Code: 3d_underwater_world/seaweed.cpp

This is an example OpenGL SDL application which creates an animated 3D underwater world (screenshot), with "Thunderbird 4" with headlights moving on a spline path, a randomly generated sand terrain, sunken ship/submarine/treasure chest models, and swaying fish and seaweed. It is designed to demonstrate basic OpenGL features, and the structure is as follows:

#include "worldobjects.h"
#include "vectors.h"

#define MIN_X 0.0
#define MIN_Y 0
#define MIN_Z 0.0
#define MAX_X 100.0
#define MAX_Y 0
#define MAX_Z 100.0

#define BLADE_COUNT 500
#define MAX_HEIGHT 10

// calculate a random float between
// 0.0 and ran.
inline GLfloat randf(GLfloat min, GLfloat max) {
    // calculate between 0 and 1
    int ir = rand() % 1000;
    GLfloat v = ((float)(ir) / 1000.0f);
    // change to range
    return (v * (max - min)) + min;
}

// constructor
GrassObject::GrassObject()
{
    // center position
    pos.x = randf(MIN_X, MAX_X);
    pos.y = randf(MIN_Y, MAX_Y);
    pos.z = randf(MIN_Z, MAX_Z);
    // height
    h = randf(4, MAX_HEIGHT);
    // grass amount
    count = rand() % BLADE_COUNT;
    // create blades
    loc = new Vec3[count];
    now = new Vec3[count];
    shades = new float[count];
    Mat4 m;
    for (int i = 0; i < count; i++) {
        // work out random pos
        Vec3 top(0, randf(h/2,h), 0);
        m.setI();
        m.rotate(randf(-50,50), 1, 0, 0);
        m.rotate(randf(-50,50), 0, 0, 1);
        m.transform(&top);
        // remember pos
        loc[i].set(&top);
        now[i].set(&top);
        // random shade
        shades[i] = randf(0.5, 1);
    }
}

GrassObject::~GrassObject()
{
    delete loc;
    delete shades;
    delete now;
}

// draw
void GrassObject::drawInternal()
{
     glBegin(GL_LINES);
     for (int i = 0; i < count; i++) {
         // shade
         glColor3f(0, shades[i], 0);
         // start at bottom
         glVertex3f(0, 0, 0);
         // to top coordinate
         glVertex3f(now[i].x, now[i].y, now[i].z);
     }
     glEnd();
}

// simulate
void GrassObject::simulate(GLfloat dT)
{
     time += dT;
     // make blades wave
     for (int i = 0; i < count; i++) {
          now[i].x = loc[i].x + sin(time);
      }
}

3D Underwater World (using OpenGL and SDL)

seaweed.cpp