§ Иллюстрация

§ Код

1SCREEN 13
2
3TYPE vec3
4  x AS SINGLE
5  y AS SINGLE
6  z AS SINGLE
7END TYPE
8
9DIM cam AS vec3, ctr AS vec3, ctn AS vec3
10DIM lpt AS vec3, lno AS vec3, ltn AS vec3
11DIM nor AS vec3, dir AS vec3
12DIM ref AS vec3, pln AS vec3
13
14SetPal
15
16' Directional light
17dir.x = 2
18dir.y = 2
19dir.z = 0
20normvec3 dir
21
22' Landscape
23pln.y = -4
24
25' Center of sphere
26ctr.x = 0
27ctr.y = 0
28ctr.z = 16
29
30r = 3
31speed = 1 / 30
32
33WHILE 1
34
35  ' Light point
36  lpt.x = 8 * COS(move * speed)
37  lpt.y = 1
38  lpt.z = 9
39
40  ' Ball position
41  ctr.y = ABS(r * COS(move * speed)) + pln.y + r
42
43  FOR y = 100 TO -99 STEP -1
44  FOR x = -160 TO 160
45
46    sx = x + 160
47    sy = 100 - y
48
49    ' Init cam vector
50    cam.x = x / 200
51    cam.y = y / 200
52    cam.z = 1
53
54    ' Search sphere intersect
55    t = intersec(cam, ctr, r)
56
57    ' Found
58    IF t > 0 AND cam.y * t > pln.y THEN
59
60      ' Calculate normal and point of intersect
61      mul3vec cam, t        ' cam *= t
62      sub3vec nor, cam, ctr ' nor = cam - ctr
63      sub3vec lno, lpt, cam ' lno = lpt - cam
64      mul3vec cam, -1       ' cam = -cam
65
66      ' Normalize vectors
67      normvec3 nor
68      normvec3 cam
69      normvec3 lno
70
71      ' Reflect camera & normal
72      refl = 2 * mul3(cam, nor)
73      ref.x = refl * nor.x - cam.x
74      ref.y = refl * nor.y - cam.y
75      ref.z = refl * nor.z - cam.z
76      normvec3 ref
77
78      ' Directional and specular
79      ldir = mul3(nor, dir): IF ldir < 0 THEN ldir = 0
80      lspe = mul3(ref, lno): IF lspe < 0 THEN lspe = 0 ELSE lspe = lspe ^ 7
81
82      ' Total Light
83      lv = ldir * .8 + lspe * .5
84      IF lv < 0 THEN lv = 0
85      IF lv > 1 THEN lv = 1
86
87      PSET (sx, sy), lv * 63 + 64
88
89    ELSE
90
91      ' Only floor
92      IF y < 0 THEN
93
94        IF cam.y = 0 THEN cam.y = 1
95
96        ' Point of intersection of floor
97        pln.z = pln.y / cam.y
98        pln.x = cam.x * pln.z
99
100        u = INT(pln.x)
101        v = INT(pln.z)
102        c = ((v + move) XOR (u + 16)) AND 63
103
104        c = 16 * c / pln.z
105        IF c > 63 THEN c = 63
106
107        ' Search intersection of ball, light and floor
108        sub3vec ctn, ctr, pln
109        sub3vec ltn, lpt, pln
110
111        ' --------------------------------------
112        ' LTN = LPT (Light Pointer) - Plane(XYZ)
113        ' CTN = CTR (Center Sphere) - Plane(XYZ)
114        ' --------------------------------------
115
116        t = intersec(ltn, ctn, r)
117        IF t > 0 THEN c = c \ 2
118
119        PSET (sx, sy), 64 + c
120
121      ELSE
122
123        PSET (sx, sy), 0
124
125      END IF
126
127    END IF
128
129  NEXT
130  NEXT
131
132  ' I like'd moved moved!
133  move = move + 1
134
135WEND
136
137FUNCTION intersec (cam AS vec3, ctr AS vec3, r AS SINGLE)
138
139  a = mul3(cam, cam)
140  b = -mul3(cam, ctr) * 2
141  c = mul3(ctr, ctr) - r ^ 2
142  d = b ^ 2 - 4 * a * c
143  t = 0
144
145  IF d >= 0 THEN
146
147    d = SQR(d)
148    t1 = (-b - d) / (2 * a)
149    t2 = (-b + d) / (2 * a)
150
151    IF t1 < 0 AND t2 < 0 THEN t = -1
152    IF t1 < 0 AND t2 > 0 THEN t = t2
153    IF t1 > 0 AND t2 < 0 THEN t = t1
154    IF t1 > 0 AND t2 > 0 THEN
155      IF t1 < t2 THEN t = t1 ELSE t = t2
156    END IF
157
158  END IF
159
160  intersec = t
161
162END FUNCTION
163
164FUNCTION length (a AS vec3)
165  length = SQR(mul3(a, a))
166END FUNCTION
167
168FUNCTION mul3 (a AS vec3, b AS vec3)
169  mul3 = a.x * b.x + a.y * b.y + a.z * b.z
170END FUNCTION
171
172SUB mul3vec (v AS vec3, k AS SINGLE)
173  v.x = v.x * k
174  v.y = v.y * k
175  v.z = v.z * k
176END SUB
177
178SUB sub3vec (c AS vec3, a AS vec3, b AS vec3)
179  c.x = a.x - b.x
180  c.y = a.y - b.y
181  c.z = a.z - b.z
182END SUB
183
184SUB normvec3 (v AS vec3)
185  mul3vec v, 1 / length(v)
186END SUB
187
188SUB SetPal
189FOR i = 0 TO 63
190  OUT 968, i + 64
191  OUT 969, i
192  OUT 969, i
193  OUT 969, i
194NEXT
195END SUB