Shadows can play an important role in the composition of your image. To fix this, you may need to change the angle of your shadows, or might even have to use a second version of the character without the cheat as a shadow object (shadow objects are discussed below). For example, if the animator has stretched a character's arm to an extra long length in order to bring the hand into the foreground, that cheated pose might look believable from the point of view of the camera, but look strange where the character's shadow is visible on the side wall. Also, be sure that any cheats that the animator has created don't look strange from the shadow's perspective. The outline of what you see-the profile of the subject from the light's point-of-view-shows you the shape that will be rendered as the shadow.īe careful that no part of the character is much closer to the point-source or spotlight, lest it become disproportionately enlarged in the shadow. Most 3D programs enable you to view the scene from a light's point-of-view, as an aid to positioning and aiming the light. You can think of the light casting shadows as something like a second camera, with its own angle of view and perspective on the character. In Figure 3.2, the woman's profile is brought out by a shadow, without which we would see only the front of her face.įigure 3.2 The shadow reveals a character's profile, which otherwise would not be seen in the rendering.
In addition to spatial relationships, a well-placed shadow can also disclose new angles on a subject that otherwise might not be visible. As you look around the room, your eye interprets small differences in the shadows almost instantly, determining the spatial relationship between the furniture and the floor. At a glance, you can probably tell whether each piece is directly touching the floor or is held above the floor by wheels or casters, just by looking at the shadows each piece of furniture is casting. If you are reading this book indoors, look around the room at all the places where furniture meets the floor. Animation that was created and approved without shadows may need to be fixed once it has been test-rendered with shadows and any flaws are made visible. When a scene is rendered with shadows, the shadows can reveal mistakes and inaccuracies in your animation, such as if a character's feet are floating above the ground instead of planted firmly on it. The way shadows visually indicate spatial relationships is both a blessing and a curse. The most basic use of shadows is to show spatial relationships between objects, as in the right side of this figure.
On the right side of the figure, the added shadows reveal how close some of the balls are to the back wall, when a ball is on the ground, and when two balls are near each other.įigure 3.1 On the left side, you cannot tell how close the large upper ball is to the back wall. Without shadows, you can't tell exactly where each ball is located. For example, compare the scene in Figure 3.1 before and after shadows are added. When objects cast shadows onto each other, the spatial relationships between the objects are revealed. Here are some of the visual functions that shadows serve in cinematic images and computer graphics.
But shadows can often reveal things that otherwise would not have been seen. People commonly think of shadows as obscuring and limiting vision. This chapter will explore both the visual and the technical sides of shadows and occlusion in 3D graphics.
Making the best choices of shadow-casting algorithms, building up a bag of tricks to cheat and manipulate your shadows, and knowing how to optimize your shadows for the best possible rendering speeds are essential skills for any 3D artist. Besides their artistic importance, rendering shadows is a key technical area to master. Shadows can add richness to the tones and shading of your image, tie elements together, and improve your composition. You can think of all of your illumination as one half of your lighting design, and shadows as the other, equally important half. Setting up shadows takes just as much time and attention as setting up lights. Digital Lighting and Rendering, 2nd Edition