SimpleFragmentShader.fragmentshader

#version 330 core

// Interpolated values from the vertex shaders
in vec2 UV;
in vec3 Position_worldspace;
in vec3 Normal_cameraspace;
in vec3 EyeDirection_cameraspace;
in vec3 LightDirection1_cameraspace;
in vec3 LightDirection2_cameraspace;
in vec3 LightDirection3_cameraspace;
in vec3 LightDirection4_cameraspace;

// Ouput data
layout(location = 0) out vec3 color;

// Values that stay constant for the whole mesh.
uniform sampler2D myTextureSampler;
uniform mat4 MV;
uniform vec3 LightPosition1_worldspace;
uniform vec3 LightPosition2_worldspace;
uniform vec3 LightPosition3_worldspace;
uniform vec3 LightPosition4_worldspace;
uniform float LightPower1;
uniform float LightPower2;
uniform float LightPower3;
uniform float LightPower4;

void main(){

	// Light emission properties
	// You probably want to put them as uniforms
	vec3 LightColor = vec3(1, 1, 1);
	
	// Material properties
	vec3 MaterialDiffuseColor = vec3(0, 1, 0);
	vec3 MaterialAmbientColor = vec3(0.3, 0.3, 0.3) * MaterialDiffuseColor;

	// Distance to the light
	float distance1 = length(LightPosition1_worldspace - Position_worldspace);

	// Normal of the computed fragment, in camera space
	vec3 n1 = normalize(Normal_cameraspace);
	// Direction of the light (from the fragment to the light)
	vec3 l1 = normalize(LightDirection1_cameraspace);
	// Cosine of the angle between the normal and the light direction, 
	// clamped above 0
	//  - light is at the vertical of the triangle -> 1
	//  - light is perpendiular to the triangle -> 0
	//  - light is behind the triangle -> 0
	float cosTheta1 = clamp(dot(n1, l1), 0, 1);
	
	float distance2 = length(LightPosition2_worldspace - Position_worldspace);
	vec3 n2 = normalize(Normal_cameraspace);
	vec3 l2 = normalize(LightDirection2_cameraspace);
	float cosTheta2 = clamp(dot(n2, l2), 0, 1);
	
	float distance3 = length(LightPosition3_worldspace - Position_worldspace);
	vec3 n3 = normalize(Normal_cameraspace);
	vec3 l3 = normalize(LightDirection3_cameraspace);
	float cosTheta3 = clamp(dot(n3, l3), 0, 1);
	
	float distance4 = length(LightPosition4_worldspace - Position_worldspace);
	vec3 n4 = normalize(Normal_cameraspace);
	vec3 l4 = normalize(LightDirection4_cameraspace);
	float cosTheta4 = clamp(dot(n4, l4), 0, 1);
	
	color = 
		// Ambient : simulates indirect lighting
		MaterialAmbientColor
		// Diffuse : "color" of the object
		+ MaterialDiffuseColor * LightColor * LightPower1 * cosTheta1 / (distance1*distance1)
                + MaterialDiffuseColor * LightColor * LightPower2 * cosTheta2 / (distance2*distance2)
                + MaterialDiffuseColor * LightColor * LightPower3 * cosTheta3 / (distance3*distance3)
                + MaterialDiffuseColor * LightColor * LightPower4 * cosTheta4 / (distance4*distance4);

}