Moving Objects in direction of an angle

[hannes]

Hi!

I want to Move an Object (in 2D) in the direction of a specified angle.
In the past I used something like this:

x :=x + Round(Cos256(angle)*Speed);
y :=y + Round(Sin256(angle)*Speed);

(Cos/Sin256 are from DelphiX)
But this allows only an angle from 0 to 255.

Ho can I realize this for 0 to 360A¬

[WiZz]

X:=x+cos(Angle);
Y:=Y+sin(Angle);

[hannes]

*g* I have already tried this before, but it doesn't work..
It leads to weird, random-like results..

[Paulius]

I'm just guessing, but you're probably doing the rounding in a wrong place, keep you're x and y as real numbers (singles preferably) and only use them rounded when drawing, or you're forgetting that the angle is in radians.

[hannes]

Hm this doesn't fix the problem

With each increase oder decrease of the angle, the object moves in a totally different direction..

I know that there are more Cos/Sin function than just Cos()..
..maybe Cos256 is based on something different..

[Paulius]

Post yore angle changing code

[hannes]

ok here we go:

if &#40;links&#41; AND &#40;angle < 360&#41; then angle &#58;= angle +1;
if &#40;rechts&#41; AND &#40;angle > 0&#41; then angle &#58;= angle -1;

if &#40;links&#41; AND &#40;angle = 360&#41; then angle &#58;= 0;
if &#40;rechts&#41; AND &#40;angle = 0&#41; then angle &#58;= 360;

links & rechts are checked in OnKeyDown links is true if VK_LEFT is pressed and rechts if VK_RIGHT..
(Undone in OnKeyUp)

[Paulius]

I know that there are more Cos/Sin function than just Cos()..
..maybe Cos256 is based on something different..

Nope, checked DelphiX?¢_Ts source, Cos256 simply uses a lookup table precalculated with
for i:=0 to 255 do
CosinTable[i] := Cos((i/256)*2*PI);

As I said the angle is in radians, so changing it by 1 is rotating by a almost 60 degrees, change the angle in much smaller values like one degree (that is pi/180).

[hannes]

Ah ok thanks, now it is close to a "realistic" movement.

I'm doing It like this:

(Angle is increased as done before)

xko :=xko - Cos(360-angle*(pi/180))*Speed;
yko :=yko + Sin(360-angle*(pi/180))*Speed;

but the movement in a 90A¬? angle is not totally correct, maybe 10A¬? more than it should be..

I have uploaded the thing i am working on here:
(it is a modified delphiGL example)
http://www.siedla-design.de/space.zip
Please have a short look..

[Paulius]

yore not converting 360 degrees to radians in 360-angle*(pi/180), it should be (360-angle)*(pi/180). To say the truth 360 is not needed at all. And keeping the angle variable in radians would be a tiny bit faster than converting from degrees every time you use trigonometry.