§ Программный код
SCREEN 13
TYPE vec3
x AS SINGLE
y AS SINGLE
z AS SINGLE
END TYPE
DIM cam AS vec3, ctr AS vec3, ctn AS vec3
DIM lpt AS vec3, lno AS vec3, ltn AS vec3
DIM nor AS vec3, dir AS vec3
DIM ref AS vec3, pln AS vec3
SetPal
' Directional light
dir.x = 2
dir.y = 2
dir.z = 0
normvec3 dir
' Landscape
pln.y = -4
' Center of sphere
ctr.x = 0
ctr.y = 0
ctr.z = 16
r = 3
speed = 1 / 30
WHILE 1
' Light point
lpt.x = 8 * COS(move * speed)
lpt.y = 1
lpt.z = 9
' Ball position
ctr.y = ABS(r * COS(move * speed)) + pln.y + r
FOR y = 100 TO -99 STEP -1
FOR x = -160 TO 160
sx = x + 160
sy = 100 - y
' Init cam vector
cam.x = x / 200
cam.y = y / 200
cam.z = 1
' Search sphere intersect
t = intersec(cam, ctr, r)
' Found
IF t > 0 AND cam.y * t > pln.y THEN
' Calculate normal and point of intersect
mul3vec cam, t ' cam *= t
sub3vec nor, cam, ctr ' nor = cam - ctr
sub3vec lno, lpt, cam ' lno = lpt - cam
mul3vec cam, -1 ' cam = -cam
' Normalize vectors
normvec3 nor
normvec3 cam
normvec3 lno
' Reflect camera & normal
refl = 2 * mul3(cam, nor)
ref.x = refl * nor.x - cam.x
ref.y = refl * nor.y - cam.y
ref.z = refl * nor.z - cam.z
normvec3 ref
' Directional and specular
ldir = mul3(nor, dir): IF ldir < 0 THEN ldir = 0
lspe = mul3(ref, lno): IF lspe < 0 THEN lspe = 0 ELSE lspe = lspe ^ 7
' Total Light
lv = ldir * .8 + lspe * .5
IF lv < 0 THEN lv = 0
IF lv > 1 THEN lv = 1
PSET (sx, sy), lv * 63 + 64
ELSE
' Only floor
IF y < 0 THEN
IF cam.y = 0 THEN cam.y = 1
' Point of intersection of floor
pln.z = pln.y / cam.y
pln.x = cam.x * pln.z
u = INT(pln.x)
v = INT(pln.z)
c = ((v + move) XOR (u + 16)) AND 63
c = 16 * c / pln.z
IF c > 63 THEN c = 63
' Search intersection of ball, light and floor
sub3vec ctn, ctr, pln
sub3vec ltn, lpt, pln
' --------------------------------------
' LTN = LPT (Light Pointer) - Plane(XYZ)
' CTN = CTR (Center Sphere) - Plane(XYZ)
' --------------------------------------
t = intersec(ltn, ctn, r)
IF t > 0 THEN c = c \ 2
PSET (sx, sy), 64 + c
ELSE
PSET (sx, sy), 0
END IF
END IF
NEXT
NEXT
' I like'd moved moved!
move = move + 1
WEND
FUNCTION intersec (cam AS vec3, ctr AS vec3, r AS SINGLE)
a = mul3(cam, cam)
b = -mul3(cam, ctr) * 2
c = mul3(ctr, ctr) - r ^ 2
d = b ^ 2 - 4 * a * c
t = 0
IF d >= 0 THEN
d = SQR(d)
t1 = (-b - d) / (2 * a)
t2 = (-b + d) / (2 * a)
IF t1 < 0 AND t2 < 0 THEN t = -1
IF t1 < 0 AND t2 > 0 THEN t = t2
IF t1 > 0 AND t2 < 0 THEN t = t1
IF t1 > 0 AND t2 > 0 THEN
IF t1 < t2 THEN t = t1 ELSE t = t2
END IF
END IF
intersec = t
END FUNCTION
FUNCTION length (a AS vec3)
length = SQR(mul3(a, a))
END FUNCTION
FUNCTION mul3 (a AS vec3, b AS vec3)
mul3 = a.x * b.x + a.y * b.y + a.z * b.z
END FUNCTION
SUB mul3vec (v AS vec3, k AS SINGLE)
v.x = v.x * k
v.y = v.y * k
v.z = v.z * k
END SUB
SUB sub3vec (c AS vec3, a AS vec3, b AS vec3)
c.x = a.x - b.x
c.y = a.y - b.y
c.z = a.z - b.z
END SUB
SUB normvec3 (v AS vec3)
mul3vec v, 1 / length(v)
END SUB
SUB SetPal
FOR i = 0 TO 63
OUT 968, i + 64
OUT 969, i
OUT 969, i
OUT 969, i
NEXT
END SUB