Author Topic: Rotation (Read 4568 times)

ravenheart · « **on:** October 11, 2008, 04:04:40 pm »

hello, i want my sprite to rotate when the mouse is moved, so that my hero always looks in direction of MouseCursor

i tried following:

Code: [Select]


if( Event.Type == sf::Event::MouseMoved)
            {
                Vector2f Sprite_Mouse = GetMousePos() - v[0]->GetPosition();
                float angle = atan(Sprite_Mouse.x / Sprite_Mouse.y);
                v[0]->Rotate(angle);
            }

v[0] is a pointer to a sprite;
somehow it doesnt work exactly like i want it to , in the beginning it looks almost fine but when there is an angle of more tha 90° it goes crazy

how can i do what im trying to?

edit: in the beginning sometimes my sprite disappears

Laurent · « **Reply #1 on:** October 11, 2008, 07:07:08 pm »

atan function has 2 possible angles for the same value, use atan2 instead.

Code: [Select]

float angle = atan2(Sprite_Mouse.y, Sprite_Mouse.x)
(swap x and y if it's wrong)

ravenheart · « **Reply #2 on:** October 11, 2008, 07:12:18 pm »

same problem with both variants,

uis there any mathematical mistake? maybe GetPosition returns different points when its rotated?

is there any possibility to attach a video?

or can it be because my y-axe goes down in positive sense?

Laurent · « **Reply #3 on:** October 11, 2008, 08:24:44 pm »

You should use SetRotation rather than Rotate. Rotate adds to the previous angle, whereas SetRotation completely overwrite the current angle.

ravenheart · « **Reply #4 on:** October 11, 2008, 11:15:53 pm »

hmm i tried something i let my program write sprites x-pos, y-pos
then x and y-value of the vector mouse-sprite and then the calculated angle , an excerpt:

Sprite x: 0 Sprite y: 0 SM x: -173.75 SM y: -36.6667 angle: -2.93361
Sprite x: 0Sprite y: 0 SM x: -137.5 SM y: -5 angle: -3.10525
Sprite x: 0Sprite y: 0 SM x: -96.25 SM y: 31.6667 angle: 2.82374
Sprite x: 0Sprite y: 0 SM x: -48.75 SM y: 73.3333 angle: 2.1574

when i let this do my calculator, for example the first one

173.75 / 36.66 = 4,73 -> atan = 78° even in rad its 1.36

so i cannot explain whats happening :-(

ravenheart · « **Reply #5 on:** October 11, 2008, 11:49:18 pm »

o i managed it, atan was really in rad and i checked for division / 0 now , it works fine now

o no : now when mouse is in 4th quadrant the sprite points to 2nd
and same with 3rd when its there then the oicture shows 1st

but when mouse is in 1st or 2nd everythings ok

ravenheart · « **Reply #6 on:** October 11, 2008, 11:59:18 pm »

here my .txt:

Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 1.66667 angle: 86.8227
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 5 angle: 80.5401
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 10 angle: 71.5672
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 11.6667 angle: 68.7515
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 13.3333 angle: 66.0395
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 15 angle: 63.4368
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 16.6667 angle: 60.9472
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 18.3333 angle: 58.5722
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 20 angle: 56.3116
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 21.6667 angle: 54.1639
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 23.3333 angle: 52.1266
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 25 angle: 50.1959
Sprite x: 112.487Sprite y: 171.853 SM x: 30 SM y: 26.6667 angle: 48.3679
Sprite x: 112.487Sprite y: 171.853 SM x: 28.75 SM y: 26.6667 angle: 47.1544
Sprite x: 112.487Sprite y: 171.853 SM x: 28.75 SM y: 28.3333 angle: 45.4196
Sprite x: 112.487Sprite y: 171.853 SM x: 26.25 SM y: 30 angle: 41.1871
Sprite x: 112.487Sprite y: 171.853 SM x: 26.25 SM y: 31.6667 angle: 39.6581
Sprite x: 112.487Sprite y: 171.853 SM x: 25 SM y: 33.3333 angle: 36.871
Sprite x: 112.487Sprite y: 171.853 SM x: 22.5 SM y: 36.6667 angle: 31.5357
Sprite x: 112.487Sprite y: 171.853 SM x: 18.75 SM y: 40 angle: 25.1156
Sprite x: 112.487Sprite y: 171.853 SM x: 15 SM y: 41.6667 angle: 19.7995
Sprite x: 112.487Sprite y: 171.853 SM x: 12.5 SM y: 43.3333 angle: 16.0913
Sprite x: 112.487Sprite y: 171.853 SM x: 6.25001 SM y: 46.6667 angle: 7.62838
Sprite x: 112.487Sprite y: 171.853 SM x: 1.25001 SM y: 46.6667 angle: 1.5344
Sprite x: 112.487Sprite y: 171.853 SM x: -7.49999 SM y: 46.6667 angle: -9.13044
Sprite x: 112.487Sprite y: 171.853 SM x: -12.5 SM y: 46.6667 angle: -14.9955
Sprite x: 112.487Sprite y: 171.853 SM x: -16.25 SM y: 46.6667 angle: -19.1994
Sprite x: 112.487Sprite y: 171.853 SM x: -21.25 SM y: 46.6667 angle: -24.4832
Sprite x: 112.487Sprite y: 171.853 SM x: -23.75 SM y: 46.6667 angle: -26.9736
Sprite x: 112.487Sprite y: 171.853 SM x: -26.25 SM y: 46.6667 angle: -29.3586
Sprite x: 112.487Sprite y: 171.853 SM x: -27.5 SM y: 46.6667 angle: -30.5111
Sprite x: 112.487Sprite y: 171.853 SM x: -30 SM y: 43.3333 angle: -34.6962
Sprite x: 112.487Sprite y: 171.853 SM x: -32.5 SM y: 43.3333 angle: -36.871
Sprite x: 112.487Sprite y: 171.853 SM x: -36.25 SM y: 38.3333 angle: -43.4013
Sprite x: 112.487Sprite y: 171.853 SM x: -41.25 SM y: 36.6667 angle: -48.3679
Sprite x: 112.487Sprite y: 171.853 SM x: -43.75 SM y: 33.3333 angle: -52.6976
Sprite x: 112.487Sprite y: 171.853 SM x: -47.5 SM y: 28.3333 angle: -59.186
Sprite x: 112.487Sprite y: 171.853 SM x: -48.75 SM y: 25 angle: -62.8522
Sprite x: 112.487Sprite y: 171.853 SM x: -51.25 SM y: 20 angle: -68.6841
Sprite x: 112.487Sprite y: 171.853 SM x: -52.5 SM y: 18.3333 angle: -70.7526
Sprite x: 112.487Sprite y: 171.853 SM x: -53.75 SM y: 15 angle: -74.4094
Sprite x: 112.487Sprite y: 171.853 SM x: -56.25 SM y: 8.33333 angle: -81.5754
Sprite x: 112.487Sprite y: 171.853 SM x: -57.5 SM y: 5 angle: -85.0328

ravenheart · « **Reply #7 on:** October 12, 2008, 12:34:12 am »

i did some more experiments and have finally foud something working :

Code: [Select]


Vector2f Sprite_Mouse =  GetMousePos()  - v[1]->GetPosition()  ;
                if(Sprite_Mouse.y != 0)
                    angle = atan2(Sprite_Mouse.x, Sprite_Mouse.y);
                angle =  angle * 180 / 3.1415;
                angle = angle + 180 %360;
                v[1]->SetRotation(angle);

but WHY does this work?

Laurent · « **Reply #8 on:** October 12, 2008, 09:05:34 am »

Here is why it works :

Code: [Select]

if (Sprite_Mouse.y != 0)
    angle = atan2(Sprite_Mouse.x, Sprite_Mouse.y); // atan2 is the right function (atan is bad in this context)
angle =  angle * 180 / 3.1415; // convert to degrees for SFML
angle = angle + 180 % 360; // add 180 to map to SFML's drawing coordinates