Essential Blender- P25 ppsx

It is possible to set up different Render Layers, each with their own node input, pulling elements from various modeling layers and scenes which can then be dealt with separately in the

Figure RCD.02: The node network for this composite

The Composite Node network for this exercise appears to be staggeringly complex However, it can be broken down into four distinct portions, each one covered here in depth There are a

number of files that will help with this chapter, all found in the "examples" folder on the included

CD The first exercise will require you to create the node network from scratch, but later ones will use pre-made files for you to examine and play with

Let’s start with the file as delivered to you from the production department Load

“CompositeStage1.blend” and perform a test render (F12) If you find that the render takes longer than a couple of minutes, you may want to consider working with the renderer set to 50% size in the Render buttons

Figure RCD.03: The file as provided

If you examine the scene, you will see that some of the materials use raytracing A simple

textured plane outside of the camera's view provides something for the dial's face to reflect

Creating the Source Renders, Scenes and Components to Composite

Change the wide window at the top of the screen from a 3D view to a Node Editor Switch to Composite Nodes with the face icon on the header, and make sure the Use Nodes button is

enabled

The window on the left side of the screen shows the Render buttons Both windows at the bottom have been set to UV/Image Editors for showing Preview and Composite result nodes You'll be focusing on the main gauge for the majority of this discussion, so disable Layers 2 and 11 to hide the background and wall elements

Figure RCD.03.a: Shift-LMB click on these two layer buttons

Figure RCD.04: A good setup to begin compositing

When turning on Use Nodes for the first time, the default is to have a Render Layers node

connected directly to a Composite node However, you are not limited to a single render input It

is possible to set up different Render Layers, each with their own node input, pulling elements from various modeling layers and scenes which can then be dealt with separately in the

Compositor

These controls are found in the Render Layers tab of the Render buttons, nested into the same panel as the Output tab

Figure RCD.05: The Render Layers tab

Render Layers

From this tab it is possible to control exactly what will be rendered, as well as what will be

passed to the compositor for processing In short, a Render Layer is a selection of scene layers that will be rendered in a single pass: a set of Layers that will be rendered together Each Render Layer can have its own Input node, allowing you to perform different composite operations on different sets of objects from your scene, as you'll see later

Let's look at the controls on the Render Layers tab:

Scene

Figure RCD.05.1: Scene layer buttons

This refers to the set of layer buttons at the top of the panel These controls are a duplicate of the layer buttons found on the 3D view headers, and are included here as a convenience As you will

be indicating which layers should be included with which render input in this same tab, it is nice

to be able to check the contents of layers without leaving the panel

Below this is the name and selector for the active Render Layer Like other name popups, new Render Layers may be created by selecting Add New and may be removed by clicking the "X" to the right of the control

Layer

Figure RCD.05.2: Layer Layer buttons

Further down is the Layer control, which again shows the familiar layer selector Unlike the one above, which controls what displays in the 3D view, this selector is the one that determines which scene layers will be included in this Render Layer When a Render Layer is created, it defaults to including all scene layers

Why would you need separate access to so many scenes and layers? You could, for example, divide a scene between background and foreground objects, sending the background objects to the compositor in a different Render Layer for blurring It’s also possible to have part of your project in a completely different Scene, allowing you to composite objects with completely

different render settings

Figure RCD.03: Figure RCD.06: A render composited from two scenes The ocean scene used standard render settings, while the mine and buoy scene used the Edge settings

Render Process

Image:Dummy.png

RCD.05.3: Render process buttons

Below the Render Layer selector are toggles for which portions of the renderer to use Blender treats different types of objects in different ways, and each of these can be enabled or disabled here For example, if you were to turn off the Solid button, no objects with solid faces would be rendered, leaving only the background

The other buttons can be used to disable rendering of Halos, Edges, Transparent (zTra) objects and the Sky background or BackBuffer image, on a Render Layer by Render Layer basis

