How to draw a Cube with Triangle Strip

waltercorneli

Anyone knows how to make a cube with triangle strip? Something like this: http://i.imgur.com/kK6fY.png

jeremydouglass

Transformations such as translate(), rotate(), and scale() do not work within beginShape() -- beginShape() reference

This means if you specifically want to use the 2D TRIANGLE_STRIP, one way of doing it is by rotating around X Y and Z in the space and drawing a series of faces made out of rows of triangle strips.

void drawTriangleSheet(int cols, int rows, float w, float h){
  pushMatrix();
  translate(-cols*w/2,-rows*h/2);
  for (int y = 0; y < rows; y++) {
    beginShape(TRIANGLE_STRIP); 
    for (int x = 0; x <= cols; x++) {
      vertex(x*w, y*h);
      vertex(x*w, y*h + h); 
    }
    endShape();
  }
  popMatrix();
}

jeremydouglass

For those interested in this particular problem (using TRIANGLE_STRIP or QUAD_STRIP to build cubes) I wrote a demo sketch.

It isn't efficient or compact -- rather, it is meant to walk through the logic of assembling a face out of strips, then creating pairs of faces, then building a full cube out of three pairs. It flips between quads and triangles every other second. Remove the "timedTumble" and add the peasyCam library to interact with the shape.

/**
 * Shape Strip Cube
 * 2016-12-14 Jeremy Douglass - Processing 3.2.3
 * https:// forum.processing.org/two/discussion/18996/how-to-draw-a-cube-with-triangle-strip
 **/

int sheetType;

void setup() {
  size(500, 500, P3D);
  stroke(0,255,0);
  noFill();
}
void draw() {
  background(0);
  translate(width/2,height/2);
  //// spin camera
  timedTumble(40);
  //// draw cube
  sheetType = (second()%2==0) ? TRIANGLE_STRIP : QUAD_STRIP;
  drawCube(10, 28);
}

void drawCube(int units, float size){
  pushMatrix();
    //// front and back
    drawFacePair(units, size);
    rotateX(HALF_PI);
    //// top and bottom
    drawFacePair(units, size);
    rotateY(HALF_PI);
    //// left and right
    drawFacePair(units, size);
  popMatrix();
}

void drawFacePair(int units, float size){
  pushMatrix();
    translate(0,0,units*size/2);
    drawSheet(units, units, size, size);
    translate(0,0,-units*size);
    drawSheet(units, units, size, size);
  popMatrix();
}

void drawSheet(int cols, int rows, float w, float h){
  pushMatrix();
  translate(-cols*w/2,-rows*h/2);
  for (int y = 0; y < rows; y++) {
    beginShape(sheetType); 
    for (int x = 0; x <= cols; x++) {
      vertex(x*w, y*h);
      vertex(x*w, y*h + h); 
    }
    endShape();
  }
  popMatrix();
}

//// Timed 3D tumble, rotations cycle back to start every `duration` seconds
void timedTumble(float duration){
  duration = duration*1000; // milliseconds
  float spin = TWO_PI*2 * (millis()%duration)/duration;
  rotateX(spin);
  rotateY(spin/2);
  rotateZ(spin/8);
}

This was the original reference image for the question:

...and this is the sketch output:

Lexyth

Wouldn't this be better, since it would be only one Shape, and not multiple, or doesn't this work?

Edit: doesnt work correctly, but i'll leave it here, just in case someone was going to try the same.(Could still be used, but only if individual triangles arent visible);

    void drawTriangleSheet(int cols, int rows, float w, float h){
    *Boolean L = true;
      pushMatrix();
      translate(-cols*w/2,-rows*h/2);
        beginShape(TRIANGLE_STRIP); 
      for (int y = 0; y < rows; y++) {
    *if (L == true) {
        for (int x = 0; x <= cols; x++) {
          vertex(x*w, y*h);
          vertex(x*w, y*h + h); 
        }
    *} else {
     *   for (int x = cols; x > 0; x--) {
     *     vertex(x*w, y*h);
     *     vertex(x*w, y*h + h); 
     *   }
    *}
        endShape();
      }
  popMatrix();
}