Android 3D engine research 2

In the previous article, we can see that a cube can be displayed on the screen through a small amount of code, which is equivalent to the hello World Program in min3d. However, for OpenGL ES programming, the data we usually need to process is a triangle. Unfortunately, these details are hidden using engines like min3d. Here, we manually generate a cube placed on the origin, giving vertices, triangles, and normal vectors, which are then displayed by the min3d engine. This gives us a better understanding of how OpenGL ES works. The specific implementation code is as follows:

Public mgnavobject (Boolean useuvs, Boolean usenormals, Boolean usevertexcolors ){
Super (4*6, 2*6, useuvs, usenormals, usevertexcolors );
Float width = 1.0f/2;
Float Height = 1.0f/2;
Float deepth = 1.0f/2;
Float textureu = 0.0f;
Float texturev = 0.0f;
Float normalx = 0.0f;
Float normaly = 0.0f;
Float normalz = 0.0f;
Short colorr = 0;
Short colorg = 0;
Short colorb = 0;
Short colora = 0;
// Display the right Cube:
// Area number: Starting from the front, the area number is 1 (Before), 2 (right), 3 (after), 4 (left), 5 (top), 6 (lower)
// Vertex number: Start from the top left corner, clockwise 1, 2, 3, 4; followed by four to five, two to six, three to seven, four to eight
// For example, if vertex 1 is in front of f1p1 and f5p1 is in front of vertex 1
// 1. front
NormalX = 0f;
NormalY = 0f;
NormalZ = 1.0f;
// 1.1. Add the front right top triangle
Short f1p1Idx = vertices (). addVertex (-width, height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Short f1p3Idx = vertices (). addVertex (width,-height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Short f1p2Idx = vertices (). addVertex (width, height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Faces (). add (f1p1Idx, f1p3Idx, f1p2Idx );
// 1.2. Add the Lower Left triangle to the front
Short f1p4Idx = vertices (). addVertex (-width,-height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Faces (). add (f1p1Idx, f1p4Idx, f1p3Idx );
// 2. Add the right side
NormalX = 1.0f;
NormalY = 0.0f;
NormalZ = 0.0f;
// 2.1. Add triangle slices 2, 3, and 7
Short f2p2Idx = vertices (). addVertex (width, height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Short f2p3Idx = vertices (). addVertex (width,-height, deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Short f2p7Idx = vertices (). addVertex (width,-height,-deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Faces (). Add (f2p2idx, f2p3idx, f2p7idx );
// 2.2. Add a triangle, 5
Short f2p5idx = vertices (). addvertex (width, height,-deepth,
Textureu, texturev,
Normalx, normaly, normalz,
Colorr, colorg, colorb, colora );
Faces (). Add (f2p2idx, f2p7idx, f2p5idx );
// 3. Add the following
Normalx = 0.0f;
Normaly = 0.0f;
Normalz =-1.0f;
// 3.1. Add a triangle, 6, 7, and 8
Short f3p6idx = vertices (). addvertex (width, height,-deepth,
Textureu, texturev,
Normalx, normaly, normalz,
Colorr, colorg, colorb, colora );
Short f3p7idx = vertices (). addvertex (width,-height,-deepth,
Textureu, texturev,
Normalx, normaly, normalz,
Colorr, colorg, colorb, colora );
Short f3p8Idx = vertices (). addVertex (-width,-height,-deepth,
TextureU, textureV,
NormalX, normalY, normalZ,
ColorR, colorG, colorB, colorA );
Faces (). add (f3p6Idx, f3p7Idx, f3p8Idx );
// 3.2. Add triangle film 6, 8, 5
Short f3p5Idx = vertices (). addVertex (-width, height,-deepth,
TextureU, textureV,
NormalX, normalY, normalZ,