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This thread is locked; no one can reply to it.
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| Moving a game object- Cos, Sin, Tan |
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Eman_321
Member #12,300
October 2010
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Hi! When I turn a player at a specified angle..I need to able to make the player move in the direction at which i am facing. I tried finding the new coordinates by using
angle = 0.0f;
new_x = cos(angle) * radius ;
new_y = sin(angle) * radius ;
angle+=0.1f;//or minus depending on which key i am pressing(LEFT or RIGHT)
rotate_sprite(..) ;
that should give me the new x and y direction for controlled player to move it.. First question I want to know is why is 0.0 the starting angle? do I have to convert to degrees to get the proper x and y values..i tried both and either it doesn't move or it gets stuck.. How can I turn my player using the keys and the move in that direction Can anyone draw a little diagram to help me understand this?
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X-G
Member #856
December 2000
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Eman_321 said: But if I was to add the old vector to the new one..it could "jump" and will get stuck at the (0,0) corner of the screen.
That is what you should to do. Without some actual code and a better description of what isn't working, there is nothing else we can do. -- |
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Eman_321
Member #12,300
October 2010
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Sorry, my bad 1
2#include <allegro.h>
3#include "Vector2.h"
4#include <cmath>
5#define PI 3.14159276535
6int main()
7{
8 Vector2 pos1(320,100) ;
9
10 Vector2 pos2(-2,-2) ;
11 float new_x=0.0f ;
12 float new_y = 0.0f;
13
14 float angle =0.0f ;
15
16
17 float length = 0;
18 if(!allegro_init())
19 {
20 BITMAP* backbuffer = create_bitmap(640,480) ;
21 BITMAP* playerOne = create_bitmap(20,20) ;
22 BITMAP* playerTwo = create_bitmap(20,20) ;
23
24
25 install_keyboard() ;
26 // set_color_depth(32) ;
27
28 clear_to_color(playerOne,makecol(0,0,0));
29
30
31 clear_to_color(playerTwo,makecol(0,0,0));
32
33
34
35
36 if(!set_gfx_mode(GFX_AUTODETECT_WINDOWED,640,480,0,0))
37 {
38 while(!key[KEY_ESC])
39 {
40 clear_to_color(backbuffer,makecol(0,0,0));
41
42 triangle(playerOne,0,19,10,0,19,19,makecol(255,255,255));
43 triangle(playerTwo,0,19,10,0,19,19,makecol(255,255,255));
44
45
46
47
48
49 length = sqrt(pos1.x*pos1.x + pos1.y * pos1.y) ;
50
51
52 if(key[KEY_RIGHT])
53
54 {
55 angle+=0.1f;
56
57 }
58
59 if(key[KEY_LEFT])
60
61 {
62 angle-=0.1f;
63
64
65 }
66
67
68
69
70 if(key[KEY_UP])
71 {
72
73
74 pos1.x-=new_x;
75
76 pos1.y-=new_y;
77
78 }
79
80
81
82
83
84
85
86
87 target_angle = atan2(pos1.y,pos1.x) ;
88
89 new_x = length * cosf(target_angle) ;
90 new_y = length * sinf(target_angle);
91 target_angle+=1 ;
92
93
94
95
96 rotate_sprite(backbuffer,playerOne,pos1.x ,pos1.y,ftofix(angle)) ;
97
98 draw_sprite(backbuffer,playerTwo,pos2.x,pos2.y) ;
99
100
101 clear_to_color(playerOne,makecol(0,0,0));
102
103
104
105
106
107 clear_to_color(playerOne,makecol(255,0,0));
108
109
110 blit(backbuffer,screen,0,0,0,0,SCREEN_W,SCREEN_H) ;
111 clear_bitmap(backbuffer) ;
112 }
113 }
114 }
115 return 0 ;
116}
vector2 just has x and y coordinates nothing more.
