From 6d21cde397ff246c053274c47fd33f3b84f68c6e Mon Sep 17 00:00:00 2001
From: talha <talha@talhaamir.xyz>
Date: Wed, 27 Mar 2024 04:19:47 +0500
Subject: Added directional lighting, point lights

---
 source/shaders/light_subject.fs.glsl | 58 +++++++++++++++++++++++++++++++-----
 1 file changed, 50 insertions(+), 8 deletions(-)

(limited to 'source/shaders/light_subject.fs.glsl')

diff --git a/source/shaders/light_subject.fs.glsl b/source/shaders/light_subject.fs.glsl
index 54bf700..aa3cf36 100644
--- a/source/shaders/light_subject.fs.glsl
+++ b/source/shaders/light_subject.fs.glsl
@@ -1,45 +1,87 @@
 #version 330 core
+
 struct Material {
+  sampler2D diffuse;
+  sampler2D specular;
+  float shininess;
+};
+
+struct Light {
   vec3 ambient;
   vec3 diffuse;
   vec3 specular;
-  float shininess;
+
+  vec3 position;
 };
 
-struct Light {
+struct DirectionalLight {
+  vec3 direction;
+
   vec3 ambient;
   vec3 diffuse;
   vec3 specular;
+};
 
+struct PointLight {
   vec3 position;
+
+  vec3 ambient;
+  vec3 diffuse;
+  vec3 specular;
+
+  // attentuation factors
+  float kC;
+  float kL;
+  float kQ;
 };
 
+in vec2 texCoords;
 in vec3 fragNormal;
 in vec3 worldPosition;
 
 uniform Material  material;
 uniform Light     light;
+uniform DirectionalLight dirLight;
+uniform PointLight pointLight;
 uniform vec3			cameraPosition;
 uniform vec3      lightColor;
-uniform sampler2D smilingTexture;
-uniform sampler2D containerTexture;
 
 out vec4 FragColor;
 
 void main() {
-		 vec3 ambientLight = light.ambient * material.ambient;
+     float lightDistance = length(pointLight.position - worldPosition);
+     float attenuationFactor = 1.0 / 
+     (pointLight.kC + (pointLight.kL * lightDistance) + (pointLight.kQ * lightDistance * lightDistance));
+
+		 vec3 ambientLight = attenuationFactor * pointLight.ambient * vec3(texture(material.diffuse, texCoords));
 
 //	 @note: Diffuse calculations
-     vec3 lightDir = normalize(light.position - worldPosition);
+     //vec3 lightDir = normalize(light.position - worldPosition);
+     /*
+     @note: an explanation of why the light direction vector is taken from fragment to the 
+     light source.
+     Basic LA really, we need to calculate the angle between the direction of the 2 vectors:
+      a. The direction at which light incidents with the fragment
+      b. The normal vector
+     The reason the light direction is taken from the fragment to the light source, is precisely so we can calculate
+     the angle between the normal and the direction at which light would hit. This if taken as starting from the light
+     source would actually be incorrect, since we would be calculating the angle between the light source in the direction
+     of the fragment and the normal. Consider what happens when it is directly above. The angle becomes 180, not 0. This 
+     is because the normal moves in the direction opposite to the lights direction if taken this way, which is not what
+     we expect or want.
+     Reversing this, allows us to consider the angle at the point in which light hits the fragment, and the normal vector
+     of the fragment. 
+     */
+     vec3 lightDir = normalize(pointLight.position - worldPosition);
      float diffuseStrength = max(dot(lightDir, fragNormal), 0.0);
-     vec3 diffuseLight = light.diffuse * (diffuseStrength * material.diffuse);
+     vec3 diffuseLight = attenuationFactor * pointLight.diffuse * diffuseStrength * vec3(texture(material.diffuse, texCoords));
 
 //	 @note: Specular calculations
 		 vec3  viewDir		      = normalize(cameraPosition - worldPosition);
 		 vec3  reflectDir				= reflect(-lightDir, fragNormal);
 		 float specularity			= max(dot(viewDir, reflectDir), 0.0);
 		 float shinePower				= pow(specularity, material.shininess);
-		 vec3  specularLight		= light.specular * (shinePower * material.specular);
+		 vec3  specularLight		= attenuationFactor * pointLight.specular * shinePower * vec3(texture(material.specular, texCoords));
 
      vec3 color = ambientLight + diffuseLight + specularLight;
      FragColor = vec4(color, 1.0);
-- 
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