// Blending shader

// PI constant
#define M_PI 3.1415926535897932384626433832795

// Used by lighting fragment shader
varying vec3 N;
varying vec3 v;

// Bending angle (-30 to 30 degrees)
uniform float bendAngle;

// Creates matrix representing rotation around X axis
mat4 makeXRotMat(float myAngle)
{
	// STUDENTS CODE //
	//                   X    Y    Z    W
	mat4 retMat = mat4( 1.0, 0.0, 0.0, 0.0,
						0.0, cos(myAngle), -sin(myAngle), 0.0,
						0.0, sin(myAngle), cos(myAngle), 0.0,
						0.0, 0.0, 0.0, 1.0 );

	// TODO: create matrix representing rotation around X axis
	// Hint: use circle equation in parametric form
	// X column should remain constant - YZ unit vectors represent desired change of base vectors

	// STUDENTS CODE END //
	return retMat;
}

// Vertex shader entry point
void main()
{
	// Copy vertex
	vec4 tmpV = gl_Vertex;
	
	// STUDENTS CODE //
	// TODO: Create blended cone animation using vertices with Z > 1.0

	// Step one: create rotation matrices: one should represent rotation and the other should be identity matrix
	// We will blend vertex rotation between them
	mat4 matOne = makeXRotMat(bendAngle);
	
	// Step two: calculate blending coefficient - we start bending if given vertex tmpV has Z coordinate greater than 1.0
	// Cone has height of 4.0 units (Z axis), so coefficient should be calculated for Z in range from 1.0 to 4.0 
	// and result should be between 0.0 and 1.0
	// Hint: use function clamp(val_to_clamp, min, max);
	// float coeff = ...
	float coeff = clamp((tmpV.z - 1)/3, 0, 1);

	// Step three: alter only vertices with Z coordinate greater than 1.0 
	// Hint: You can access tmpV like a structure - tmpV.x, tmpV.y, tmpV.z
	// Hint: tmpV must be translated to the origin in Z axis before transformation, since center of rotation will be in the origin
	// Hint: matrices can be blended using regular multiplication operations - blendedMat = coeffN1 * matN1 + coeffN2 * matN2 + ...
	// Hint: sum of coeffN1 + coeffN2 + ... must be equal to 1.0
	// Hint: after altering tmpV with blendMat (tmpV = tmpV * blendMat; or tmpV *= blendMat), remember to translate tmpV back in Z axis!
	
	if(tmpV.z > 1.0) {
		tmpV.z -= 1.0;		
		tmpV *= (coeff*matOne + (1f-coeff)*mat4(1f));
		tmpV.z += 1.0;
	}

	// STUDENTS CODE END //

	// tmpV now contains final position in model space..

	// Transforming The Vertex
	v = vec3(gl_ModelViewMatrix * tmpV);       
	N = normalize(gl_NormalMatrix * gl_Normal);
	gl_Position = gl_ModelViewProjectionMatrix * tmpV;
}