Pixar in a Box
Explore the rendering process through a case study with a scene from the Pixar film Monster's University. Each pixel color is determined by finding the intersection point between a ray from the camera and the scene. The color and light response of surfaces (diffuse and specular) play a role in the final image!
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- Why is it that in defuse you can't see the 3D effect but you can in specular?(7 votes)
- The diffuse component of the render is just the object's color, without any lighting information. Even if all of the lights in the scene are turned off, the diffuse component will be the same.
The specular component, on the other hand, relies entirely on the lights. If the lights are off, spec is black.
Our perception of an object's shape in three dimensions is strongly affected by the light that falls on the surface. In traditional art and photography, they use the term "modeling" to describe how the interplay of light and shadow create a perception of volume. We can get some idea of shape from the warping of texture around an object. Look at the color pass at about1:28in the video—you can see the warping I'm talking about in the edge of the desk's top and the stool. Mike's texture is a little too low-contrast to be able to see well. That information is not as strongly weighted in our brains as light and shadow, though, so the color pass looks flat, but the specular pass looks 3d.(7 votes)
- Is it just me or do you think movies would be way more interesting with just specular light.(2 votes)
- In the first few videos, we discussed the basic job of a ray tracer: determine the final pixel color for each pixel in an image. Let's look at a "real-world" example from Monster's University. First, for each pixel, we need to find the intersection point between a ray, starting at the camera, shooting through a pixel, and shooting into the scene. The next step is to ask, "What color is each of these surfaces?" It turns out that color, alone isn't very interesting to look at, right? Next, we need to determine how the surface will respond to light. As we discussed earlier, the two basic components of surface response are called diffuse and specular. This is a picture of how diffuse, or dull, each object is. Where this image is bright white is gonna be where the dullest surface in the scene is. For example, the hat is really dull. And this is a picture of how specular, or shiny, each object is. Now, from this image, can you tell where the main light source is? Pause the video now, if you need some more time. The light source is off to the left side of the screen. You can actually see it reflected in Mike's eye, here. Now, each object in the scene receives directing lighting, which we see here in these images of diffuse and specular. But they also received indirect lighting, which is light bouncing off of other objects in the scene. So what happens when we put all these calculations together? It's kind of magical, right? That's what we do. It's math, but used to create magic!