frag_shader.frag

uniform sampler2D texture;
uniform vec2 resolution;
uniform vec2 mouse;
uniform vec2 time;

// The RGB values are the ambient light color
// and the alpha is the ambient intensity
uniform vec4 ambientData;
// The RGB values are the light color
// and the alpha is the light intensity
uniform vec4 lightData;
// Maximum radius of the light
uniform vec2 lightSize;

void main() {
  // Light's position
  vec2 position = mouse/resolution.xx;

  // Makes the light change its size slightly to make a fire effect
  float maxDistance = lightSize + 0.015*sin(time.x);
  // Gets the distance from the light's position and the fragment coord
  float distance = distance(gl_FragCoord.xy/resolution.xx, position);
  // Calculates the amount of light for the fragment
  float value = 1.0 - smoothstep(-0.2, maxDistance, distance);

  // Gets the original color from the texture
  vec4 pixel = texture2D(texture, gl_TexCoord[0].xy);

  // Applies the ambient light to the original pixel color
  vec3 ambient = pixel.rgb * ambientData.rgb * ambientData.a;

  // Calculates the light color for the pixel
  vec3 light = lightData.rgb * lightData.a * clamp(value, 0.0, 1.0);

  // Applies the light to the pixel
  vec3 intensity = ambient + light;
  vec3 final = pixel.rgb * intensity;

  gl_FragColor = vec4(final, 1.0);
}