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Using two-point perspective correction

From: SketchUp Rendering Using Twilight

Video: Using two-point perspective correction

Oftentimes when producing visualization renders, a SketchUp artist will be asked to mimic the use of a perspective control or shift lens as employed by many visualization photographers. The basic idea of such lenses is that they give photographers the ability to control the appearance of perspective in an image. The lens can actually be moved parallel to the camera's sensor. Architectural photographers often make use of this functionality to avoid convergence of vertical lines in tall buildings, but of course it can be used to straighten the verticals in any perspective photograph.

Using two-point perspective correction

Oftentimes when producing visualization renders, a SketchUp artist will be asked to mimic the use of a perspective control or shift lens as employed by many visualization photographers. The basic idea of such lenses is that they give photographers the ability to control the appearance of perspective in an image. The lens can actually be moved parallel to the camera's sensor. Architectural photographers often make use of this functionality to avoid convergence of vertical lines in tall buildings, but of course it can be used to straighten the verticals in any perspective photograph.

Indeed, if we take a render of our start scene, you'll see why this kind of functionality--the ability to correct perspective--may also be something that we need to do inside of our visualization renders. Clearly, we have a number of vertical lines that are, well, not really vertical. They're leaning quite badly in fact. Now if you're a regular SketchUp user, then you're probably thinking, well, this is not a problem; SketchUp has perspective correction tools built in. One thing we do need to keep in mind is that those tools don't always work with third-party render engines; happily this isn't the case with Twilight.

To demonstrate how these tools work, I'm just going to dismiss our Twilight Render dialog and come up to the Camera menu, and we're going to come down and all we need to do is enable these Two- Point Perspective option. And as you can see in the SketchUp viewport, our leaning verticals are now standing nice and upright. Of course, our composition is a little bit off now, so let's just frame things up a little more nicely. Now of course, we want to go and take a test render. We want to be certain that Twilight has captured that perspective correction for us, which, as you can see, it most definitely has, although there does appear to be a little bit of a problem. We don't have the composition in our Twilight Render that we're seeing inside of our SketchUp viewport.

This really is a limitation of SketchUp's Two-Point Perspective tool. Once we have enabled it, we cannot perform any further viewport operations. Well, we can perform the viewport operations, as you saw us demonstrate, but our render engine will not capture them. The render we get will essentially be from the point at which our perspective correction was applied. If we do need to improve our composition a little bit, then we have to make certain that any alterations are applied before we use our perspective correction. Of course, this means a little bit of trial and error when it comes to setting up our cameras, but with a bit of work we can get both our upright vertical lines and our pleasing composition in the final render.

Of course, we could perform these perspective corrections in an image editing application such as Photoshop, but seeing as we have such an easy-to-use and readily accessible control in SketchUp, one that Twilight can render, it seems to make sense to apply this kind of perspective correction at render time.

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SketchUp Rendering Using Twilight

33 video lessons · 4339 viewers

Brian Bradley
Author

 
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  1. 4m 1s
    1. Welcome
      1m 5s
    2. What you should know
      2m 10s
    3. Using the exercise files
      46s
  2. 6m 53s
    1. Installing the Twilight renderer
      2m 52s
    2. Locating Twilight tools and features
      4m 1s
  3. 50m 22s
    1. Adding the Physical Sun and Sky
      6m 17s
    2. Employing the Point light type
      6m 35s
    3. Using the Spot and Projector light types
      7m 7s
    4. Adding the IES light type
      3m 48s
    5. Using light-emitting materials
      6m 59s
    6. Creating image-based lighting using High Dynamic Range Images (HDRIs)
      6m 12s
    7. Using Sky Portals for interior global illumination (GI)
      6m 43s
    8. Understanding the importance of reflectance in materials
      6m 41s
  4. 21m 54s
    1. Exploring Light Transport options in Twilight
      9m 18s
    2. Managing the Quality presets
      5m 57s
    3. Editing and saving presets
      6m 39s
  5. 22m 8s
    1. Positioning your scene view
      3m 23s
    2. Altering projection types
      5m 12s
    3. Working with depth of field
      3m 59s
    4. Working with focal length
      2m 44s
    5. Harnessing tone mapping, exposure, and gamma
      3m 59s
    6. Using two-point perspective correction
      2m 51s
  6. 38m 13s
    1. Introduction to Twilight materials
      8m 23s
    2. Creating diffuse surfaces
      6m 53s
    3. Creating reflective surfaces
      6m 53s
    4. Creating glassy refractive surfaces
      9m 28s
    5. Creating watery refractive surfaces
      6m 36s
  7. 31m 28s
    1. Rendering for animation
      8m 55s
    2. Rendering out an alpha mask
      3m 44s
    3. Setting up a depth render
      4m 3s
    4. Creating an RGB mask using the Diffuse Texture Pass preset
      5m 45s
    5. Working with a composite
      9m 1s
  8. 1m 13s
    1. What's next?
      1m 13s

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