Draw a white line in opengl es

Question

I have an image. Over it I draw a semi transparent polygon. Over the semi transparent polygon I draw a line.

I cannot seem to get this line to be white. It is almost as though it is blending with the image or polygon.

 glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
 glDrawArrays(GL_LINE_LOOP, 0, area.polygonShapeData.totalPoints);

What could I be doing to make this line not be white? It comes out a darker gray.

Answer 1

Perhaps you've got blending enabled in something like GL_DST_ALPHA, GL_ONE_MINUS_DST_ALPHA mode? Try glDisable(GL_BLEND) and see if you get better results.

Answer 2

Do you use anti-aliasing? I've noticed hair thin lines coming out faded if GL_LINE_SMOOTH is enabled. Also try increasing the width with glLineWidth.