Essential Blender- P26 pps

Notice that the bottom set of Layer buttons for the "1 Render Layer" layer only includes objects from scene Layers 1 and 11.. Looking at the node network, a new Render Layer node has bee

Figure RCD.33: Render Layer settings for the foreground

Figure RCD.34: Render Layer settings for the background

Notice that the bottom set of Layer buttons for the "1 Render Layer" layer only includes objects from scene Layers 1 and 11 The Layer buttons for the "Background" layer include objects from scene Layer 2

Looking at the node network, a new Render Layer node has been created with

Add->Input->Render Layers, and set to use the "Background" render layer at the bottom of the panel As you will only be darkening and blurring this layer, you can stick with the default "Combined" pass

Figure RCD.35: The "Background" Render Layer node

Immediately after the "Background" Render Layer, we have added an RGB Curves node to

darken and reduce the contrast of the render Contrast can be reduced by performing the opposite

of the "S Curve" — darkening the light areas and brightening the shadows

Before putting both layers together, though, you can use an old trick to help bring out the

foreground objects

Quick and Dirty Depth of Field

A simple blur applied to the background makes it look as though the camera lens is focused on the gauge

Figure RCD.36: The Blur node for the background

A Gaussian blur has been applied with X and Y settings of 5 We have used the Gamma button to emphasize the bright parts of the image, ensuring that the out-of-focus dials remain visible Also,

as we're pretending that the background is blurred due to camera focus, it might be worth it to use the Bokeh option

Figure RCD.37: The blurred, darkened background layer

The combination of the steam gauge with the background can be accomplished, once again, with the Mix node This time, however, you will use the default Mix mode How can you get the node

to not blend the entire area of the images together, though? As you've already learned, adjusting the Factor affects how much of the image from the lower input socket is composited over the other In addition to just being a number, though, the Factor setting can also use an image as its input

By connecting the Alpha pass from the original Render Layers node, portions of the image that were completely opaque (the gauge itself) receive a Factor setting of 1.0, while the non-rendered areas receive a Factor of 0.0 The result is that the Alpha pass is used as a mask for the Mix node

Figure RCD.37.1: The Alpha Channel from Render Layer 1

Figure RCD.38: Mixing the background with the rendered element

Figure RCD.39: The rendered, composited image with background

Before you finish, you'll look at one more excellent use of the Compositor, one that's suited to animation but that can also enhance single-frame renders

Vector-Based Motion Blur

Load the file "CompositeStage7.blend" and render to fill the passes

Figure RCD.40: The node network for compositing the spinning pointer

With this file, you will produce the animation However, as the only thing that moves is the

pointer on the gauge's face, it would be a waste of time to render the entire image once for each frame The animation for this piece is 250 frames long, and each frame takes, on the computer used for this discussion, almost a minute to render That is almost four hours of render time If you use a single minute-long render to produce a background, then render only the pointer as it spins, you can reduce the per-frame render time to around two seconds, saving nearly three hours and fifty minutes of render time!

In this new file, you will see that only three objects exist: the pointer and the main body and face

of the gauge You will only use the render of the pointer when you make the final composite, but the shape of the gauge itself will be useful too

When producing an effect like this, you will need to have already rendered the rest of the image, without the animated portions, to use as a background We have already done that in the example file, bringing the image into the Compositor with an Image node found in Add->Input->Image Also, the only 3D objects left in the file are the pointer itself, the main gauge body and face, and the lamps If you had wanted, you could have simply moved the extra objects to a disabled layer

Blender has two methods of producing motion Blur The older method, available with the

"MBLUR" toggle in the Render buttons, relied on rendering an entire scene several times on fractional frame numbers, then combining the results Of course, this came at the cost of having

to render your whole scene up to sixteen times per frame Vector-based Motion Blur, on the other hand, uses the Compositor to examine how the objects in a scene are moving, then builds a new image with moving objects smeared along their trajectories and blended into the scene

