the lighting intensity. This is the case with imported Revit scenes, where all lights are photometric and set to values related to the fixture specified.

    However, with all lights in place, you still deal with long renders, and it will make it harder to see the effect of changes to individual settings.


    Related to this rule is a tip to use a Light Meter helper object to determine the brightness of surfaces in your scene. With the Pseudo Color exposure control, you have already seen one method for determining lighting levels on all your surfaces. In a similar way, placing Light Meter objects at floor or tabletop level gives brightness values that can be used to determine whether you have acceptable light levels.

    Each arrow on a light meter shows a sampled lux value. You can create light meters by selecting Lighting Analysis > Create > Light Meter. With the Light Meter objects, you can work backward from desired floor light levels to then adjust your light's intensity values.

    Use Shadows

    Shadows create depth in your scene, add contrast to set objects apart and define edges, help to connect your objects to their surroundings, and define relative scale. Without shadows, you cannot tell whether something is tiny and floating right in front of the camera or is large and far away. In the Defaults And UI Switcher dialog box, there are four default options — two options for 3ds Max and two for DesignVIZ.

    The two options for 3ds Max have all newly created lights with shadows disabled by default, and as it says in the dialog box, this is done for placing highlights and adding fill lights. This need for shadowless lights is certainly a potential requirement in the DesignVIZ field, too; however, most lights should have shadows enabled.

    Use Hardware Viewport Shading to Preview Lighting

    One of the best ways to previsualize your lights and shadows is to use the viewport Hardware Shading mode available in Max 2010 and newer. The use of a high-performance workstation-class video card such as the NVIDIA Quadro series combined with Hardware Shading mode can simplify and greatly speed the process of lighting your scene.

    Because hardware shading in mental ray works with your exposure control, it gives you real-time feedback of lighting adjustments that closely match the direct lighting of your final rendering.

    Hardware-shaded viewport performance for orbiting and moving in a large scene might be an issue for you, depending on your video hardware and scene, and does not replace nonhardware legacy smooth or hidden-line shading for fast interaction with your scene.

    This technology is seeing rapid development at both Autodesk and mental images; mental ray 3.8 now supports the iray interactive lighting technology with global illumination (perfect for design visualization), and 3ds Max 2011 continues to improve the features and speed of hardware shading, particularly with mental ray materials.

    To enable hardware shading, press Shift+F3 or click the third viewport configuration button in your view, and then choose the Lighting And Shadows menu option. Select Illuminate With Scene Lights, Enable Exposure Control In Viewport, and Enable Shadows.

    Discuss this article in the Architecture Forum...

    Jennifer O'Connor is a visual design artist, instructor, speaker, and expert on mental ray and 3ds Max. She is the founder and president of 4D Artists Inc., a 3D rendering and animation company, and is an adjunct professor of 3D rendering, animation, and architectural illustration at the College of Lake County, Illinois. O'Connor has been working with CAD software since 1985 and 3D software since 1992, on projects ranging from museum animations and tropical islands to product visualization. Her blog mental ray for Design Visualization discusses the latest technology.

    This article is excerpted from Mastering mental ray: Rendering Techniques for 3D and CAD Professionals by Jennifer O'Connor, copyright ©  2010, with permission of the publisher, Sybex, an imprint of John Wiley & Sons.

     

    AW

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    SUBSCRIPTION SAMPLE

    These two renderings of the same scene show the results of two shadow types in mental ray: point shadows (left) and area shadows (right).
    Image: Courtesy Sybex

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    SUBSCRIPTION SAMPLE

    Mental ray supports a light metering mode capable of measuring total illumination at various points in a rendering, displaying the results as a false-color map.
    Image: Courtesy Sybex

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    The mental ray Light Lister dialog box.
    Image: Courtesy Sybex

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    The mental ray light template dropdown menu.
    Image: Courtesy Sybex

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    A bathroom scene rendered with photometric lights and daylight system. The exposure value is set at 7.0, which is low for an interior daylit scene.
    Image: Courtesy Sybex

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    The same bathroom scene with the Medium FG preset and two bounces. This mottled appearance is typical in interior scenes that have an exterior daylight component.
    Image: Courtesy Sybex

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    The final bathroom scene with the Medium FG preset, four diffuse bounces, and the Noise Filtering set to High.
    Image: Courtesy Sybex

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    Mastering mental ray: Rendering Techniques for 3D and CAD Professionals by Jennifer O'Connor.
    Image: Sybex

     

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