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gnolam
Member #2,030
March 2002
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And are those coordinates integers or floats? -- |
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Eman_321
Member #12,300
October 2010
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1
2
3#ifndef Vector2_h
4#define Vector2_h
5class Vector2
6{
7public:
8 float x ;
9 float y ;
10 float angle ;
11
12public:
13 float length() ;
14 void normalize(float l) ;
15
16 Vector2(float,float) ;
17
18 void add(Vector2 &pos) ;
19 void subtract(Vector2 &pos) ;
20 void scale(float f) ;
21
22 float direction() ;
23
24 void setAngle(float f) ;
25
26 void getVectors();
27} ;
28#endif
29#include <math.h>
30#include "Vector2.h"
31#include <allegro.h>
32float Vector2::length()
33{
34 return sqrt(x*x + y*y) ;
35}
36
37void Vector2::normalize(float l)
38{
39 x = x/l ;
40 y = y/l ;
41}
42
43Vector2::Vector2(float x,float y)
44{
45 this->x = x;
46 this->y = y;
47}
48
49void Vector2::add(Vector2 &pos)
50{
51 x +=pos.x ;
52 y+=pos.y ;
53}
54void Vector2::subtract(Vector2 &pos)
55{
56 x -=pos.x ;
57 y-=pos.y ;
58
59}
60void Vector2::scale(float f)
61{
62
63 x *=f ;
64 y*=f ;
65}
66
67void Vector2::getVectors()
68{
69 textprintf(screen,font,320,10,makecol(255,0,0),"Pos X: %f %f", x, y) ;
70
71}
72float Vector2::direction()
73{
74 angle = atan(y/x) ;
75
76 return angle ;
77
78}
79void Vector2::setAngle(float x1)
80{
81 //angle+=x1 ;
82}
That is Vector.h and Vector.cpp combined..
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Trezker
Member #1,739
December 2001
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In direction, it's better to use atan2(y, x) since that handles special cases. And you know you can overload operators right? |
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Eman_321
Member #12,300
October 2010
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i haven't gone past polymorphism haha i know i can use atan2(..) or sin(..) ... why is the angle set to 0.0f? why is it incremented? Does angle represent degrees or is it just a simple unit? How can i move the player object in the direction to which i am facing? Thanks for help
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gnolam
Member #2,030
March 2002
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Eman_321 said: why is the angle set to 0.0f
Because... you've initialized it to 0.0f? Quote: why is it incremented?
Again, you are the one doing it. Quote: Does angle represent degrees or is it just a simple unit? Quote: How can i move the player object in the direction to which i am facing?
-- |
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Eman_321
Member #12,300
October 2010
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mmn.. the last parameter takes a fixed angle. In some examples they use 90,64,128...some 0.0f you give me this equation
which angle do I use? angle I have set to rotate about how come you aren't multiplying by magnitude?
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OnlineCop
Member #7,919
October 2006
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Allegro uses fixed math for its directions. So 256 fixed is 360.0 degrees or 2*PI radians. The examples you're seeing are taking into account that 0..64 gives angles from 0..90 degrees (or 0..PI/2 radians) in order for things such as rotate_sprite() to allow the object to face in the correct direction. There are two ways to do your movements. You can use cartesian coordinates (x,y) or polar (theta, magnitude). They will equal the same in the end, but lets you choose which math you want to use to get there.
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Eman_321
Member #12,300
October 2010
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I have used this diagram to try and explain the angle concept in allegro. 1
2#include <allegro.h>
3
4#include <cmath>
5
6
7class Vector2
8{
9public:
10 float x ;
11 float y ;
12 float angle ;
13
14public:
15 float length() ;
16 void normalize() ;
17
18 Vector2(float,float) ;
19
20 void add(Vector2 &pos) ;
21 void subtract(Vector2 &pos) ;
22 void scale(float f) ;
23
24 float direction() ;
25
