uniform float strength;
uniform vec4 coronaDir;
uniform vec4 view_direction;
uniform sampler2D GlowTex;
uniform float coronaExp;
uniform vec4 lightColor;
uniform float constAtt;
uniform float sqrAtt;
 
// input variables from Vertex Program.
varying vec2 vTexCoord;
 
float saturate( float inValue)
{
   return clamp( inValue, 0.0, 1.0);
}
 
void main(void)
{
   
   vec4 corona  = texture2D(GlowTex, vTexCoord);
   // view directoin is set up for the handedness, we need to flip it for ogl.
   vec3 vdir    = vec3(view_direction.x, view_direction.y, view_direction.z);
   vec3 cdir    = vec3(coronaDir.x, coronaDir.y, coronaDir.z);
 
   // Glow depending on cosine (dotprod) with "corona directon"
   float glow   = saturate(dot(vdir, cdir));
 
   gl_FragColor = strength * pow(glow, coronaExp) * corona * lightColor;  
}

uniform vec4 pos0;         // location of screen aligned quad
uniform float coronaSize;  // size of screen aligned quad (currently 16.0)
 
// output variables for Fragment Program.
varying vec2 vTexCoord;
 
void main(void)
{
       
   // Grab X and Y eye-space vectors in world-space ...
   
   // NOTE: OpenGL stores matrixes as column major, DirectX stores then row major.
   //       So here, we need to extract the rows we need...the D3D version of this
   //       shader is a touch simplier.
   vec3 dirX = vec3(
                    gl_ModelViewMatrix[0][0],
                    gl_ModelViewMatrix[1][0],
                    gl_ModelViewMatrix[2][0]
                   );
   vec3 dirY = vec3(
                    gl_ModelViewMatrix[0][1],
                    gl_ModelViewMatrix[1][1],
                    gl_ModelViewMatrix[2][1]
                   );
 
   // ... which are used for billboarding
   vec3 pos    = vec3(pos0) + coronaSize * (gl_Vertex.x * dirX + gl_Vertex.y * dirY );
   
   gl_Position = gl_ModelViewProjectionMatrix * vec4(pos,1.0);
   
   vTexCoord   = 0.5 * gl_Vertex.xy + 0.5;
 
   
}

class MyShaderCallBack : public video::IShaderConstantSetCallBack
{
	public :


		MyShaderCallBack ( IrrlichtDevice* _device )
		{
			device = _device;
		}


        virtual void OnSetConstants ( video::IMaterialRendererServices* services , s32 userData )
        {

                video::IVideoDriver* driver = services->getVideoDriver();

                float st = 20;
                services->setVertexShaderConstant("strength", (const float*)&st, 1);

                float st1 = 4;
                services->setVertexShaderConstant("coronaSize", (const float*)&st1, 1);

                // Set camera position
                core::vector3df pos = core::vector3df (-1,0,0);
                services->setVertexShaderConstant ( "coronaDir" , reinterpret_cast<f32*>( &pos ) , 3 );


                // Set camera position
                core::vector3df pos1 = device->getSceneManager()->getActiveCamera()->getPosition();
                services->setVertexShaderConstant ( "view_direction" , reinterpret_cast<f32*>( &pos1 ) , 3 );


                float st2 = 2;
                services->setVertexShaderConstant("coronaExp", (const float*)&st2, 1);


                float st3 = 1;
                services->setVertexShaderConstant("constAtt", (const float*)&st3, 1);

                float st4 = 1;
                services->setVertexShaderConstant("sqrAtt", (const float*)&st4, 1);

                // Set light color
                video::SColorf col(0.0f,255,255,0.0f);
                services->setVertexShaderConstant("lightColor", reinterpret_cast<f32*>(&col), 4);

                //Set pos to glow
                core::vector3df pos11 = core::vector3df (0,0,0);
                services->setVertexShaderConstant ( "pos0" , reinterpret_cast<f32*>( &pos11 ) , 3 );

				// set textures
			    int a = 0;services->setPixelShaderConstant("GlowTex", (f32 *)(&a), 0);
        }

	private :

		IrrlichtDevice* device;
};