Right-click and select Export Texture Image and save it in the same place as your Kerkythea scene.. To do this just make a copy of the texture image and open it in GIMP.. Then just load
Trang 1Chapter 8
[ 267 ]
3 Now go to the materials pallet and click the In Model tab.
4 Select the thumbnail that corresponds to the 2D tree
5 Right-click and select Export Texture Image and save it in the same place as your
Kerkythea scene
6 Now export your scene to Kerkythea as usual
7 In Kerkythea, right-click the tree material and select Edit Material.
8 This opens the material editor (see the following screenshot)
9 Click Diffuse.
10 Click the texture thumbnail under texture editor
11 Under Clip Mapping, right-click Texture.
Trang 2Photo-Realistic Rendering
[ 268 ]
12 Select the second icon (Add Bitmap).
13 Select Browse, and find the image you saved from SketchUp.
14 Click on the thumbnail in texture editor again
15 Then under Bitmap Options, tick Alpha Channel (This option will only appear when
you click the thumbnail)
16 The large thumbnail (bottom left) will now have changed to a black and white image showing the alpha channel (clip map)
17 Click Apply Changes.
18 Re-render
19 You should now have fixed the problem as you can see here:
Trang 3Chapter 8
[ 269 ]
What just happened?
2D trees and people are often created as PNG files with transparency The transparency
information is saved in the form of a channel, called the Alpha channel Normal images
have just three channels, red, green, and blue This is just an extra one All you've done here is to tell Kerkythea where to find that Alpha channel, and that you want it to be used
to clip the image If you want to you can create clip maps manually in GIMP for your
materials For example, to create holes in a fence
Have a go hero
Have a go at making a clip map To do this just make a copy of the texture image and open it
in GIMP Then create a new black layer and paint white on it wherever you want a hole to be Hide the original layer and save it as an image Then just load the black and white image into the Clip Map slot in Kerkythea
Creating bump map materials
Some materials need a bumpy surface to render accurately You can do this with wood grain, leather upholstery, and even water It's the same principle as clip maps, but this time the black and white image refers to how far the surface is raised Try these steps to see it in action
Time for action
1 In SketchUp draw a cube and apply a tile material to each face
2 Set up shadows and rotate the view so that the shadows are facing towards you
3 Go to View | Animation | Add Scene.
4 Export to Kerkythea
5 In Kerkythea go to Insert | Omnilight This places an omni-directional light
at the location of the camera (like a headlamp) to light the scene head on
6 Select the tile material and add a high amount specular in the material editor (say 65%) and set Shininess to 125
Trang 4Photo-Realistic Rendering
[ 270 ]
7 Perform a render using Raytracing Low, and you'll get an image like this one:
Notice that whilst the two sides look fine, the top surface with sunlight reflecting off it looks wrong because the specular highlight is uniform (see top right of the box) This is why for outdoor scenes, where very few materials have specularity, plain flat photo textures look fine without bump But when you have a shiny, bumpy floor indoors, we need some help!
8 In SketchUp go to the materials pallet and click In Model.
9 Right-click on the tile and select Export Texture Image.
10 Save it where you exported your Kerkythea scene
11 In GIMP, open the image you just saved
12 In the Layer pallet, select New Layer (bottom left).
13 Use the Magic Wand to select the tiles Change the Threshold if you need
to Finding the right value for this is a matter of trial and error until you
select the whole tile as you can see here:
Trang 5Chapter 8
[ 271 ]
14 Hold down Shift and select the other tiles too.
15 Select the Paintbucket tool from the main tool pallet.
16 Click the double arrow under the pallet to change the foreground color to white
17 Click on one of the tiles to fill the whole selection with white
18 Now go to Select | Invert.
19 Click the double arrow again to select black foreground color and use the
Paintbucket again in the selection.
20 Go to Select | All then Filters | Blur | Gaussian Blur to create a less sudden
gradient from black to white (a less harsh bump effect in Kerkythea)
21 Set Radius to 2 then hit OK.
22 Save the image as a JPG or PNG file You should have something like this:
23 In Kerkythea add the image to the Bump channel of the floor tile material just like you did for the clip map
24 Re-render using 02 Raytracing - High +AA and see the difference!
Trang 6Photo-Realistic Rendering
[ 272 ]
What just happened?