Just below the render process buttons are two text fields: Light and Mat If the name of an object group is entered in the Light field, the Render Layer will use lamps from that group, ignoring any other lamps in the scene A material name entered into the Mat field will cause all objects in the Render Layer to be rendered as though they were temporarily linked to that material These fields are useful for doing test renders and special effects For example, you might need to substitute a simplified lighting rig and material to test object placement without actually replacing lamps and materials throughout your entire scene

Render Passes

Image:Dummy.png

RCD.05.4: Render passes buttons

At the bottom of the Render Layers tab are the controls for render passes As Blender renders an image, it performs a number of calculations that are combined to deliver the final color of the rendered pixel Render Passes allow you access to each stage of these calculations individually from within the Compositor For instance, you could separate the Diffuse, Specular, and shadow

calculations, and recombine them in the compositor By adjusting the way they mix, you could make the shadow darker or blur and lighten the specular highlights Using a work flow like this gives you the freedom to drastically improve and alter the look of the final output without re-rending, potentially saving enormous amounts of time

On new Render Layers, only two render passes are enabled:

- Combined, which delivers the final RGB and alpha results; and

- Z, the depth information of objects from the camera's viewpoint Each pixel in a render has a Z value, which refers to the distance between the camera and the face that was rendered If you look

in the Node Editor, you will see that the Render Layers node has three outputs: RGB, Alpha and

Z These outputs correspond directly to the Render Pass settings

Enabling any of the other pass buttons adds additional outputs to the associated Render Layer node

The other twelve passes are:

Vec: Provides vector motion data for the rendered geometry Mostly useful for calculating fast, vector-based motion blur

Nor: Provides the Normal information from objects in the render layer If looking at the output of this pass in a Viewer node, the strange colors are the visual encoding of the Normal

UV: The UV information from objects that have UV mapping This pass makes it possible to replace the colors on objects that use UV mapped textures, without re-rendering or changing the materials directly

IndexOb: You can assign any object an index value in the Object buttons and use this to create selection masks

Col: Provides an un-shaded color pass, as though everything had been rendered with a Shadeless material

Diff: The diffuse shading of objects, including colors, but without shadows or specular

highlighting

Spec: Specular shading

Shad: A pass representing shadowing information This pass is Multiplied with others to get a final image, so non-shadowed areas appear in white, with shadowed areas being progressively darker

AO: The result of Ambient Occlusion, without any materials applied

Refl: The reflection pass, if Ray is enabled on the Render panel and an object has a reflective material

Refr: Refraction, if Ray is enabled on the Render panel and an object uses ray refraction

Rad: A radiosity pass Radiosity is another method of lighting that is not covered in this book

If you would like to see the actual outputs from any of these passes, it's as simple as connecting their output sockets to a viewer node and re-rendering Of course, if you already rendered after the different passes were enabled, no re-render would be needed

Figure RCD.07, 08, 09, 10 The Col, Diff, Spec and Shad passes

If you want the practice of building your own, here's what to do:

In the Render Layers tab of the Render buttons, enable the Diff and Spec passes

Figure RCD.10.1: Enabling the Diff and Spec passes

Add a color Mix node (Add->Color->Mix), connecting the Render Layer node's Diff output socket to Mix's upper image input and the Spec output to the bottom image input

Create a View node with Add->Output->Viewer, and connect the output socket of the Mix node

to the Viewer node If something was already connected to the Viewer node, that connection will automatically be replaced by the new one you make

NOTE: The nodes systems doesn’t like loops or ambiguity, and will frequently delete

connections when you replace them with others, or warn you of problems should they occur

The Mix Node

The Mix node is one of the most frequently used and important nodes in the compositing system

It defines how color passes or images from two separate inputs will be blended into a single output

Figure RCD.11: The available mixing methods

A list of available mixing methods can be viewed by clicking the popup selector

In this case, choose Screen

Screen brightens an entire image, based on the image being mixed into it Light areas brighten more, with white turning the other image white Dark areas brighten less, with black leaving the image unaffected

