V-Ray Exposure Light Trails

V-Ray Exposure Light Trails

V-Ray Exposure Light Trails

My wife is a photographer, she was taking long exposure twilight shots one evening last week and produced some amazing results.  This had me rather interested in replicating the light trails in V-Ray, which in turn would be a great tool for architectural visuals.  Luckily I do cover photographic terms, camera settings and as such put a significant portion of workflows and tutorials in my new V-Ray book, V-Ray My Way.

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For this workflow I will be using 3D Studio Max and V-Ray of course.  We are also going to be using V-Ray Lights and V-Ray Physical Cameras.

Some of you may find this a waste of time, but I am not a believer in vast post-processing.  So in performing as much as possible within 3D Studio Max, you can retain the same levels of lighting wherever you place a camera.  Not everyone agrees with this, however it works for me 🙂

So with that in mind lets take a look at how we can achieve this lighting phenomenon.

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To begin with >

Clear your mind, refresh yourself and grab a coffee (or tea in my case), we are about to embark on a rather meaningful journey and read about topics that are often overlooked.  I will provide examples along the way of what the important settings do in V-Ray so you can come back and refer to them as design notes.

Firstly you can download the scene here, in a zipped file, you will need winrar!

Download Highway .MAX file

Download Experiment .MAX file

Download WinRAR

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Now we can begin

So now you have the files on your machine you should see the following in your Max World >

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A fairly simple scene set up specifically for obtaining the light trails.  In this scene you have the following:

  • Tea Pot Cars: Created to help link the moving head and tail lights to.
  • Highgway: Textured Surface with slight blurred reflection
  • Street Lights: Temperature controlled light mimicking orange street lights

Let us now perform a quick observation of how we have the Tea Pot Cars configured.

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The Tea Pots have been raised from the road surface, and yes they do not have wheels, but we will not be able to see them in the render anyway due to the long exposure photograph we are going to simulate.  Let us now take a quick look at the Frame 24 that we will be rendering.  Press ‘C’ on your keyboard.  Adjust your time slider and see the Tea Pot Cars move.

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The left view-port shows your camera view indicating what the scene looks like at Frame 0 on your time slider.  The camera view on the right shows the scene at Frame 24.

So you have three lanes of traffic moving towards and away from your camera.  This will give us nice enough light trails of the head lights and tail lights.  This is just a test, you can adjust, increase or decrease the amount of lights for your own scenes.

Now, let’s jump in to the theory behind the SLR camera and the settings we need to focus on.

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Long Exposures & V-Ray

When you use V-Ray Physical Cameras you will see that there are many settings to adjust and tweak to obtain your desired result.  These cameras work like real world digital SLR cameras.  You just need to learn how to manipulate them.  Long Exposure Photography is the art of using long duration shutter speeds to capture a still image yet yet process and obscure the moving elements in that picture.  So in our Render the camera will blend the moving light trails giving us an organic looking realistic effect.  The Shutter Speeds can be anything from 1 second to 45 minutes!

In 3D Studio Max we manipulate these settings, combined with light settings to achieve similar results.  It is essentially experimenting and finding the right selection for you!

I highly suggest taking a look at this long exposure guide, it gives you a great starting point for your camera settings: Long Exposure Guide

Test

This image was taken using V-Ray Physical Camera with motion blur enabled, from the Testing .Max scene you have downloaded.  Frame 5 of 25.

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Back to your 3D Studio Max Scene

I would like you to open the Experiment .MAX file, here you can use this file to play with the settings and learn more about what the settings do.

With the file open go to the camera view. (C on your keyboard)

Slide your time frame to 15 if it is not already in this position when you open the file.

Press F9 and create a Render, here is what you should have:

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Here you have a Tea Pot Car that has 2 x rear lights and 2 x front lights.  You can select each light and view its settings.  These lights are V-Ray Lights in the form of a plane.  They are set to visible as we want to pick them up in the long exposure shot.  I also add a VRay  Light Material to the mesh where the lights are, both front and rear.  Frame 22 is the shot you see here.  One important element is to make sure the Tea Pot does not render, so right click on it and from its properties un-check renderable.

Next

Select the camera and go to it’s properties.  Scroll down to the Sampling roll-out.  Change the subdivs to and enable Motion Blur.

Here is what you should have:

IV_S_6

Notice the light streaks are not very pronounced.  We will fix this later in more detail.  But for now we will alter the subdivs to 10.0.  Here is the result:

IV_S_10

The light streaks are beginning to become more apparent.  Let us continue to alter the subdivs.  Change them to 15 now.  Perform another render.

Here is the outcome:

IV_S_15

This is much better, so we can now turn up the subdivs to 24.

Here is the render output:

IV_S_24

Significantly better.  Again, it does take longer to render, but this is to let you experiment and develop your own way of working.  In the next section I will outline how to make longer trails and actually put it into a usable scene

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