You just added a black and white image to the bump channel of the floor tile material.
This image tells Kerkythea that wherever there is black there should be depressions in the surface, and white should be raised Notice how this effect is only noticeable on the surface where highlights exist The omni light was used as a fill-in light for the sides of the box which were in shadow When you insert an omnilight it appears at the position you're viewing from
Pop Quiz
1 Which render setting is a good "one size fits all" setting for quick renders?
2 What does a depth render show?
3 Is it possible to import and update selected parts of a SketchUp model into a Kerkythea scene without changing the rest?
4 What's the best render preset for a sunlit scene?
5 What setting would you use if a scene has lots of lights and reflective surfaces?Summary
In this chapter, you've learned how to take the scene you've set up in SketchUp and give
it photo-realistic lighting This is as easy as exporting the file and clicking Start Render in
Kerkythea because SketchUp exports both Sky and Sun lighting information You learned
a time-saving method of using the right render presets in Kerkythea to preview and change materials and lighting You then learned how to tweak SketchUp materials in Kerkythea to add a little Specular and Reflection here and there
You also learned a few more advanced techniques which you can build on:
How to replace or edit SketchUp materials within Kerkythea
How to check and rectify common texturing import problems
How to set up and modify lights in SketchUp and import to Kerkythea
How to quickly check light levels in the scene with Clay Renders
The most effective render presets for various lighting setups
How to create bump materials in GIMP
How to assign Alpha maps for clip mapping
Trang 7Chapter 8
[ 273 ]
Now's the time to go away and experiment with your own renders to put these techniques into practice Why not make some great renders of your previous SketchUp projects so you can show them off and put them in a portfolio? Keep this book to hand and dip into it as and when you need it and don't forget the great help forums at www.kerkythea.net and
www.cgarchitect.com, where you'll be lent a hand
If you want to look into other rendering software, I've listed the ones most commonly used with SketchUp in Appendix A, Rendering Software, along with their main features based on this book's suggested workflow Many of these have offered discounts to readers;
details can be found at www.provelo.co.uk/renderoffers/
In the next chapter, you'll learn how to further enhance your render by post-processing with GIMP
Trang 9Important Compositing and After
Effects in GIMP
In Chapter 8, Photo-Realistic Rendering, you created a photo-real rendering
of your interior or exterior architectural model in Kerkythea That's a big
achievement! But whatever you do, don't stop there! There are some important things you need to do to your image before it's truly worthy of your portfolio
Your grandma might think it's lovely as it is, but Santiago Calatrava is not going
to employ you on the strength of unfinished work.
In this chapter, you're going to learn the tricks in GIMP which the pro 3D visualizers use They probably have Photoshop with all the bells and whistles attached, but we can do it just as well in GIMP You'll find out how GIMP can help you to:
Modify levels to give ultra-realistic lighting
Produce a vignette to draw the eye into your scene
Add bloom to give glow to highlights
Blur foreground or background to simulate camera depth of field
Add lighting effects in GIMP
Composite several images together to insert your model into real life scenes
It's a lot to cover, so let's get going You can use some of the scenes you've already created in earlier chapters
Trang 10Important Compositing and After Effects in GIMP
[ 276 ]
Part 1: Tweaks and lighting levels
Rendered output from Kerkythea is superb There's no doubt about it And that's because it's
a physically accurate light simulator When you click Start Render it fires light beams at the
scene and recaptures them in the camera So, it's really just a digital camera with simulated digital light What that means to you and me, apart from the superb results, is that light levels (saturation, white balance, and so on) aren't always right, straight out of the box And that's where GIMP comes in
Here's the piano scene you saw in the last chapter, which went on to become the front cover image Note the imperfections which detract from the realism:
Light shades are dull and washed out
No clear contrast between light and dark areas
Daylight quality is somehow unrealistic
Often when you've done a render you will not be entirely pleased with the result, and won't
know why This is usually down to something called Levels Let's have a go at adjusting levels
in GIMP so you can see what they are, and what are their results
Trang 11Chapter 9
[ 277 ]
Have a go hero – adjusting levels automatically
There are a lot of ways to fix the levels in a rendered image Some of them are easy, and these are the ones you should try first After that you'll look at the more involved way of doing it, which will usually yield better results
