Multi textures and multi lights in OpenGL 3.3 - c++

Question

I have a project of castle and i send one light and one material to shaders. I want to add one more light and texture, but i don't know how to do it in shaders.
This is my fragment shader:
#version 130
out vec4 pixelColor;
in vec4 l;
in vec4 n;
in vec4 v;
uniform sampler2D textureMap0, textureMap1;
in vec2 iTexCoord;
in vec2 iTexCoord2;
uniform vec4 dragi1;
uniform vec4 dragi2;
uniform vec4 dragi3;
uniform float polysk;
uniform vec4 Light0ambient;
uniform vec4 Light0diffuse;
uniform vec4 Light0specular;
uniform vec4 Light0position;
uniform vec4 Material0emission;
uniform vec4 Material0ambient;
uniform vec4 Material0diffuse;
uniform vec4 Material0specular;
uniform float Material0shininess;
void main(void) {
vec4 ml=normalize(l);
vec4 mn=normalize(n);
vec4 mv=normalize(v);
vec4 mr=reflect(-ml,mn);
float nl=max(dot(ml,mn),0);
float rv=pow(max(dot(mr,mv),0),Material0shininess);
pixelColor=Light0ambient*Material0ambient+Light0diffuse*Md*vec4(nl,nl,nl,1)+Light0specular*Material0specular*vec4(rv,rv,rv,0);
}
And this is my vertex shader:
#version 130
uniform mat4 P;
uniform mat4 V;
uniform mat4 M;
in vec4 vertex;
in vec4 normal;
in vec2 texCoord;
out vec4 l;
out vec4 n;
out vec4 v;
out vec2 iTexCoord;
out vec2 iTexCoord2;
uniform vec4 Light0position;
void main(void) {
gl_Position=P*V*M*vertex;
l=normalize(V*(Light0position-M*vertex));
n=normalize(V*M*normal);
v=normalize(vec4(0,0,0,1)-V*M*vertex);
iTexCoord = texCoord;
iTexCoord2 = (n.xy + 1)/2;
}
It is simple to do?
And one more question, how to create a spotlight? Can i do this in simple way?

Answer 1

When you want to use multiple lights in your shaders you generally store all your light and material data in arrays and process each of those in one large for-loop with or without GLSL functions.
For example, you could create a light and a material struct and create a uniform array of those structs like this:
struct Light {
vec4 position;
vec4 ambient;
vec4 diffuse;
vec4 specular;
};
struct Material {
vec4 ambient;
vec4 diffuse;
vec4 specular;
vec4 emission;
float shininess;
};
uniform Light lights[4]; // Use 4 lights
uniform Material materials[2]; // Use 2 materials
Then the structure of your fragment shader could look something like this:
out vec4 color;
void main()
{
// define an output color value
vec3 output;
// calculate lighting value per light source
for(int i = 0; i < 4; i++)
outout += someFunctionToCalculateLight(lights[i], materials[0]);
color = vec4(output, 1.0);
}
In this case a function was created to calculate the resulting lighting color per light source and added to the final output color. This is generally how you work with multiple lights. Note that this is a very basic example.
Also, if you want to know how to create a spotlight, you're better off following tutorials on that subject of which there are plenty to be found online instead of asking that around here.
A few tutorials:
http://www.mbsoftworks.sk/index.php?page=tutorials&series=1&tutorial=20
http://www.lighthouse3d.com/tutorials/glsl-core-tutorial/spotlights/
http://www.learnopengl.com/#!Lighting/Light-casters