1. // Blending shader
2.  
3. // PI constant
4. #define M_PI 3.1415926535897932384626433832795
5.  
6. // Used by lighting fragment shader
7. varying vec3 N;
8. varying vec3 v;
9.  
10. // Bending angle (-30 to 30 degrees)
11. uniform float bendAngle;
12.  
13. // Creates matrix representing rotation around X axis
14. mat4 makeXRotMat(float myAngle)
15. {
16.         // STUDENTS CODE //
17.         //                   X    Y    Z    W
18.         mat4 retMat = mat4( 1.0, 0.0, 0.0, 0.0,
19.                                                 0.0, cos(myAngle), -sin(myAngle), 0.0,
20.                                                 0.0, sin(myAngle), cos(myAngle), 0.0,
21.                                                 0.0, 0.0, 0.0, 1.0 );
22.  
23.         // TODO: create matrix representing rotation around X axis
24.         // Hint: use circle equation in parametric form
25.         // X column should remain constant - YZ unit vectors represent desired change of base vectors
26.  
27.         // STUDENTS CODE END //
28.         return retMat;
29. }
30.  
31. // Vertex shader entry point
32. void main()
33. {
34.         // Copy vertex
35.         vec4 tmpV = gl_Vertex;
36.        
37.         // STUDENTS CODE //
38.         // TODO: Create blended cone animation using vertices with Z > 1.0
39.  
40.         // Step one: create rotation matrices: one should represent rotation and the other should be identity matrix
41.         // We will blend vertex rotation between them
42.         mat4 matOne = makeXRotMat(bendAngle);
43.        
44.         // Step two: calculate blending coefficient - we start bending if given vertex tmpV has Z coordinate greater than 1.0
45.         // Cone has height of 4.0 units (Z axis), so coefficient should be calculated for Z in range from 1.0 to 4.0
46.         // and result should be between 0.0 and 1.0
47.         // Hint: use function clamp(val_to_clamp, min, max);
48.         // float coeff = ...
49.         float coeff = clamp((tmpV.z - 1)/3, 0, 1);
50.  
51.         // Step three: alter only vertices with Z coordinate greater than 1.0
52.         // Hint: You can access tmpV like a structure - tmpV.x, tmpV.y, tmpV.z
53.         // Hint: tmpV must be translated to the origin in Z axis before transformation, since center of rotation will be in the origin
54.         // Hint: matrices can be blended using regular multiplication operations - blendedMat = coeffN1 * matN1 + coeffN2 * matN2 + ...
55.         // Hint: sum of coeffN1 + coeffN2 + ... must be equal to 1.0
56.         // Hint: after altering tmpV with blendMat (tmpV = tmpV * blendMat; or tmpV *= blendMat), remember to translate tmpV back in Z axis!
57.        
58.         if(tmpV.z > 1.0) {
59.                 tmpV.z -= 1.0;         
60.                 tmpV *= (coeff*matOne + (1f-coeff)*mat4(1f));
61.                 tmpV.z += 1.0;
62.         }
63.  
64.         // STUDENTS CODE END //
65.  
66.         // tmpV now contains final position in model space..
67.  
68.         // Transforming The Vertex
69.         v = vec3(gl_ModelViewMatrix * tmpV);      
70.         N = normalize(gl_NormalMatrix * gl_Normal);
71.         gl_Position = gl_ModelViewProjectionMatrix * tmpV;
72. }