/* Here is some relevant information regarding my rendering code:

Functions:
		
	- DrawShadowPlane1(): draws the floor plane
	- DrawShadowPlane2(): draws the wall plane
	- DrawShadowedObjects(): draws the object/s that will cast shadows

Planes:

	- Plane plane1;    (a = 0, b = 1, c = 0, d = 0)  --> this is the floor plane
	- Plane plane2;    (a = 1, b = 0, c = 0, d = 20) --> this is the wall plane
			
Projection matrices:

	- float projectionMatrix1[16];
	- float projectionMatrix2[16];

And I have a single point light source:

	- float lightPos[4] = { ... };
*/

////////////////////////////////////////////////////////////////

    // Firstly, I create the projection matrices:

    // Create the first projection matrix (for projection onto the floor plane)
    Vector3 normal = plane.GetNormal();
    float distance = plane.GetDistance();

    float dot = (lightPos[0] * normal.x) + (lightPos[1] * normal.y) + (lightPos[2] * normal.z) + (lightPos[3] * distance);

    projectionMatrix[0] = dot - lightPos[0] * normal.x;
    projectionMatrix[1] = -lightPos[1] * normal.x;
    projectionMatrix[2] = -lightPos[2] * normal.x;
    projectionMatrix[3] = -lightPos[3] * normal.x;

    projectionMatrix[4] = -lightPos[0] * normal.y;
    projectionMatrix[5] = dot -lightPos[1] * normal.y;
    projectionMatrix[6] = -lightPos[2] * normal.y;
    projectionMatrix[7] = -lightPos[3] * normal.y;

    projectionMatrix[8] = -lightPos[0] * normal.z;
    projectionMatrix[9] = -lightPos[1] * normal.z;
    projectionMatrix[10] = dot -lightPos[2] * normal.z;
    projectionMatrix[11] = -lightPos[3] * normal.z;

    projectionMatrix[12] = -lightPos[0] * distance; 
    projectionMatrix[13] = -lightPos[1] * distance;
    projectionMatrix[14] = -lightPos[2] * distance; 
  
    // Create the second projection matrix (for projection onto the wall plane)
    normal = plane2.GetNormal();
    distance = plane2.GetDistance();

	dot = (lightPos[0] * normal.x) + (lightPos[1] * normal.y) + (lightPos[2] * normal.z) + (lightPos[3] * distance);

    projectionMatrix2[0] = dot - lightPos[0] * normal.x;
    projectionMatrix2[1] = -lightPos[1] * normal.x;
    projectionMatrix2[2] = -lightPos[2] * normal.x;
    projectionMatrix2[3] = -lightPos[3] * normal.x;

    projectionMatrix2[4] = -lightPos[0] * normal.y;
    projectionMatrix2[5] = dot -lightPos[1] * normal.y;
    projectionMatrix2[6] = -lightPos[2] * normal.y;
    projectionMatrix2[7] = -lightPos[3] * normal.y;

    projectionMatrix2[8] = -lightPos[0] * normal.z;
    projectionMatrix2[9] = -lightPos[1] * normal.z;
    projectionMatrix2[10] = dot -lightPos[2] * normal.z;
    projectionMatrix2[11] = -lightPos[3] * normal.z;

    projectionMatrix2[12] = -lightPos[0] * distance; 
    projectionMatrix2[13] = -lightPos[1] * distance;
    projectionMatrix2[14] = -lightPos[2] * distance; 
    projectionMatrix2[15] = dot -lightPos[3] * distance;


    // DRAW SHADOW 1 ///////////////////////////////////////////////

    // Draw the plane that the shadow will project onto
    DrawShadowPlane1();

    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
    glDepthMask(GL_FALSE);
    glEnable(GL_STENCIL_TEST);
    
    // Draw the shadow plane into the stencil buffer
    glStencilFunc(GL_ALWAYS, 1, 0xFFFFFFFF);
    glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
    DrawShadowPlane1();
    
    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    glDepthMask(GL_TRUE);
    
    // Restrict drawing to the shadow plane
    glStencilFunc(GL_EQUAL, 1, 0xFFFFFFFF);
    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

    // Draw the shadow (blended with the shadow plane)
    // The depth buffer is disabled to prevent z-fighting
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);
    glColor4f(0.0f, 0.0f, 0.0f, 0.5f);
    glPushMatrix();
	    glMultMatrixf(projectionMatrix1);
	    DrawShadowedObjects();
    glPopMatrix();
    glDisable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_STENCIL_TEST);

    // DRAW SHADOW 2 ///////////////////////////////////////////////

    // Draw the plane that the shadow will project onto
    DrawShadowPlane2();

    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
    glDepthMask(GL_FALSE);
    glEnable(GL_STENCIL_TEST);
	
    // Draw the shadow plane into the stencil buffer
    glStencilFunc(GL_ALWAYS, 1, 0xFFFFFFFF);
    glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
    DrawShadowPlane2();
	
    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    glDepthMask(GL_TRUE);
	
    // Restrict drawing to the shadow plane
    glStencilFunc(GL_EQUAL, 1, 0xFFFFFFFF);
    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

    // Draw the shadow (blended with the shadow plane)
    // The depth buffer is disabled to prevent z-fighting
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);
    glColor4f(0.0f, 0.0f, 0.0f, 0.5f);
    glPushMatrix();
	    glMultMatrixf(projectionMatrix2);
	    DrawShadowedObjects();
    glPopMatrix();
    glDisable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_STENCIL_TEST);


    ////////////////////////////////////////////////////////////////

    // And lastly I draw the objects that cast the shadows
    glColor3f(1.0f, 1.0f, 1.0f);
    DrawShadowedObjects();