I would like to help you a bit;
here is a little circle code ;
void main()
{
vec2 uv = vTex;
uv.y =1.-uv.y; // flip uv screen ;
vec2 cpos=vec2(0.0,0.0); /// position of our circle
float distance = distance(cpos, uv);
if (distance > 0.05)
gl_FragColor = vec4(0, 0, 0, 1.0);
else
gl_FragColor = vec4(1, 1, 1, 1.0);
}
[/code:1psl8odz]
The position of vectors change depending of the screen if it's flipped or not;
if you comment : uv.y =1.-uv.y; the bottom left is (0,0) if not flipped
the top left is (0,0).. try to change the position of circle : vec2 cpos = vec2(0.2,0.2) ... etc
when flip is used it's not flip texture but it's flip the screen , and the reason of inversed vectors are here .
Hope this help