Kordinate Calculation with trigonometri

and do you have a cordinat for the center og the tank... that would indeen help a lot...

Morten

Hello Morten!
Yes the center is also known:
centerX = gameWindowWidth/2
centerY = gameWindowHeight/2
That is also the center of the tank.
Best regards
Fredrik

The following is untested but taken from a tutorial on 2d transformation, translocation and rotation...

If one defines four corners - calling them
  NorthWest, NorthEast, SouthWest and SouthEast

then the coordinates at 0 degrees twisting would be
NW ( centerX - 0.5*tankWidth, centerY - 0.5*tankHeight );
NE ( centerX + 0.5*tankWidth, centerY - 0.5*tankHeight );
SW ( centerX - 0.5*tankWidth, centerY + 0.5*tankHeight );
SE ( centerX + 0.5*tankWidth, centerY + 0.5*tankHeight );

Then - if centerX and centerY is set as the point of origin for the rotation, the coordinates for the points vill be
NW ( -0.5*tankWidth, -0.5*tankHeight );
NE ( 0.5*tankWidth, -0.5*tankHeight );
SW ( -0.5*tankWidth, 0.5*tankHeight );
SE ( 0.5*tankWidth, 0.5*tankHeight );

one can then use the two rotation formulas
  x' = cos(v) x - sin(v) y
  y' = sin(v) x + cos(v) y

lets say, that the coordinate for SE is (5, 8) and the angle is 45 degrees
then the SE point after rotation will be
  ( cos(45)*5 - sin(45)*8 , sin(45)*5 + cos(45)*8 )
or
  ( -4 , 0 ) approx

these coordinates are then translocated to the center again be adding centerX and centerY accordingly....

Hope this helps...

/Søren

Hmmm seems like i've made a bit of a bug there.... (my calculator was set to radians instead of degrees...)

the correct result for point(5,8) after a rotation af 45 degrees should be
  x' = 5 cos 45 - 8 sin 45 = -2.1213
  y' = 5 sin 45 + 8 cos 45 =  9.1923

so the resulting point would be (-2, 9)

/Søren

PS: a tip when translating to a computerscreen - after you are done rotating your points then use negative y values ( multiply your y coordinates with -1) ... In a graph - the y axis increments upwards, while the y axis on a computerscreen increments downwards ... therefore the "MULTIPLY -1 on y coordinates" tip :-)

remember, that rotation is counter-clockwise - if you desire clockwise rotation, you can use -1*angle as angle

Answer .... Could you use the formulas ???

Hello Soren!
I should try to implement your formulas as soon as possible, I bet it will work.

I'll be back!
Thanks
Fredrik

Thanks

thanks for the points - were you able to use the formulas ?