26 void setAngle(float f) ;
27
28
29} ;
30
31float Vector2::length()
32{
33 return sqrt(x*x + y*y) ;
34}
35
36void Vector2::normalize()
37{
38 float l=length() ;
39 x = x/l ;
40 y = y/l ;
41}
42
43
44
45void Vector2::add(Vector2 &pos)
46{
47 x +=pos.x ;
48 y+=pos.y ;
49}
50void Vector2::subtract(Vector2 &pos)
51{
52 x -=pos.x ;
53 y-=pos.y ;
54
55}
56void Vector2::scale(float f)
57{
58
59 x *=f ;
60 y*=f ;
61}
62float Vector2::direction()
63{
64 angle = atan(y/x) ;
65
66 return angle ;
67
68}
69void Vector2::setAngle(float x1)
70{
71 //angle+=x1 ;
72}
73
74#ifndef M_PI
75 #define M_PI 3.1415926535897932385
76
77#endif
78int main()
79{
80 Vector2 pos1(320,100) ;
81
82 Vector2 pos2(-2,-2) ;
83 float new_x=0.0f ;
84 float new_y = 0.0f;
85
86 float angle =0.0f ;
87 float target_angle=0.0f;
88
89 float length = 0;
90 if(!allegro_init())
91 {
92 BITMAP* backbuffer = create_bitmap(640,480) ;
93 BITMAP* playerOne = create_bitmap(20,20) ;
94 BITMAP* playerTwo = create_bitmap(20,20) ;
95
96
97 install_keyboard() ;
98
99
100
101 clear_to_color(playerOne,makecol(0,0,0));
102
103
104 clear_to_color(playerTwo,makecol(255,0,0));
105
106 triangle(playerOne,0,19,10,0,19,19,makecol(255,255,255));
107 triangle(playerTwo,0,19,10,0,19,19,makecol(255,255,255));
108
109
110
111
112 if(!set_gfx_mode(GFX_AUTODETECT_WINDOWED,640,480,0,0))
113 {
114 while(!key[KEY_ESC])
115 {
116 clear_to_color(backbuffer,makecol(0,0,0));
117
118
119
120
121
122
123 triangle(playerOne,0,19,10,0,19,19,makecol(255,255,255));
124
125 triangle(playerTwo,0,19,10,0,19,19,makecol(255,255,255));
126
127 length = sqrt(pos1.x*pos1.x + pos1.y * pos1.y) ;
128
129
130 if(key[KEY_RIGHT])
131 {
132 if(angle>=256.0f)
133 {
134 angle = 256.0f;
135 }
136 angle= angle +0.1f ;
137 }
138
139
140
141 if(key[KEY_LEFT])
142 {
143
144 if(angle<=0.0f)
145 {
146 angle = 0.0f;
147 }
148 angle= angle - 0.1f;
149 }
150
151
152 if(key[KEY_UP])
153 {
154 pos1.x += sin(angle * M_PI/180)*1;
155 pos1.y += cos(angle * M_PI/180)*-1;
156 }
157 if(key[KEY_DOWN])
158 {
159 pos1.x -= sin(angle * M_PI/180)*1;
160 pos1.y -= cos(angle * M_PI/180)*-1 ;
161 }
162
163
164 //target_angle = atan2(pos1.x,pos1.y) ;
165
166 textprintf(backbuffer,font,320,10,makecol(255,0,0),"Angle: %f", angle) ;
167
168
169
170
171
172
173 rotate_sprite(backbuffer,playerOne,pos1.x ,pos1.y,ftofix(angle)) ;
174
175
176 draw_sprite(backbuffer,playerTwo,pos2.x,pos2.y) ;
177
178
179 clear_to_color(playerOne,makecol(0,0,0));
180
181
182
183
184
185 clear_to_color(playerTwo,makecol(0,0,0));
186
187
188 blit(backbuffer,screen,0,0,0,0,SCREEN_W,SCREEN_H) ;
189 clear_bitmap(backbuffer) ;
190 }
191 }
192 }
193 return 0 ;
194}
195
196END_OF_MAIN()
The player moves in the right direction only if its angle is between 0 and 64 degrees, after that it doesn't move in the right direction..
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Mark Oates
Member #1,146
March 2001
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I'm suprised nobody's mentioned Amarillion's Legendary Sin & Cos Tutorial. -- |
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Eman_321
Member #12,300
October 2010
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I read it already. I get how to convert from polar to cartesian and vice versa.
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gnolam
Member #2,030
March 2002
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Eman_321 said: how come you aren't multiplying by magnitude?
I am. move_speed_per_tick. Eman_321 said: rotate_sprite(backbuffer,playerOne,pos1.x ,pos1.y,ftofix(angle));
ftofix() only converts a float into fixed point - it doesn't change the angle representation. You're trying to pass in degrees (0-360) instead of allegro angles (0-256) to rotate_sprite(). Eman_321 said: like why is the initial angle set to 0
... arrrgh. Because you fucking set it to 0. -- |
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Eman_321
Member #12,300
October 2010
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Quote: arrrgh. Because you ****ing set it to 0.
EDIT I understand calculating the angles and cartesian coordinates!
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yes i know i set it to 0, what i don't get is