How the CINEMA 4D render engine works

A 3D render engine is a very complicated piece of software that's designed to simulate how light and how cameras and how other types of objects behave in the real world. Now when you hit the Render button in Cinema 4D, some very important things happen. Now I have a simple scene here of a green light shining down on the sphere and I've got a camera pointing at that, and I'm going to hit the Play button here in the interface. Now when you hit the Render button, a couple of things happen. The first thing that happens is, from the point of view of the camera and from the point of view of the light source, the render engine sends out these little mathematical probabilities called rays, and those rays are designed to figure out what types of pixels are going to be drawn in the frame.

Let's look through the camera by pressing the active Camera icon and we'll get this cute little animation that pops us right into the point of view of the camera. And you can see that from the camera's point of view, these lines represent the rays. There's really a lot more rays in that that go out, but these are designed to simulate that. The white rays in the scene represent the rays from the camera's point of view. The green rays in the scene represent the light's point of view. The whole point of the rays is to report back to the render engine what they encounter in the scene, and to tell the render engine what type of pixel they're supposed to draw there.

So if a ray goes out into the world and strikes a polygon then it reports back to the render engine hey! Render engine, I have found a polygon at this location. It has a material on it that looks like this. It had lights shining on it from this angle. Therefore, you should draw pixel at this location on the screen of this value. Now that happens over and over again for every pixel in the frame. Now some of the rays will travel off to infinity and not report back. For all of those rays, you get black on the screen and that determines what your background looks like. Some of the rays will strike the ball from the camera and some of the rays will strike the ball from the light.

The combination of those two reports is what tells the render engine what type of sphere and what types of pixels to draw on frame. I'm going to click the Render and Active View button. When I click that, you can see that we have a perfectly drawn sphere with a green light shining on it. The sphere's material is actually gray. The render engine knows to draw it green because the gray material on the sphere combines with the green light from the light source to make for a green sphere. Once the render engine has drawn those pixels, then you have to get the pixels out of the application in order to do something with them in another compositing program like Photoshop or After Effects or Nuke.

In order to do that, the render engine has to take those pixels and convert them into a file format. Cinema 4D can write down a lot of different file formats. The most popular ones are QuickTime and Photoshop. However, regardless to the file format, the render engine is still going to go through that same motion everytime you hit the button. Keep in mind that I'm tremendously over simplifying the actual process of rendering an image. I'm doing this to help you understand how it works. How the render engine works really helps you to understand how the lights behave and how the materials behave and how object should be shaped.

All of these ideas combine together to help you produce your images.