theonlycheshirecat  asked:

Why does rendering take so long?

Well, it doesn’t have to, but it depends on the complexity of the thing you’re rendering. When you’re working with 3D, you don’t see light, or shadow, or reflections, or any details like that. You’re working with just colors and shapes. Depending on how many lightsources you have, the computer will have to calculate the directions of shadows, and the distance to the light, how much softer the shadow gets over distance. Also, how the light hits the objects, and how that changes the color of the object, depending on intensity of the light and the distance to the source. For every lightsource.

And then multiply that through every reflective surface. Every shiny thing. Many things are reflective, but not like a mirror where everything is perfectly clear. Most materials give a softer reflection that gets more and more blurry, as distance to the reflected object increases.

And then you have refraction, see-throughness of things like glass or ice and stuff. When the light hits something behind glass, it needs to run all those calculations above, AND then correctly distort that based on the shape and parameters of the glass-object. Say you look at something through a glass vase, that stuff gets all distorted and twisted. BUT that stuff still needs to have proper light, shadow and reflections BEFORE it gets refracted in the glass vase. And then, some glass isn’t even 100% clear, like ice, you can still see through it but things get blurry and muddled, which adds another layer of calculation.

Take something like South Park for example, that’s created with flat shapes in Maya, and I’m willing to bet that rendering doesn’t take THAT long for them to render. Because it’s simple, flat, maybe one lightsource with hard shadows, no reflections, just colors and some shadows. There are relatively few things to calculate. Compared to Finding Nemo which has hundreds of different materials and colors, UNDER WATER with light rippling through the surface above, casting soft moving shadows, etc. etc. I use Finding Nemo as an example, because I happen to know that the underwater-scenes of that movie took between 60-90 HOURS to render PER FRAME. That’s 24 frames per SECOND.

That’s why rendering takes so long :P