Figure RCD.41: The Vector Blur node

Vector Blur is found under Add->Filter->Vector Blur To make it work, you will need to have some sort of image to blur (either a Combined pass or a composited image), and the Z and Vec passes enabled in the Render Layers tab of the Render buttons In this example, all three input sockets connect directly to their output counterparts on the "1 Render Layer" node

Figure RCD.42: The pointer blurred on Frame 189, before compositing

Obviously, objects will need to be in motion on the rendered frame for Vector Blur to have any effect

Note: As you need a good Alpha channel with which to composite, remember to switch the

Renderer from Sky to Key mode on the Render tab

Figure RCD.43: Key mode on the Render tab

Completing the Shot

To finish this example, the dial needs to be mixed back over the background image

Figure RCD.44: The Alpha Over node

When compositing an image with built-in Alpha (a render of a lone object like the pointer), the AlphaOver node does the job AlphaOver is found in Add->Color->Alpha Over It follows the same socket stacking rules as the other nodes, with the base image in the upper socket and the image with Alpha in the lower socket

In the example, the saved image of the gauge is used as a backdrop in the top Image input, while the vector-blurred pointer with built-in Alpha fills the bottom Image input You can see from the final composite, though, that something is wrong

Figure RCD.45: Composite with the pointer sticking out

One last trick, then, to properly mask the pointer This is why you still have the gauge body and face hanging around

In this file, both the gauge body and face have been placed on Layer 2, and a separate Render Layer created for them called "Gauge Body." With the body itself selected, it has been assigned

an Object Index by using the "PassIndex" spinner on the Objects and Links panel of the Object buttons (F7)

Figure RCD.46: The PassIndex of the body set to 1

In the Render Layer settings for the "Gauge Body" layer, you can see that all passes have been disabled with the exception of the IndexOb pass You don't need to care about colors, materials or shading here: you want a pass that will generate a mask of this object to use on the pointer The PassIndex value of all objects defaults to 0 unless changed by you By assigning a PassIndex of 1

to the gauge body in the Object buttons, you will be able to single it out in the Compositor

Figure RCD.47: The node network to build a mask from an Object Index pass

The IndexOb pass from the Gauge Body Render Layer (note how with no Combined pass sent, there is no image at all in the preview) is connected to an ID Mask node, from Add->Converter-

>ID Mask

The ID value in the ID Mask node is set to 1, to correspond with the value you set on the 3D object After that, an RGB Curves node is used to invert the resulting mask That image fills in the Factor input socket on the AlphaOver node, correctly masking the spinning pointer and

completing your shot

Figure RCD.48: The final shot, correctly composited with the animated blurred spinner

Getting the Shot Out of Your Department

So, you’ve finally finished the job The managers who have been planning the production had allocated five hours to your department on this shot for rendering and sweetening Because

you’re a pro with the Compositor, you were able to set up the nodes in only a half hour (perfectly reasonable once you’re experienced), and rendered the finished animation frames before the rest

of the first hour was up

Have a sandwich Grab some coffee You’ve earned it

Well, the Compositor’s earned it, but you can take the credit

Chapter 13: Render Settings: Discussion

By Roland Hess

There are only a few useful settings for the renderer that are not related to compositing

RSD.01: The Render Buttons

The Render buttons are accessible from any buttons window, and can be found by clicking on the Scene context and Render sub-context on the header, or by pressing F10

When rendering, there are several things you need to specify: the render size, where and in what format to save the finished product, and the quality options you would like the renderer to use

Render Size

The finished size of the render is chosen in the Format panel, with the SizeX and SizeY controls The column of buttons to the right contains preset values for different rendering tasks

RSD.02: Setting render size and preset buttons on the Format panel

Output Format

Rendered images are not automatically saved You must press F3 to save them, or select "Save Image " from the File menu When Blender saves the image, it uses the format specified on the Formats panel

RSD.03: The different image formats available for saving

The default image format is Jpeg, but, as Jpeg compression can leave ugly artifacts, you should probably change it to PNG, and set the Quality spinner to 100 With this menu, you can also choose from the animation formats appropriate to your computer (Quicktime, AVI codec), which will bring up your operating system's animation saving dialogue

