/* A demo of texture-mapping onto a cylinder, aligning the image two
   different ways.  There is no lighting in this demo, so no need for
   normals on the cylinder.  The texture is decaled on, so the color of
   the cylinder is unimportant.

Scott D. Anderson,
original, Fall 2002 
Adapted and simplified for TW, Fall 2003
*/

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <tw.h>

void textureInit(char* imgfile) {
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

    twPPM_Tex2D(imgfile,true);
}

const float CylinderRadius = 1;
const float CylinderHeight = 6;
bool Long = true;                // whether the parameter is parallel to the axis
int Sides = 4;                        // the number of sides to the cylinder

/* ====================================================================
   This cylinder has texture coordinates on the vertices.  It has s around
   the circumference (mapping s:0-1 as angle:0-2pi).  It has t going along
   the axis.  The axis is aligned with the z axis. Use transformations if
   that's not what you want. The bottom and top also have textures mapped
   onto them, just to show the distortion one would get. */

void cylinder(GLfloat radius, GLfloat height, int steps) {
    int i;
    GLfloat float_steps=(GLfloat) steps;
    GLfloat theta, x, y, p, cosine, sine;

    glEnable(GL_TEXTURE_2D);
    glBegin(GL_QUAD_STRIP);
    for(i=0; i<=steps; ++i) {
        p = i/float_steps;        // the parameter
        theta = p*2*M_PI+M_PI/4;
        x = radius*cos(theta);
        y = radius*sin(theta);
        if(Long)
            glTexCoord2f(p,0);
        else
            glTexCoord2f(0,p);
        glVertex3f(x,y,0);
        if(Long)
            glTexCoord2f(p,1);
        else
            glTexCoord2f(1,p);
        glVertex3f(x,y,height);
    }
    glEnd();
}  

void display() {
    twDisplayInit();
    twCamera();
    glPushAttrib(GL_ALL_ATTRIB_BITS);

    glEnable(GL_TEXTURE_2D);
    cylinder(CylinderRadius,CylinderHeight,Sides);

    glPopAttrib();
    glutSwapBuffers();
    glFlush();
}

void keys(unsigned char k, int, int) {
    switch (k) {
    case '+': Sides++; break;
    case '-': Sides = Sides > 3 ? Sides-1 : 3 ; break;
    case 'l': Long = !Long; break;
    }
    glutPostRedisplay();
}

int main(int argc, char** argv) {
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
    glutInitWindowSize(500,500);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    twBoundingBox(-CylinderRadius,CylinderRadius,
                  -CylinderRadius,CylinderRadius,
                  0,CylinderHeight);
    twMainInit();
    if(argc < 2 ) 
        textureInit("USflag.ppm");
    else
        textureInit(argv[1]);
    twKeyCallback('+',keys,"Increase number of Sides");
    twKeyCallback('-',keys,"Decrease number of Sides");
    twKeyCallback('l',keys,"toggle the orientation of the texture");
    glutMainLoop();                   
    return 0;
}