1 Open your render in GIMP
2 For a quick levels fix, first go to Colours | Auto | Equalize.
You can see five other Auto levels options on the menu If Equalize doesn't do it for your image, hit Edit | Undo and try some of the others on the menu:
White Balance: Corrects photos that have impure white or
black colors
Color Enhance: Colors should come out more vivid without
changing brightness
Normalize: Scans the image and stretches the brightness values
across the full spectrum to make the darkest black, and the lightest white
Trang 12Important Compositing and After Effects in GIMP
[ 278 ]
Stretch Contrast: Same as Normalize but does this for each color
channel independently, so you may find that colors change
Stretch HSV: Not usually used as the effects can be a bit random
3 Alternatively, if you have access to other image editing software that's designed for quick digital photo correction, try some of the auto-fix settings on those (for example, Photoshop Elements or Picasa) They tend to be very good and hassle free
4 The last, and possibly best, way of automatically tweaking levels is to open the
Levels dialogue and click the Auto button Do this by going to Colour | Levels.
What just happened?
You found the color settings in GIMP and tried out a few automatic levels tools to see what they did to your image A lot of these settings are to individual taste, but they're all there on the color menu for you to try out and see what you think Often they won't work because
the image has more than one problem Remember to make use of the Undo History on the Layers, Channels, Paths, Undo pallet, which can be accessed in the Windows menu,
as you experiment
Adjusting levels manually
You're now going to learn one of the most powerful and versatile image editing techniques available Once you get into this method you will not need any one-click presets and you'll be able to tweak light exactly how you want it This is worth learning as it will give your images that extra edge
Time for action – the levels dialogue
1. Once you have your image open in GIMP, go to Colors | Levels.
2. The levels dialogue box opens You should see something like this:
Download from Wow! eBook <www.wowebook.com>
Trang 13Important Compositing and After Effects in GIMP
[ 278 ]
Stretch Contrast: Same as Normalize but does this for each color
channel independently, so you may find that colors change
Stretch HSV: Not usually used as the effects can be a bit random
3 Alternatively, if you have access to other image editing software that's designed for quick digital photo correction, try some of the auto-fix settings on those (for example, Photoshop Elements or Picasa) They tend to be very good and hassle free
4 The last, and possibly best, way of automatically tweaking levels is to open the
Levels dialogue and click the Auto button Do this by going to Colour | Levels.
What just happened?
You found the color settings in GIMP and tried out a few automatic levels tools to see what they did to your image A lot of these settings are to individual taste, but they're all there on the color menu for you to try out and see what you think Often they won't work because
the image has more than one problem Remember to make use of the Undo History on the Layers, Channels, Paths, Undo pallet, which can be accessed in the Windows menu,
as you experiment
Adjusting levels manually
You're now going to learn one of the most powerful and versatile image editing techniques available Once you get into this method you will not need any one-click presets and you'll be able to tweak light exactly how you want it This is worth learning as it will give your images that extra edge
Time for action – the levels dialogue
1. Once you have your image open in GIMP, go to Colors | Levels.
2. The levels dialogue box opens You should see something like this:
Download from Wow! eBook <www.wowebook.com>
Trang 14Chapter 9
[ 279 ]
The graph, called a histogram, shows the light values in the image (or layer) from lightest (to the left) to darkest (on the right) So, as you can see from this histogram, all the detail in the image is happening in the middle of the graph The very light and very dark areas of the graph aren't being used at all This makes for a very washed out, low contrast image as you can see from part of the image here:
Trang 15Important Compositing and After Effects in GIMP
5. Click OK You will now have corrected the contrast in the image.
Can you see how much clearer this image is?
6. Go to the levels dialogue again and notice the change in the histogram
It might look a bit like this one:
Trang 16Chapter 9
[ 281 ]
What just happened?
You took the lighting level information contained in the image and stretched the most used part to fit over the entire light range Notice how the mountain range now fits the entire area? Each pixel in your image can now have a value of between 0 and 255, whereas before the image was confined to something like between 14 and 188 (see the first histogram) By dragging the white and black arrows you told GIMP to forget the flat areas before and after the mountain range, enhancing the contrast
Time for action – adjusting light quantity
1. While you're still in the levels dialogue, click on the middle arrow and drag it
to the left The image preview becomes lighter
2. Now drag it to the right The preview image becomes darker
3. Move it where you're happiest and click OK.
What just happened?
