Smooth Sprite Movement

[Zeppelin]

Hey everyone,
Heres a good starting point or example for anyone having problems with slow or jerky sprite movement.

Code: QB64: [Select]

1. [/cod_TITLE "Space Invaders"
2. _SCREENMOVE _MIDDLE
3. SCREEN 13 '320x200
4.  
5. 'LOAD SPRITES
6. DIM SHARED alien1%(1000)
7. DIM SHARED alien2%(1000)
8. DIM SHARED alien3%(1000)
9.  
10. DIM SHARED shield%(1000)
11. DIM SHARED player%(1000)
12.  
13. TYPE Bullet
14.     xPos AS INTEGER
15.     yPos AS INTEGER
16.     alive AS INTEGER
17. END TYPE
18.  
19. DIM SHARED bullets(100) AS Bullet
20.  
21. DIM SHARED deltaTime
22. DIM SHARED playerSpeed
23. DIM SHARED bulletSpeed
24. DIM SHARED lastBulletTime
25.  
26. DIM SHARED pX
27.  
28. CALL LoadSprite(alien1%())
29. CALL LoadSprite(alien2%())
30. CALL LoadSprite(alien3%())
31.  
32. CALL LoadSprite(shield%())
33. CALL LoadSprite(player%())
34.  
35. playerSpeed = 100
36. bulletSpeed = 100
37.  
38. FOR n = 1 TO 100
39.     bullets(n).alive = 0
40. NEXT n
41.  
42. CALL DrawShields
43.  
44. DO
45.     sTime = TIMER
46.  
47.     CALL MovePlayer
48.     CALL SpawnBullet
49.     CALL UpdateBullets
50.  
51.  
52.     eTime = TIMER
53.     deltaTime = eTime - sTime
54. LOOP UNTIL INKEY$ = CHR$(27)
55.  
56. SUB UpdateBullets
57.     FOR n = 1 TO 100
58.         IF bullets(n).alive = 1 THEN
59.             LINE (bullets(n).xPos, bullets(n).yPos)-(bullets(n).xPos + 2, bullets(n).yPos + 4), _RGB(0, 0, 0), BF
60.             bullets(n).yPos = bullets(n).yPos - (deltaTime * bulletSpeed)
61.             LINE (bullets(n).xPos, bullets(n).yPos)-(bullets(n).xPos + 2, bullets(n).yPos + 4), _RGB(255, 0, 0), BF
62.             _DISPLAY
63.  
64.             IF bullets(n).yPos < 0 THEN
65.                 bullets(n).alive = 0
66.                 LINE (bullets(n).xPos, bullets(n).yPos)-(bullets(n).xPos + 3, bullets(n).yPos + 5), _RGB(0, 0, 0), BF
67.             END IF
68.  
69.         END IF
70.     NEXT n
71. END SUB
72.  
73. SUB SpawnBullet
74.     IF _KEYDOWN(32) = -1 THEN
75.         IF TIMER - lastBulletTime > 0.1 THEN
76.             first = 101
77.             FOR n = 100 TO 1 STEP -1
78.                 IF NOT bullets(n).alive = 1 THEN
79.                     IF n < first THEN
80.                         first = n
81.                     END IF
82.                 END IF
83.             NEXT n
84.  
85.             IF first < 101 THEN
86.                 lastBulletTime = TIMER
87.                 bullets(first).alive = 1
88.                 bullets(first).xPos = pX + 5
89.                 bullets(first).yPos = 170
90.                 LINE (bullets(first).xPos, bullets(first).yPos)-(bullets(first).xPos + 2, bullets(first).yPos + 4), _RGB(255, 255, 255), BF
91.             END IF
92.         END IF
93.     END IF
94. END SUB
95.  
96. SUB MovePlayer
97.     IF _KEYDOWN(100) = -1 THEN
98.         pX = pX + (deltaTime * playerSpeed)
99.     END IF
100.     IF _KEYDOWN(97) = -1 THEN
101.         pX = pX - (deltaTime * playerSpeed)
102.     END IF
103.  
104.     IF pX < 20 THEN
105.         pX = 20
106.     END IF
107.     IF pX > 300 THEN
108.         pX = 300
109.     END IF
110.  
111.     LINE (pX - 10, 175)-(pX + 100, 201), _RGB(0, 0, 0), BF
112.     PUT (pX, 175), player%()
113.     _DISPLAY
114. END SUB
115.  
116. SUB DrawShields
117.     FOR x = 0 TO 3
118.         PUT (x * (320 / 4) + 30, 150), shield%()
119.     NEXT x
120. END SUB
121.  
122. SUB LoadSprite (sp%())
123.     DIM sprite(4, 4)
124.     scale = 2
125.     FOR y = 0 TO 4
126.         FOR x = 0 TO 4
127.             READ sprite(x, y) 'Read the data
128.         NEXT x
129.     NEXT y
130.  
131.     FOR y = 0 TO 4 * scale STEP scale 'Factor in the scale
132.         FOR x = 0 TO 4 * scale STEP scale
133.             LINE (x, y)-(x + scale, y + scale), sprite(x / scale, y / scale), BF 'Draw each pixel
134.         NEXT x
135.     NEXT y
136.  
137.     GET (0, 0)-(10, 10), sp%()
138.     CLS
139. END SUB
140.  
141. 'Alien 1 Data
142. DATA 0,0,15,0,0
143. DATA 0,15,15,15,0
144. DATA 0,15,15,15,0
145. DATA 15,0,15,0,15
146. DATA 0,15,0,15,0
147.  
148. 'Alien 2 Data
149. DATA 0,0,15,0,0
150. DATA 0,15,15,15,0
151. DATA 0,15,0,15,0
152. DATA 15,0,0,0,15
153. DATA 15,0,0,0,15
154.  
155. 'Alien 3 Data
156. DATA 15,0,0,0,15
157. DATA 15,0,15,0,15
158. DATA 0,15,0,15,0
159. DATA 0,15,0,15,0
160. DATA 0,0,15,0,0
161.  
162. 'Shield Data
163. DATA 0,15,15,15,0
164. DATA 15,15,15,15,15
165. DATA 15,15,0,15,15
166. DATA 15,0,0,0,15
167. DATA 15,0,0,0,15
168.  
169. 'Player Data
170. DATA 0,0,0,0,0
171. DATA 0,0,15,0,0
172. DATA 0,15,15,15,0
173. DATA 15,15,15,15,15
174. DATA 15,15,15,15,15
175.  
176. e]
177.  
178. Yes. It is for a space invaders clone im making.
179.  
180. Zep