drawing more than one of my glowing lights makes them share the light, cant split them - glsl

Question

I am trying to create two independent glowing lights but when a make the second share the light stretches between the 2
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
// Normalized pixel coordinates (from 0 to 1)
vec2 uv = fragCoord/iResolution.xy;
uv =(fragCoord-.5*iResolution.xy)/iResolution.y;
vec3 col = vec3(0.);
float radius = 0.5;
float glowSpeed = 1.;
vec2 glowPos = vec2(uv.x, uv.y+0.5);
vec2 glowPos2 = vec2(uv.x+0.5, uv.y+0.0);
float glowCol1 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv+glowPos);
float glowCol2 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv+glowPos2);
col += vec3(glowCol1, glowCol1, 0.);
col += vec3(glowCol2, glowCol2, 0.);
// Output to screen
fragColor = vec4(col, 1);
}
enter image description here

Answer 1

uv is a position relative to the fragment currently being processed. So the position of a light source must not depend on uv. e.g.:
vec2 glowPos = vec2(0.5, 0.5);
vec2 glowPos2 = vec2(-0.5, -0.5);
The distance between 2 points is the length of the vector from one point to the other. A vector between 2 points is calculated by subtracting one point from the other, but not by calculating the sum:
float glowCol1 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv-glowPos);
float glowCol2 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv-glowPos2);
The result for glowCol1 and glowCol2 can become negative. Thus, one light source would negatively affect the other. You must clamp the result in the range [0, 1]:
glowCol1 = clamp(glowCol1, 0.0, 1.0);
glowCol2 = clamp(glowCol2, 0.0, 1.0);
Complete and working shader:
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
// Normalized pixel coordinates (from 0 to 1)
vec2 uv = fragCoord/iResolution.xy;
uv = uv * 2.0 - 1.0;
uv.x *= iResolution.x / iResolution.y;
vec3 col = vec3(0.);
float radius = 0.5;
float glowSpeed = 1.;
vec2 glowPos = vec2(0.5, 0.5);
vec2 glowPos2 = vec2(-0.5, -0.5);
float glowCol1 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv-glowPos);
float glowCol2 = radius * (cos(glowSpeed * iTime) + 6.) / 7. - length(uv-glowPos2);
glowCol1 = clamp(glowCol1, 0.0, 1.0);
glowCol2 = clamp(glowCol2, 0.0, 1.0);
col += vec3(glowCol1, glowCol1, 0.);
col += vec3(glowCol2, glowCol2, 0.);
// Output to screen
fragColor = vec4(col, 1);
}