trigonometry the solution to spinning image?

Blitz3D Forums/Blitz3D Programming/trigonometry the solution to spinning image?

stanrol

(Posted 2010) [#1]

how do I make an image rotate and spin around in the same place?
I know you use cos() and sine.

Matty

(Posted 2010) [#2]

Are you using 3d commands or 2d commands?

Do you want the image to rotate about its centre, or an arbitrary point in 2d? or 3d? space?

stanrol

(Posted 2010) [#3]

2d and around it's centre.

Matty

(Posted 2010) [#4]

For real time usage it is better to 'precalculate' the rotations, ie rotate your image, and capture it as separate images for each angle.



;to rotate about centre
midhandle myimage

;change this to 0 or 1 to see the difference
tformfilter 0 ;1

;to rotate the image
rotateimage myimage,angle#

Warpy

(Posted 2010) [#5]

Yes, midhandle is the correct way to do this, but just for interest:

To draw the image with its centre at (x#,y#):

x= x-(ImageWidth(image)*cos(angle) + ImageHeight(image)*sin(angle))/2
y= y-(ImageWidth(image)*sin(angle) - ImageHeight(image)*cos(angle))/2

RotateImage image,angle
DrawImage image,x,y

(I've forgotten exactly how the b3d rotation commands work, but you get the idea)

Serpent

(Posted 2010) [#6]

Sadly the 2D image rotations can be horribly slow, so doing 2D rotations in realtime is not really a good idea, depending on what you're trying to achieve. If RotateImage isn't fast enough, you could do a '2D in 3D' type thing where you use 3D commands to draw your image.