### 3D Polygon Reduction Tutorial

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**Sat Nov 30, 2002 3:29 pm**This tutorial is meant specifically for Andy to use with Cinema 4D, but any other onlookers are welcome to follow along and ask any questions. I had mentioned in my Escape Velocity thread that your Ocean Patrol Fighter could use some polygon cleanup. This thread is going to outline why you would want to do this and the steps you would take in doing it.Part One: Why Boolean Operations Are BadAt first, the boolean tool in C4D may appear to be a godsend. It allows you to take primitives (like cubes and spheres) and objects that you may have created manually and combine them or use one to carve a section from the other. When dealing with relatively simple scenes, using boolean operands is okay. They are okay to use in large scenes too in only a few cases. When booleans are applied to certain types of meshes, they can easily increase the complexity ten-fold.Here is one such example where using a boolean can greatly increase a mesh's complexity. I needed to carve some vents in the top hinge covers on the shoulders of my Dai-X model. Here is the original mesh that I had made by hand:I added to this a single null object with 6 simple cubes as its children. I scaled them and positioned them like this:I dropped the original mesh and the null with the cube children into a boolean object. I selected that boolean and chose the function "current state to object" and then "connect" to create a new complete mesh. This is what that mesh looks like:On a duplicate file, I took the original mesh and manually knifed the polygons, deleted ones, and bridged points to points to create new polygons. This is how that final mesh looks:Then end results look identical when rendered. As you can immediately see, though, the computer's boolean calculations are quite a bit inefficient. In fact, my handmade mesh is about five times more efficient than the computer-calculated mesh. The original mesh has 44 points and 44 polygons. The computer's mesh has 936 points and 924 polygons. The mesh I made has 156 points and 182 polygons. Now, this is a single boolean operation on a relatively tiny piece of a much larger scene. Imagine how rapidly the complexity would grow if I used booleans in *all* places I need to subtract from a mesh.Sure, a few hundred extra polygons don't matter in something small like this, but when you start working with thousands and tens of thousands of polygons and your mesh balloons into hundreds of thousands and millions of polygons when using these booleans, even the fastest CPUs will slow down when it comes to the basic screen display and then rendering the raytraces.So, what are the steps for cutting into meshes like I did? I'll cover a few techniques in the next section I write for this thread. In this example, I used the polygon selection tool, knife tool, point selection tool, and bridge tool. I'll explain them along with the extrude and extrude inner tools. These are the basic tools for manipulating meshes by hand. I have built almost everything of mine that you have seen so far by using these tools alone on the basic primitives like cubes, cylinders, and spheres.(Edited by Bradster at 3:40 pm on Nov. 30, 2002)