Chapter 9. Intermediate 3D Graphics

Once you’ve got OpenGL drawing basic 3D content, you’ll likely want to create more complicated scenes. In this chapter, you’ll learn how to load meshes from files, how to compose complex objects by creating parent-child relationships between objects, how to position a camera in 3D space, and more.

This chapter builds on the basic 3D graphics concepts covered in Chapter 8, and makes use of the component-based layout shown in Creating a Component-Based Game Layout.

Loading a Mesh

Problem

You want to load meshes from files, so that you can store 3D objects in files.

Solution

First, create an empty text file called MyMesh.json. Put the following text in it:

{
    "vertices":[
        {
            "x":-1, "y":-1, "z":1
        },
        {
            "x":1, "y":-1, "z":1
        },
        {
            "x":-1, "y":1, "z":1
        },
        {
            "x":1, "y":1, "z":1
        },
        {
            "x":-1, "y":-1, "z":-1
        },
        {
            "x":1, "y":-1, "z":-1
        },
        {
            "x":-1, "y":1, "z":-1
        },
        {
            "x":1, "y":1, "z":-1
        }

    ],
    "triangles":[
        [0,1,2],
        [2,3,1],
        [4,5,6],
        [6,7,5]
    ]
}

Note

JSON is but one of many formats for storing 3D mesh data; many popular 3D modeling tools, such as the open source Blender, support it.

This mesh creates two parallel squares, as shown in Figure 9-1.

The mesh.
Figure 9-1. The mesh

Next, create a new subclass of NSObject, called Mesh. Put the following code in Mesh.h:

#import <GLKit/GLKit.h>

typedef struct {
    GLKVector3 position;
    GLKVector2 textureCoordinates;
    GLKVector3 normal;
} Vertex;

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