Simulating depth of field Google SketchUp Visualization

Simulating depth of field

Thu, 28 Jul 2011 03:59:37 | Google SketchUp

This is a technique you'll use all the time. It adds a photographic realism to your image like nothing else can. Depth of Field is an effect created by the aperture settings in your camera. If you have a digital "point and shoot" you probably won't even be aware of it. It basically means that what you're focused on is sharp, while the foreground and background are blurred. The reason you might want to see this effect in your renders is because that's the way we see things through our own eyes. Most things are blurred apart from what we're focusing on, therefore the focus is a way of drawing attention to a particular area or element. So, let's give it a go. The following three images illustrate this concept:

First the render itself. Notice all of it is in focus; you can see the brick pattern clearly on each box.

Here's the depth render. You learned how to produce this in the previous chapter.

And here's the final image after the effect was applied in GIMP. You can tell the focus is on the box in the foreground, because the other two boxes are progressively more blurred.

Time for action - depth of field using a depth render

You will have output a depth render from the previous chapter. It should look something like this one here. Shades of black are closer to the camera, and whiter shades furthest away.

1. Open your main image in GIMP.

3. Select the depth render image and click OK. You should now have your render as the background layer, and the depth map on top.

4. Click on the Foreground square in the main tool pallet. You are taken to the Change Foreground Color dialog box.

5. Click on the eyedroper tool (circled in the following screenshot).

: I_11_11_11_11_11_I

Reset		OK	Cancel
		J

6. Make sure the depth render layer is selected, and now move the eye dropper tool over the image.

7. Hold down the left mouse button and watch the V value change (circled in the previous screenshot). It moves between 0 and 100 as you move it around over the depth map, depending on the grayscale value.

8. The values you are reading are a percentage of how far away something is from the camera. Note down the value you get when you pass over the area that you want to be in focus.

9. That's all you need from this dialogue. Click Cancel.

10. Download the Focus Blur plugin for GIMP from www.registry.gimp.org focus blur binaries the focusblur.exe file into the GIMP plugins folder (usually Program Files\gimp-2.0\lib\gimp\2.0\plugins).

11. Save your progress and restart GIMP and you will be able to access the new plugin.

12. Turn off the depth map layer (use the eye icon) so that you can see the main image.

13. Select the main image layer so that the following Blur filter works on that layer.

14. Access the plugin by going to Filters | Blur | Focus Blur.

15. Select Gaussian, change the Radius setting to control amount of blur required (according to your preference).

16. You can see the effect in the preview image. Move around with the sliders to see more of the image.

17. Select Use Depth map and select the depth render layer in the list box.

18. In the Focal Depth box, input the value you noted previously.

19. And that's it! Click OK to apply the effect.

Focus Blur

1 *

[71 Preview

Basic | Model || Shine || Depth || Preferences Diffusion Model and Radius:

n Gaussian	V
Peak radius for Shining:	0,00
H Use Depth map:
MO passes MLT gam..._ó Depth Map.png-5 v

Focal depth:

J 93.75

Focal depth:

J 93.75

Heip

Cancel

20. You can do this for any percentage value (1 to 100) to blur different areas of the image.

21. You can see in my image that the balustrade has been blurred and the stair remains sharp.

Apply some blur to the depth map image first. Sometimes this gives a better effect. The Kerkythea depth render isn't perfectly accurate at sharp corners and valleys, so applying a little blur can smooth this error out.

Lighting effects

What about some of the light effects you can add at the post processing stage? Let's not leave those out. Some exceptional artists can render a scene with just plain ambient light and then add all the other lighting using image editing software afterwards. So, while you probably don't need to do that, you might want to know how to do it as part of your toolbox. For example, you might wish to put some shining dots where the ceiling light bulbs would be. This technique is often applied with night scenes and street lighting.

Time for action - adding light effects in GIMP

Open your artificially lit render from Chapter 8.

1. Go to Filters | Light and Shadow | Supernova.

2. Click the zoom icon to zoom closer in the preview image.

3. Click where you want the centre of the light to be.

4. Adjust Color, Radius, and Spokes as necessary (refer to the following screenshot).

5. The values for Radius and Spokes I've used are 5 and 100 respectively, for the light you can see on the right of the preview image, but have reduced the values for the current light because it's at a shallower angle to the camera.

6. Repeat for each light bulb.

Here's the image with these Supernovas applied:

Have a go hero - discovering weird and wonderful lighting filters

GIMP has some great, some not so great, and some plain "far out" lighting effects that you've just got to sample for yourself to believe. They can be found under Filters | Light and Shadow. Try some of these out on your image and see what effects you can get. You might find some that are so good that you can leave out some lights in SketchUp or Kerkythea and add them in quicker GIMP on your next project.

Pop quiz

Now it's time for a quiz because I need to check whether you've really been listening; not daydreaming about the new chicken double mayo with mung-bean and sprout salad bap at Burger King. You'll have plenty of time to get your chops round that little beauty after your homework! But for now, clear your mind of temporal bliss and concentrate... Ready?

1. What are the options within GIMP for reducing noise in rendered images?

2. What color are the separate channels in an RGB image?

3. What do you do to the levels histogram to increase contrast?

4. Where do you get the figure between 1 and 100 to put into the depth of field box in the Focus Blur dialog?

Using a vignette layer to finish the image

When you're happy with your image, all that's left to do is further draw the viewer's eye into the image. This final process is the Vignette, which is a posh word for a dark border.

You've already learned all the skills you need for this in Chapter 7, Non-Photo Real with Sketchup. It was slightly different in that case because you used a white border to let the image fade out at the edges. With photo-real images you'll darken the edges slightly instead.

Time for action - fade out the edges with a vignette

To draw the eye to the areas of the image you wish to focus on, parts of it need to be lit more than others. The edges especially should be darker. The following screenshot is an exaggerated image showing where the vignette could go on this particular image:

1. In GIMP, create a new layer. For Layer Fill Type select Transparency. This is your vignette layer.

2. Select the Paintbrush tool.

3. Click on Foreground & background colors (shown circled in the screenshot) to get colors back to black and white.

4. Select a fuzzy circle brush and increase the scale to get a bigger brush.

5. Start round the edges of the image and apply black paint all round.

6. Change the brush Opacity to 50 and gradually come in from the edge where you want slightly more light.

7. Repeat with the setting still at 50 to overlay your paintbrush strokes, as you can see from the exaggerated image.

8. You can use a 20 opacity brush for fine tuning if you need to.

9. Remember, work fast because you can change this at any time. Simply click the eraser and paint over the areas you need to alter. Set the Eraser Tool at 50 if you need a less definite effect.

10. As you've done this really roughly, do a Gaussian Blur on the vignette layer at a high radius value (20 - 100 pixels) to smooth things out a little.

11. Now lower the Layer Opacity until you have just a subtle effect (I've used 30).

What just happened?

You added a final flourish to help draw the viewer's eye into the picture. This was achieved with a simple darkened overlay. Using this process you can emphasize or minimize certain areas of the composition. Here are the two images for comparison:

That's the end of this section of the chapter related to image enhancements. You have learned how to give your image that extra pizzazz that makes all the difference!

Average user rating: 5 stars out of 1 votes

TIEBIAOJI SketchUp Tutorials

» Google SketchUp Visualization