In this article I will explain in simple terms, what goes behind the 3D animation that you watch in movies and what makes it different from conventional two dimensional animation.
What is that extra 3rd dimension? Take a piece of paper and sketch a simple figure on it (a cat, a dog or anything that comes to your head). Lets say it is a cat and it is facing you from that sheet of paper. So you have the front view of the cat in front of you. Suppose if you feel that you want to see the cat from a side, will it help if you rotate the paper or flip it? No. Why? It is simply because the sketch you have drawn has the 3rd dimension missing.
Every real world object that you see around has a 3rd dimension and that is the reason why you can take it and rotate it to watch it from different angles. The sketch you have drawn had a length and a width, since the paper you used to draw also had a length and a width. But it lacks a thickness (3rd dimension) and hence your sketch also didnt have that extra dimension.
Suppose instead of sketching your imagination down on the piece of paper, you decided to sculpt it on a handful of clay. Since the medium you used (clay) had volume, you had to define the cats shape from all angles during the sculpting. Hence you unknowingly added that 3rd dimension to it and that is the reason you have the freedom to rotate it any way you want.
How conventional 2D animation works:
Before computers started playing their indispensable roles in the animation industry, everything was done manually by animators, who were essentially artists. They would create a series of slides having images on it, where each slides image is the continuation of the previous one in the sequence. For example if an animator wanted to simulate a ball falling down, they would create a sequence of slides where first slide would portray the ball at the top. The next slide will show the ball, may be 1 cm lower than that in the first slide. In the next one, again lower and so on, till the last slide shows the ball hitting the ground. When the whole sequence of slides are shown in front of the viewer in a fast rate, it creates the feeling of the ball falling down.
The whole process was tedious and time consuming. When computers came into play, the frame redrawing works had been minimised since, copying and pasting duplicate elements between successive frames was very easy with the computers aid. The artist has to make only the necessary changes that should exist between successive frames. As technology advanced, softwares evolved that again minimised the work of a 2d animator, in such a way that several things started getting automated. Using motion tweening and other techniques, an animator can set the initial position or shape of an object and then its final position and shape and the computer would generate the intermediate frames automatically. The artist even has the freedom to make corrections to that.
What was missing in 2D animation?
The 2D animation always lacked the essence, since all the real-world sceneries and objects are 3D and when they gets transformed to 2D, they lose their reality. Later stage cartoons started to simulate the 3D effect by using gradients, and varying highlights, but it required huge extra effort from the part of the artist.
How 3D Graphics works:
The stages in 3D animation are more in number compared to the 2D animation. The first part of 3D animation starts with character sketching and 3D modeling. In the next stage the characters are rigged for animation. In the next stage they are animated. This is in fact a too compact form of what happens in the background. Lets see each of them in a little detail.
· Character sketching: This is the stage where an artist sketches how the character should look from various angles. Usually the sketch will be done on paper or canvas. As many variations in poses are created so that it would help the 3D Modeler to sculpt a 3D Model out of it.
· Character Modeling: A 3D artist, who is expertised in a 3D modeling and animating tool, will examine the sketches and starts sculpting the figure using his imagination and skill. I used the word sculpting because the process is much similar to the real sculpting we do with raw materials like clay. The software tool that the artist uses provides various approaches to perform the modeling. Usually organic modeling techniques like Polygonal Modeling (a polygon is subdivided to get the desired shape), NURBS modeling (curves are arranged to create a surface flowing through them), Subdivisional Modeling (A hybrid blend between polygonal modeling and NURBS modeling) are used. In these modeling techniques, the 3D modeling artist will sculpt out the characters shape in 3D using a set of tools provided by the 3D modeling software, by following any of the above mentioned approaches.
The 3D Model obtained finally will be in an editable form and the model will be dependent on the approach used. For example a NURBS technique will yield a 3D Model in the NURBS representation (curves and surfaces). Once the modeling is complete, the artist converts it into the basic polygonal mesh (vertices alone). The polygonal mesh is nothing but a huge number of polygons that are arranged so as it forms the whole character. This conversion to polygonal mesh offers many advantages like faster rendering speed, and multi-software compatibility.
· Scene building: In addition to the characters the animation will have an environment and related objects. The 3D modeling software provides methods to simulate the environment, model the world , sun etc. For example in the 3d modeling and animation software called Maya, the artist have a huge library of Paint effects that contains Trees, leaves etc from which he can drag and drop into a scene and customize it in accordance to needs.
· Texturing: During this stage, all the objects in the scene are given suitable textures using the 3D animation tools specific facilities. Some tools provide only facilities for mapping an image texture on to the 3d model, whereas advanced tools even let you paint on the 3d meshs texture surface.
· Lighting and Camera setup:
This process is much like that in a real world movie making. The 3D animation software provides different types of lights which you can place in the scene in any direction you want. You can adjust the intensity, cone angle or even the shadow cast by the individual lights. Camera also is the replica of the real camera we use for shooting. We can place multiple cameras in a scene; adjust its focal length, aperture size and almost every parameter that you can find in a real camera.
· Animation: Once the static elements have been set, the 3D artist applies motion to them. This process, called animation is performed by setting keyframes. In order to animate a ball falling, the animator would set the first key frame at say 0th second with the balls position at the initial top position. He would set the next key at say 5th second with the balls position touching the ground. The 3D animation software interpolates the balls falling action between the 0th and 5th seconds. The animator can customize the interpolation behavior using graphs or by setting intermediate keys.
In Character animation, similar principles are applied. The skeleton will be animated by the animator and the 3d mesh skinned to the skeleton gets animated automatically. Character animation is often aided by plug-in tools (e.g.: biped) that has been created specifically for creating character animation sequences like walking or running cycles. The various scene elements, cameras and lights are animated using basic key-frame animation, based on the story board requirements.
Once the scenes are animated, it will undergo a process called rendering, in which the 3d representation is converted to a video format, which can be read and edited using professional video editing software.