3ds Max and Revit Interoperability - Part 09 - Day Scene Lighting
In this tutorial, you experiment with a Daytime lighting scenario based on an exported Revit scene. You test out the default parameters and then learn to improve on them.
- Recorded in: 3ds Max 2015
- This tutorial is intended for use with 3ds Max version 2015 or higher.
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Now that you have two FBX files to test out, you'll start by experimenting with a day scene.
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In 3ds Max, reset your scene.
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Import and link the day scene you created earlier or you can use the provided file named room_day.fbx to that effect.
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Use the Combine by Family Type method as you have done before and attach the file.
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Because Revit always exports a Daylight System, you are prompted to use Exposure Control.
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This is needed to compensate for the brightness of the sun, much like with a real-world camera.
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The default Exposure Value is set to 15. It is a good starting point for daytime rendering.
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Click Yes to proceed; the scene gets loaded.
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Zoom out and take a look at your scene. Note the presence of the Exterior camera and that of the Daylight System.
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Click an empty point in the viewport to deselect all objects.
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If you look closely, you'll notice that the artificial lights inside the room are shown in black.
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This is actually an indication they are disabled.
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To make it easier to see inside, you can hide the curtain wall.
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This can be done by selecting its components in the viewport and then right-clicking and choosing Hide Selected.
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Another easy way is through the Scene Explorer.
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Sure enough, if you were to select any interior light and check its parameters in the Modify panel, you can see that it is Inactive.
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That's fine for a day scene.
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The Daylight System on the other hand is certainly active and is made of a direct light source or Sunlight simulating the sun,
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and a global source or Skylight simulating earth's atmosphere.
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Go to the Motion panel and notice that the time of day is set to 14:00 or 2pm as specified in Revit.
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If you were to make changes to the time of day or the North Direction, there is not much feedback in the viewport.
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This is because the viewport is set to Shaded mode by default in 3ds Max Design.
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You can click that label and switch the mode to Realistic.
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Still, not much change when you edit the Daylight's parameters.
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You may need to disable Adaptive Degradation depending on system performance.
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Click the Realistic label again and choose Lighting and Shadows > Illuminate with Scene Lights.
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The viewport shading is now affected by the lights in the scene.
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Now try to change the North Direction and see the feedback in the viewport.
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Settle for a 265-degree angle.
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Now press C to set the viewport to display the camera viewpoint.
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Do a test render. Not bad, but we can still tweak it a little bit.
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You can see the effect of direct sunlight and shadows.
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You can also see the effect of global lighting as it illuminates the surroundings and the inside of the room.
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This requires tweaking as well.
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Notice also the background, as it shows a sky with few clouds as specified in Revit.
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Let's see how we can make things better: First, let's do the same test render in higher resolution. This will make it easier to see detail.
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Click the Render Setup icon on the render window. It can also be accessed from the main toolbar.
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Set the Output Size to HDTV. This will result in a nice 16x9 aspect ratio.
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Choose a preset dimension or type in a value. For this movie, I'll use 960x540.
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Dismiss the dialog and test render again.
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In general, the rendering is still a bit dark. You'll need to adjust the Exposure Value a little bit.
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Click the Environment icon to access that dialog.
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Set the EV value to 14 and try again.
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This is better, overall the scene is brighter and we can make out the inside of the room.
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The clouds in the background are a little less visible though.
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The clouds and the background for that matter are part of a special map called mr Physical Sky.
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This usually gets defined when you create a Daylight System, including when you import it from Revit.
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So, in essence, a Daylight System is really made of three components: a Sun, a Skylight and a background in the form of the mr Physical Sky map.
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The reason I mention this is because the three work together.
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Typically all three should be enabled or disabled together for the scene to work well.
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More on that when we test the night render scenario.
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For now, to make the clouds more visible, open the Material Editor.
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Drag the mr Physical Sky map from the Environment dialog into the Material Editor as an instance.
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Double click the clouds map node and set the brightness slider to about 20.
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Test render the scene again. The clouds are now more visible.
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Do not go overboard with this slider, too high a value usually yields unexpected and unwanted results.
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As mentioned a second ago, the inside is still a little dark.
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If the building was meant to be viewed from the outside only, you would be fine with this setup.
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But if the building is meant to be open or transparent (so we can peek inside), then you need to do some extra work.
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There are many ways to improve the rendering solution:
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First, you can improve the quality of the rendering by increasing the Final Gather precision and the number of FG Bounces.
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Final Gather Precision increases the number of rays needed to calculate the solution,
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while FG Bounces defines the number of times these rays bounce off surfaces to add to the global illumination solution.
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Keep in mind that while this can give you some promising results, it can also increase rendering time exponentially.
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The same scene that took 15 seconds to render a moment ago,
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is now taking about 1m20s, and this is a very simple scene.
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Personally, I always try to look for ways to keep rendering time at a minimum, even if I have to rely on "non-physically accurate" methods.
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One of my favorite methods is to use a light source for Ambient Lighting only.
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Create an Omni light which is the same as a point light anywhere in the scene.
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Use the Move tool and the Transform Type-ins to relocate it to 0,0,0. This is essential for this method to work.
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In the Modify panel, go to Advanced Effects and ensure the light works in Ambient Only mode. That's all you need it for.
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Because an omni light is not physically accurate, you'll need to fiddle with its parameters.
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This is especially true when you use it in combination with a Daylight System and Exposure control.
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Currently, it doesn't havet much effect on the scene, if any.
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In the Modify panel, set the light's Multiplier value to about 3000. You can experiment with this if you want.
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Test render again. The inside is brighter but now appears a bit washed out.
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To bring more shadows where surfaces intersect, you'll use Ambient Occlusion.
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This is a process invented by ILM and often referred to as a "dirt map".
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In effect, it darkens areas where surfaces intersect, in this case mostly the walls and floors.
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With the light still selected, click the Projector Map button and set it to use an Ambient/Reflective Occlusion shader from the mental ray maps list.
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A test render at this time takes you back to the original look but that's only because you need to adjust the Ambient Occlusion shader.
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Drag the Ambient Occlusion map to the material editor as an instance.
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Double-click it to view its parameters: at this point, you're really only interested in the Max Distance value.
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You want to set a value here to tell 3ds Max how far to look for intersecting surfaces.
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A value of 0 looks to infinity and is not recommended.
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Set it to about 3 or 4 feet,
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and test render again.
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This is much better and still rendering in the 15-second range, so this method doesn't penalize rendering time much.
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You can also see how much nicer a rendering with AO is if compared to one without.
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Now that you've taken a look at a daytime scene and how to set it up, you will next look at defining a night scene.
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This is what you do in the next movie.