I would like to connect the points from the red path, to the y-axis in blue. I figured out that the problem with my triangles came from the first point (V0) : it is not located where it should be.

In the console, it says its location is at 0,0, but in the emulator, it is not.

The code :

for(int i = 1; i < 2; i++) {   
        CCLOG(@"_polyVertices[i-1].x : %f, _polyVertices[i-1].y : %f", _polyVertices[i-1].x, _polyVertices[i-1].y);
        CCLOG(@"_polyVertices[i].x : %f, _polyVertices[i].y : %f", _polyVertices[i].x, _polyVertices[i].y);
        ccDrawLine(_polyVertices[i-1], _polyVertices[i]);
    } 

The output :

_polyVertices[i-1].x : 0.000000, _polyVertices[i-1].y : 0.000000
_polyVertices[i].x : 50.000000, _polyVertices[i].y : 0.000000

And the result : (the layer goes up, i could not take the screenshot before the layer started to go up, but the first red point starts at y=0) :

Then it creates an unwanted triangle when the code continues :

Would you have any idea about this? (So to force the first blue point to start at 0,0, and not at 50,0 as it seems to be now)

Here is the code :

- (void)generatePath{
    float x = 50; //first red point
    float y = 0;
    for(int i = 0; i < kMaxKeyPoints+1; i++) {
        if (i<3){
            _hillKeyPoints[i] = CGPointMake(x, y);
            x = 150 + (random() % (int) 30);
            y += -40;
        } else if(i<20){ //going right
            _hillKeyPoints[i] = CGPointMake(x, y);
            x += (random() % (int) 30);
            y += -40;
        } else if(i<25){ //stabilize
            _hillKeyPoints[i] = CGPointMake(x, y);
            x = 150 + (random() % (int) 30);
            y += -40;
        } else if(i<30){ //going left
            _hillKeyPoints[i] = CGPointMake(x, y);
            //x -= (random() % (int) 10);
            x = 150 + (random() % (int) 30);
            y += -40;
        } else { //back to normal
            _hillKeyPoints[i] = CGPointMake(x, y);
            x = 150 + (random() % (int) 30);
            y += -40;
        }
    }
}

-(void)generatePolygons{
    static int prevFromKeyPointI = -1;
    static int prevToKeyPointI = -1;

    // key points interval for drawing
    while (_hillKeyPoints[_fromKeyPointI].y > -_offsetY+winSizeTop) {
        _fromKeyPointI++;
    }
    while (_hillKeyPoints[_toKeyPointI].y > -_offsetY-winSizeBottom) {
        _toKeyPointI++;
    }

    if (prevFromKeyPointI != _fromKeyPointI || prevToKeyPointI != _toKeyPointI) {

        _nPolyVertices = 0;
        float x1 = 0;
        int keyPoints = _fromKeyPointI;

    for (int i=_fromKeyPointI; i<_toKeyPointI; i++){

        //V0: at (0,0)
        _polyVertices[_nPolyVertices] = CGPointMake(x1, y1); //first blue point
        _polyTexCoords[_nPolyVertices++] = CGPointMake(x1, y1);

        //V1: to the first "point"
        _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y);
        _polyTexCoords[_nPolyVertices++] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y);

        keyPoints++; //from point at index 0 to 1
        //V2, same y as point n°2:
        _polyVertices[_nPolyVertices] = CGPointMake(0, _hillKeyPoints[keyPoints].y);  
        _polyTexCoords[_nPolyVertices++] = CGPointMake(0, _hillKeyPoints[keyPoints].y);


        //V1 again
        _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2];
        _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2];

        //V2 again
        _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2];
        _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2];
        //CCLOG(@"_nPolyVertices V2 again : %i", _nPolyVertices);

        //V3 = same x,y as point at index 1
        _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y);
        _polyTexCoords[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y);


        y1 = _polyVertices[_nPolyVertices].y;
        _nPolyVertices++;
    }

        prevFromKeyPointI = _fromKeyPointI;
        prevToKeyPointI = _toKeyPointI; 
    }
}

- (void) draw {
    //RED
    glColor4f(1, 1, 1, 1);
    for(int i = MAX(_fromKeyPointI, 1); i <= _toKeyPointI; ++i) {
        glColor4f(1.0, 0, 0, 1.0); 
        ccDrawLine(_hillKeyPoints[i-1], _hillKeyPoints[i]);        
    }

    //BLUE
    glColor4f(0, 0, 1, 1);
    for(int i = 1; i < 2; i++) {   
        CCLOG(@"_polyVertices[i-1].x : %f, _polyVertices[i-1].y : %f", _polyVertices[i-1].x, _polyVertices[i-1].y);
        CCLOG(@"_polyVertices[i].x : %f, _polyVertices[i].y : %f", _polyVertices[i].x, _polyVertices[i].y);
        ccDrawLine(_polyVertices[i-1], _polyVertices[i]);
    } 

}

Thanks