If you want to save an image's Alpha channel along with the rest of the render, you need to select the "RGBA" button at the bottom of the panel, as well as an image format that supports Alpha channels (Targa, PNG, OpenEXR and MultiLayer)

If you are rendering an animation and have chosen a still image format (PNG, Targa, Jpeg, etc.) instead of an animation format (.avi, Quicktime), Blender will save a series of numbered image files, one for each rendered frame It is then up to you to put the images together into a playable animation, using either Blender or some other program

Animated image sequences are saved automatically to the folder specified in the top file selector

of the Output tab

RSD.04: Animation file path selector on the Output tab

Oversampling

The render is basically a system that looks at the 3D scene for every pixel of the final image and asks "What color should this be?" In the simplest case, it just takes the object nearest to the camera on that pixel, figures out the location on the object that the pixel covers, and calculates the final color based on lamps, shadowing and the object's material What should it do, though, if one of the pixels in the final image happens to show the edge of an object? Should the renderer use the color and shading for the closest object, or the one showing from behind it?

This is the problem that anti-aliasing tackles If the renderer only chose the foremost object, final renders would look like this:

Figure RSD.05: Jagged edges anywhere one object ends and another begins

However, the renderer could actually pretend that that single pixel is made up of, say, four

smaller pixels Then, it could calculate a color for each of those, giving a more accurate picture of what's really going on at that object's edge After those four values are calculated, the results could be averaged, giving the final color for the image's pixel This process is called

oversampling, which is one method of anti-aliasing For images to look natural, it must be

enabled

Figure RSD.06: The same scene, with anti-aliasing

Anti-aliasing is enabled with the "OSA" button, which stands for "oversampling." Different levels of OSA can be set: 5, 8, 11 and 16 Lower levels give a less nice, though often acceptable, result The higher levels will take longer to render, but give smoother edges Always start at the bottom and only raise the level if the edges of your objects still show the kind of "stair stepping" visible in the first sample image

Figure RSD.07: The Oversampling buttons

Rendering Controls

The large Render button on the Render panel triggers a render That's kind of obvious, but it must

be said A render may also be triggered from any window type or screen within Blender by

pressing F12

If you will be rendering an animation, the large Animation button on the Anim panel does the trick Blender will render all the frames in the range between (and including) the Sta (Start) and End values at the bottom of the panel

At any time during either a single frame or animation render, the rendering process may be

stopped by pressing the Esc-key

Figure RSD.12: The Render and Animation render buttons

Technical Details

If you have a computer with a dual core processor (or more), you can have the renderer take advantage of it The "Threads" spinner on the Output tab tells Blender how many different render processes to run at once Dual core processors will be able to efficiently run two threads at once, while quads or two duals could run four at once

Note: If your computer has an Intel Core Duo or Athlon X2 processor, you can set Threads to 2

If you have a different multi-processing architecture than those two, you probably don't need us

to tell you what you have

Figure RSD.08: The Threads spinner set to 2 for use with a Mac Dual G5 computer

Speeding Up Test Renders

You don't always want to wait for a full quality render Sometimes, it's good enough just to see how a moved lamp or tweaked material looks in place with the rest of your scene

If you don't want to use the Shift-P Preview Render panel in one of the 3D views, your only option is to actually trigger a full render There are several ways to speed it up, if you are willing

to compromise certain aspects of the result

! Disable OSA: Turning off OSA will give a drastic speedup, as each pixel in the image will only go through a single round of calculations

! Disable Shadow: Disabling the Shadow button on the Render panel tells the renderer to entirely skip shadow generation and mapping If there are several lamps that cast

shadows, this will give the render a nice speed boost This button disables both buffered and raytraced shadows (see Chapter 11)

! Disable Ray: Disabling the Ray button on the Render panel skips all raytracing

calculations, including ray shadows, transparency and reflection For test renders that