Essential Blender- P25 ppsx

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. Recombining Passes For the first part of this exercise you will recombine the Diffuse and Specular passes to make the brass of the gauge's body a little brighter and shinier. You can either follow the simple instructions to set this up yourself, or if you prefer, load up the completed stage for examination. The file "CompositeStage2.blend" can be found in the "examples" folder.