> ----- Original Message ----- > From: "Kevin Fishburne"<kevinfishbu...@eightvirtues.com> > To: gambas-user@lists.sourceforge.net > Sent: Tuesday, 22 May, 2012 5:14:02 AM > Subject: [Gambas-user] gb3: OpenGL Rotate and Translate logic > > Disclaimer: I've been working on this for days and neither Google nor > trial and error is adequate, apparently. > > I'm trying to render an overhead, 2D scene with the "camera" at the > center of the screen and the world objects rotated around it. Here are > my variables: > > Camera.WorldX As Single ' World coordinates of camera. > Camera.WorldYAs Single ' World coordinates of camera. > Camera.Orientation As Single ' Angle of camera (2D overhead view, > rotates screen like Contra III for SNES). > Camera.Zoom As Single ' Scale of matrix for zooming in and out. > sWidth As Short ' Width in pixels of screen. > sHeight As Short ' Height in pixels of screen. > > I need to rotate the matrix so that rendered objects will appear in the > correct positions with regard to the camera's orientation. I need to > translate the matrix so that the camera coordinates are always at the > center of the rendering window. I need to scale the matrix so that the > camera can zoom in and out (always centered at the middle of the > rendering window). > > I suspect that to center the camera on the rendering window after > rotating the matrix, I need to "unrotate" the x and y offsets required > to center it, which I can do if necessary using some functions I created > to rotate an arbitrary point about an arbitrary origin. > > I think I can successfully rotate the matrix around the camera with code > like this: > > Gl.Translatef(Camera.WorldX, Camera.WorldY, 0) > Gl.Rotatef(- Camera.Orientation, 0, 0, 1) > Gl.Translatef(- Camera.WorldX, - Camera.WorldY, 0) > > But then I need to translate the scene so that the camera is in the > center of the rendering window. I also can't figure out how to > arbitrarily scale the matrix to zoom in and out on the camera in this > sequence. I have this: > > Gl.Scalef(128 * Zoom.Current, 128 * Zoom.Current, 1) > > but its effects vary depending on where I place it. The reason it > multiplies by 128 is because each "tile" is 128 pixels, and each world > coordinate is one tile. I couldn't be more confused if I'd just been > shot in the head, so any help is greatly appreciated. >
On 05/22/2012 03:02 AM, tommyl...@eircom.net wrote: > Hi Kevin. > > There's plenty of issues you post, but first thing I would do would be: > > instead of: > > Gl.Translatef(Camera.WorldX, Camera.WorldY, 0) > Gl.Rotatef(- Camera.Orientation, 0, 0, 1) > Gl.Translatef(- Camera.WorldX, - Camera.WorldY, 0) '<<-- you come back > along different path here because > 'the world is turned > along z-axis > > > try this: > > Gl.Translatef(Camera.WorldX, Camera.WorldY, 0) > gl.PushMatrix() '<-you save the world's > coordinate here > > do all the drawing here > > gl.PopMatrix() '<-restore camera's > original position. > > > > Doing gl.Rotatef() you turn GLOBAL coordinates, so if you do > gl.Rotatef(90,0,0,1), your x an y axes are swapped, y becomes x, becomes -y, > thus doing gl.Translatef(1,1,0) next in fact moves your object by (-1,1,0...I > think:)) ). > That's for the moment, the rest we can discuss if you want. > > regards > > Tomek > Hi Tomek. I'm not sure that saving and loading the matrix will do the trick, but I don't really understand the implications of doing so either. I basically want to translate, scale and rotate the matrix so that the camera is always at the center of the render window and I can draw objects using their native world coordinates. The camera is pointing straight down at the ground (perpendicular to the landscape). Rotating the camera/matrix will spin the landscape with the camera being the origin, just like spinning a globe of Earth if the camera is pointing down at the north pole. It would look something like this: http://www.youtube.com/watch?v=mee_FiIQoEY If I do this below everything is perfect (including zoom) but it has no rotation: ' Rotate, translate and scale matrix. ScreenOffsetX = sWidth / 2 / 128 / Zoom.Current ScreenOffsetY = sHeight / 2 / 128 / Zoom.Current Gl.LoadIdentity() Gl.Scalef(128 * Zoom.Current, 128 * Zoom.Current, 1) Gl.Translatef(- Camera.WorldX + ScreenOffsetX, - Camera.WorldY + ScreenOffsetY, 0) Incorporating rotation rotates the scene but not around the camera. Using the above code and then rendering everything at its native world coordinates looks like this: http://eightvirtues.com/sanctimonia/misc/Everything%20But%20Rotation.ogv If necessary I can translate the matrix by (x,y) units which have been pre-rotated opposite the angle the matrix was rotated at. I can basically manually "undo" the matrix rotation if it needs to be translated post rotation, if that makes any sense. Some instinct inside me keeps nagging that I might need to do a trick like that to get it to work. -- Kevin Fishburne Eight Virtues www: http://sales.eightvirtues.com e-mail: sa...@eightvirtues.com phone: (770) 853-6271 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Gambas-user mailing list Gambas-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gambas-user
