1. Compute the colour at point G – Guraud Shading
(-1, 1)
(1, 1) A B F E
y = 0
G=(-1, 0) D C
(-2, -1)
(2, -1)
RGB Colours:
CA = (100, 200, 100)
CB = (50, 100, 200)
CC= (100, 100, 200)
CD = (200, 100, 50)

2. Compute the colour at point G – Guraud Shading
I(t)
I(0) t
Line AD
x = -1 –t
y = 1 –2t
y=0 -> t = ½ -> x = -1.5
E = (0, -1.5)
Linear interpolate the colours
I = I(0) + (I(1) – I(0))t
I(1/2) = (I(0) + I(1))/2
Colour at point E
CE = (CA + CD)/2 = (150, 150, 75)

3. Compute the colour at point G – Guraud Shading
I(t)
I(0) t
Line BC
x = 1 +t
y = 1 –2t
y=0 -> t = ½ -> x = 1.5
E = (0, 1.5)
Linear interpolate the colours
I = I(0) + (I(1) – I(0))t
I(1/2) = (I(0) + I(1))/2
Colour at point F
CE = (CB + CC)/2 = (75, 100, 200)

4. Compute the colour at point G – Guraud Shading
I(t)
I(0) t
Line EF
x = t
y = 0
X=-1 -> t = 1/6
Linear interpolate the colours
I = I(0) + (I(1) – I(0))t
I(1/6) = I(0)+(I(1)-I(0))/6
Colour at point G
CE = (5CE + CF)/6 = (138, 142,96)

5. Compute the normal vector at point G – Phong shading
(-1, 1)
(1, 1) A B F E
y = 0
G=(-1, 0) D C
(-2, -1)
(2, -1)
Normal Vectors
NA = (1, 2, 3)
NB = (1, 0, 4)
NC= (0, 1, 2)
ND = (2, 1, 3)

6. Compute the normal vector at point G – Phong shading
NG = (5NE+NF)/6
= (1.56, 1.56, 3)
NE = (NA + ND)/2
= (1.5, 1.5, 3)
NF = (NB + NC)/2
= (0.5, 0.5, 3)