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Strange Face Behavior from Triangle_Fan

[1 Reply]
- 09-Feb-2012 03:38 PM
- Forum: Contributed Library Questions
I am trying to use triangle fan to cap the ends of the cylinder I am creating. I have simplified the code below to what is causing the problem. For some reason triangle_fan wants to create a "phantom" face. 15 faces are drawn but the count reads 16.
This can be isolated to show the "phantom face" if change line 37 to read: Somehow it is drawing a face from only two points.
1. for ( int i = 0; i < 1; i++ ) {
The code below is what I am having problems with. Any help would be greatly appreciated.
import unlekker.util.*;

import unlekker.modelbuilder.*;

import ec.util.*;

import processing.opengl.*;

import peasy.*;

PeasyCam cam;

UGeometry cylinder;

void setup () {

size (800,800, OPENGL);

cam = new PeasyCam(this,100);

cam.setMinimumDistance(100);

cam.setMaximumDistance(500);



buildCylinder (16, 8.5, 6, 0, 0);

}

void draw () {

rotateX(-.5);

rotateY(-.5);

background(180);



drawCylinder();



}

void buildCylinder (int sides, float r, float h, float xOrgin, float yOrgin) {

float angle = TWO_PI/sides;

//Draw Bottom Shape

cylinder = new UGeometry();

cylinder.beginShape(TRIANGLE_FAN);

cylinder.vertex(0,0,-h/2);

for ( int i = 0; i < sides; i++ ) {

float x = ( cos ( angle * i ) * r ) + xOrgin;

float y = ( sin ( angle * i ) * r ) + yOrgin;

cylinder.vertex (x,y,-h/2);

}

cylinder.endShape();

print(cylinder.faceNum+"\n");



}

void drawCylinder(){

cylinder.draw(this);

//print(cylinder.faceNum+"\n");

cylinder.calcFaceNormals();

}

Flat Sided Circle Problem

[3 Replies]
- 07-Feb-2012 03:31 PM
- Forum: Programming Questions
I am trying to do a simple code to draw a multisided circle using the code below. For some reason, a flat side starts to form in my circle and I am not sure why. It is pretty obvious when the number of sides is 19.

Any thoughts?
1. void setup() {
2. int sides = 18;
3. size(800,800);
4. drawCylinder(400,400,sides,200);
5. }
6. void drawCylinder(int orginX, int orginY, int sides, float r) {
7. float angle = 360 / sides;
8. beginShape();
9. for(int i = 0; i < sides; i++) {
10. float x = (cos( radians ( i * angle ) ) * r)+ orginX;
11. float y = (sin( radians ( i * angle ) ) * r)+ orginY;
12. vertex( x,y );
13. print ("i: "+i+" "+x+","+y+"\n");
14. }
15. endShape(CLOSE);
16. }

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