The middle arrow controls the Gamma value This tells GIMP whether to favor the left (light)
or right (dark) side of the histogram This is the correct way to brighten the image because none of the actual image information is lost If you close and open the levels dialogue again, you will see that the histogram has not changed in any way
Correcting individual color channels
Now comes the really good bit; I hope you're up for a challenge Did you know that most digital images are split up into red, green, and blue channels? Using levels you can edit each of these separately in exactly the same way as before This will allow you to balance the light levels out perfectly and get rid of unrealistic color tints, or even introduce some for your own purposes:
Red: Warmer lighting for interiors
Green: Increase this for leafy outdoor scenes, but it makes interiors look ill
Blue: Increase this for realistic natural light
Trang 17Important Compositing and After Effects in GIMP
[ 282 ]
Have a go hero
Notice above the histogram, is a box saying Channel: Value This means the histogram is
taking the combined value of all the red, green, and blue channels together If you click in that box you can select any of the three color channels to edit separately Do this now and edit the three arrows for each color separately Once you've done all three colors, go over
them again until you're happy with the result Then before you finish, go back to Value and
give the whole ensemble a final tweak
Removing unwanted image noise
Now let's look at the final render from Chapter 8 If you look carefully, or zoom in to a small area of the image, you can see a speckled effect
Trang 18Chapter 9
[ 283 ]
Grainy images like the one above are the hallmark of progressive render techniques such as
Metropolis Light Transport (MLT) or Path Tracing Progressive, which you will have used for
your final render in Chapter 8 It can add an appealing film grain effect a bit like the crackle
on an old vinyl record But too much crackle and we don't enjoy the performance If you master the noise removal technique you will be shown here, you will save bags of render time, because you don't need to wait for so many render passes
Time for action – find a way of removing noise
1. Take your final render and open it in GIMP
2. Duplicate the layer by clicking on the button at the bottom of the Layers pallet.
3. Select this duplicate layer
4. Use Filter | Blur | Gaussian Blur Try a small radius of say 2-4 pixels.
Trang 19Important Compositing and After Effects in GIMP
[ 284 ]
5. Use the Opacity slider (shown in the previous screenshot) to adjust the effect
of this layer on the original image beneath It's a trade-off between less noise and more detail
6. Here's the same area again with Gaussian Blur radius 3, and layer opacity set to 75%
7. Create a layer mask if you want to block out areas you don't wish to apply the effect to (go ahead and check back to Chapter 7 if you can't remember how to
do this, though it's not an essential step here)
8. When you're done, select the upper layer and go to Layers | Merge Down.
9. This makes the change permanent and puts everything back to
one layer ready for you to carry out other image edits
What just happened?
You created a slightly blurred copy of the image and overlaid it on the original You then adjusted the opacity of the blurred layer so that the effect of the layer would reduce or increase This way you can fine tune the effect Getting rid of noise is never perfect Either you will lose detail, or you will have a lot of detail but lots of noise Of course, the alternative
is to go back to Kerkythea and render for longer Finally, you can also try the Depth of Field
effect which you'll be covering in a few pages An additional benefit of this is also to reduce image noise
Trang 20Chapter 9
[ 285 ]
Do you notice it when you print?
When printing out your image, often the noise/grain doesn't show in the print So, give it a test print and see, you may be worrying about nothing!
Have a go hero
A more involved alternative to the quick fix you've just learned is to try downloading and
installing the G'MIC plugin for GIMP You can find it at http://gmic.sourceforge.net/gimp.shtml The dialog box within GIMP is shown here:
Trang 21Important Compositing and After Effects in GIMP
[ 286 ]
Here's the G'MIC version of our image after applying the PhotoComiX smoothing filter with
the settings shown in the previous screenshot
If you're up for it, download and install the plugin now using the instructions on the website Open your image in GIMP and try some of the filters and settings until you get a great result
If you have some money to spend, Neat Image by ABSoft is hard to beat, with exceptional quality output, speed, and ease of use You can get a free trail of this software at http://www.neatimage.com
Light bloom
On bright days the sun puts a halo of light round objects in direct sunlight You can achieve this effect easily in GIMP This is a good way to soften an image, making it more dreamlike
Time for action
To add some soft glow to the edge of lights, take your final render and just follow these steps Let's start with this small area of the final render: