I'm working on a project using Lindenmayer systems(http://en.wikipedia.org/wiki/L-system) to simulate the animation of a tree growing. It uses recursion to determine how the branches and leaves of the tree appear. The program uses OpenGL and my programming language is C++.
Here's what I've defined my L-System with:
derivative length: 10 (my seed (called treeSeed) is set to 0 currently so that I could test the base scenarios of my recursions)
F--> G[-F][+F]GF
G --> GG
A few issues:
a) When I only call DrawTwig in DrawTree, the tree displays as it should. However, when I call DrawTree and DrawSeed at the same time, the window itself displays but I lose the rest of my scene. If I call DrawSeed before DrawTree, the sky and horizon display, but the tree trunk itself does not appear. Yet, when I comment out DrawSeed, the tree draws properly. I have a feeling it has to do with my coordinates but I am not sure.
b) I am trying to complete the GroworShrink method. When completed, it will determine whether the tree shrinks or grows during the animation. However, I am not sure how to complete it. I have a for loop there to iterate through the branch points, but I do not know what to add to actually make it grow or shrink.
#include <math.h>
#include <windows.h>
#include <GL/gl.h>
#include <glut.h>
int treeSeed = 0;
float branchAngle = .2618;
//void GroworShrink()
//{
//
// if(treeSeed <=10 && treeSeed != 0)
// {
// int i;
// for(i = 0; i <=10 ; i++)
// {
//
//
//
//
// }
//
// }
//else
//}
//void treeAninmation()
//{
//
// glutPostRedisplay();
//}
/*
Draws a leaf on the branch.
If the seed axiom is at zero,
a new leaf is drawn. Otherwise,
the branch shrinks to accomodate
existing leaves.
*/
void DrawLeaf()
{
if(treeSeed==0)
{
glBegin(GL_QUADS);
glColor3f(0.0f,1.0f,0.0f);
glVertex2f(-0.05, -40.5);
glVertex2f(-0.05, -20.5);
glVertex2f(-0.02, -40.5);
glVertex2f(-0.02,-20.5);
}
/*else
{
GroworShrink();
DrawTwig(treeSeed-1);
glPushMatrix();
glRotate(branchAngle,1.0f,0.0f,0.0f);
DrawLeaf(treeSeed-1);
glPopMatrix();
glPushMatrix();
glRotate(branchAngle, );
DrawLeaf(treeSeed-1);
glPopMatrix();
}*/
}
void DrawTwig()
{
/*
Draws trunk of tree
Represents base scenario of
recursion
*/
if(treeSeed==0)
{
glLineWidth(5.0);
glBegin(GL_LINE_STRIP);
glColor3f(0.60f,0.40f,0.12f);
glVertex2f(-0.10, -80.5);
glVertex2f(-0.10, -100.5);
glEnd();
}
/*else
{
GroworShrink();
DrawTwig(treeSeed-1);
}*/
}
/* Draws the tree with leaves *
Uses recursion to draw tree structure
Relies on L-System formula in order
to produce a tree
*/
void DrawTree()
{
DrawTwig(treeSeed);
//DrawLeaf(treeSeed);
}
/* Draws the horizon, the sky, and the ground*/
void RenderScene(void)
{
// clears color buffer
glClear(GL_COLOR_BUFFER_BIT);
/*
//GLfloat y;
GLfloat fSizes[2]; // Store supported line width range
GLfloat size; // Store supported line width increments
*/
//The horizon lies in the xy plane
glBegin(GL_LINE_STRIP);
glColor3f(0.0f,0.0f,0.0f); //sets color of horizon to black
glVertex2f(-135.0,0.0);
glVertex2f(135.0,0.0);
glEnd();
//The sky lies in the xy plane
//Starts at horizon line,
//goes upwards to height edge of screen,
//and goes rightwards to width edge of screen.
glBegin(GL_QUADS);
glColor3f(0.0f,0.0f,1.0f);
glVertex2f(135.0, 0.0);
glVertex2f(-135.0, 0.0);
glVertex2f(-135.0, 100.0);
glVertex2f(135.0,100.0);
glEnd();
DrawTree();
glFlush();
}
void SetupRC(void)
{
glClearColor(1.0f,1.0f,1.0f,1.0f);
}
void ChangeSize(GLsizei w, GLsizei h)
{
GLfloat aspectRatio;
//prevents divison by zero
if(h ==0)
h = 1;
//set Viewport to window dimensions
glViewport(0,0,w,h);
// Reset coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Establish clipping volume (left, right,bottom,top,near,far
aspectRatio = (GLfloat)w/(GLfloat)h;
if (w <= h)
glOrtho (-100.0, 100.0, -100/aspectRatio, 100/aspectRatio,1.0,-1.0);
else
glOrtho (-100.0 * aspectRatio, 100.0 * aspectRatio, -100.0, 100.0, 1.0, -1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void main(int argc, char **argv)
{
glutInit(&argc, argv);
/* Testing basic display functions for now */
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(1000, 1000);
glutCreateWindow("falling leaves");
glutReshapeFunc(ChangeSize);
glutDisplayFunc(RenderScene);
//glutIdleFunc(treeAnimation);
//glutDisplayFunc(DrawTree);
SetupRC();
glutMainLoop();
}