Figure RCD.09: The Specular pass

The specular pass in the example is mostly black with some lighter areas, so it won't brighten the other image much We would like you to enhance the specularity, though, so you need a way to increase the brightness of the Spec pass It could be run through an RGB Curves node and

adjusted, but there is an easier way

The Fac (Factor) spinner on the Mix node controls the strength of the bottom image in the mix Values of 0 through 1 represent 0 to 100% The mix factor can go as high as 5, though, meaning that you can mix the Spec pass at 500% of its actual intensity

Set the Fac spinner on the Mix node to 4.77

Figure RCD.14: The current node network

Figure RCD.12, 13 Increased specularity following the Screen Mix node

As you adjust the mixing Factor, the Viewer node updates without having to re-render

The brass gauge now looks a lot shinier, but could still be better To do that, you'll apply a

common post-process effect: bloom

Bloom/Glow

Real highlights, such a specular reflection, tend to behave differently than mathematically

calculated highlights in a 3D package Light intensity in the real world can cover a huge range that our eyes find difficult to view As a result, very strong highlights can cause our eyes to actually overload in certain places, perceiving this dramatic contrast between light and dark as a kind of glow Adding this subtle effect can make a render look more authentic and is a simple way of adding believability without the extra processing requirements of more complex

raytracing algorithms

Load the file "CompositeStage3.blend" from the "examples" folder The nodes will appear empty until you render (F12) Also, it's okay that the dial appears blank right now The dial is seen through a refractive object and won't show until you make use of the Refract pass later

Figure RCD.15: The Bloom Node network Viewer nodes have been attached so you can easily examine the various stages

As you can see from the node tree, we have collapsed some of the nodes from the previous section using the controls described earlier That should make it easier to focus your attention on

the bloom effect Once you are happy with a section of a complex composite node tree, it is a good idea to collapse it like this to keep clutter to a minimum

Source of the Bloom

Although there are several ways to produce a bloom effect, the simple approach we've taken is to use the Specular pass again, brightening it and applying some blur before mixing it back into the existing image

Using RGB Curves to Brighten an Image

The network uses an RGB Curves node, taking its input from the same specular pass you used before In the basic back-shadowing tutorial, you used the RGB Curves node to invert and

colorize an image Here it is used to brighten the Spec pass by drawing the top right point of the Combined curve over three quarters of the way to the left

Figure RCD.16:

Here's a neat trick: enable the "Backdrop" button on the Node Editor's header Now, clicking on a Viewer node shows that preview right in the background of the Node Editor This is particularly

useful if you are working with your nodes in a Maximized window (Ctrl-Up Arrow/Down

Arrow), or if there is no room in your screen layout for a UV/Image Editor window The

backdrop preview may be moved around with Shift-MMB

Figure RCD.17: Backdrop enabled on the header This preview shows the result of the RGB Curves node on the Spec pass

Blurring an Image

After the RGB Curves node, you have a Blur node, which can be found under Add->Filter->Blur

Figure RCD.18: The Blur node with settings for the bloom effect

Although there are seven different blurring styles to choose from, two of the most commonly used are Gauss and Mitch

Gauss

Gaussian is a good, general purpose blur It provides an even effect across the image

Mitch

Mitchell-Netravali blur gives a more accurate effect for bright objects It does not reduce

highlights by evenly spreading them like Gaussian blur Because of that, this type of blur is excellent for working with highlights, as you are here

Of course, other blur methods like CatRom will produce similar effects, so the choice is yours With the speed of the Compositor, it's easy to switch between different blur methods to see which works best in your final production

to fake a camera blur effect, it is much more realistic

Gamma

This setting will give bright parts of the blur precedence over darker portions, instead of

averaging them This will usually lead to a brighter blur

Figure RCD.20: Using the Mix node in Screen mode again

Mixing the Bloom Effect

You need to mix this brightened and blurred image with the results of the diffuse and specular combination from earlier Notice how the title of the Mix node has changed to "Screen," making

it easier to tell the mix type at a glance, even on a collapsed node

Figure RCD.21: A new Mix node, in Screen mode

We have used a Screen Mix node (Add->Color->Mix), as once again you have to blend an image that needs to brighten another In this case, the Factor has been adjusted to 0.37, but try taking it

as high as 0.80 to see if you like it better