Problem with Grouping the rotated object.
Hi All,
We are developing a kind of drawing application in Objective C using Cocoa
framework. We have several separate graphical objects, each having their own
position and rotation angle, are then grouped. As soon as we group the
objects the rotated object has got shift with their angle. This happen only
with rotated object. Below is the code snippet that we are using.
NSRect stRect = NSZeroRect;
NSArray *objTlGraphic = [[self document] graphics];
unsigned iIndex, nCount =[objTlGraphic count];
if(in_Group != 0)
{
for(iIndex = 0; iIndex nCount; iIndex ++)
{
if([[objTlGraphic objectAtIndex:i] GroupNO] == in_Group)
{
stRect =NSUnionRect(stRect,[[objTlGraphic objectAtIndex:
iIndex] bounds]);
}
}
}
NSAffineTransform* xform = [NSAffineTransform transform];
[currentContext saveGraphicsState];
[NSBezierPath clipRect:drawingBounds];
NSPoint center = NSMakePoint(NSMidX(stRect), NSMidY(stRect));
[xform translateXBy:center.x yBy:center.y];
[xform rotateByDegrees:[curGraphic GetAngle]];
[xform translateXBy:-center.x yBy:-center.y];
[xform concat];
Any one tells me what I'm missing here.
Thanks,
Ghufran Ahmad
+91 - 9953130470
Skype ID: ghufran_khan81
AOL ID: gahmad81
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Re: Problem with Grouping the rotated object.
That's not enough code to go on — it's not showing all the drawing. Are you remembering to restore the saved graphics state after you finish drawing an object? Also, if you could paste in the code without the extra blank lines, it would make it more readable. —Jens smime.p7s Description: S/MIME cryptographic signature ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
Re: Problem with Grouping the rotated object.
On Apr 2, 2008, at 04:00, Ghufran Ahamad wrote: NSAffineTransform* xform = [NSAffineTransform transform]; [currentContext saveGraphicsState]; [NSBezierPath clipRect:drawingBounds]; NSPoint center = NSMakePoint(NSMidX(stRect), NSMidY(stRect)); [xform translateXBy:center.x yBy:center.y]; [xform rotateByDegrees:[curGraphic GetAngle]]; [xform translateXBy:-center.x yBy:-center.y]; [xform concat]; This looks kind of wrong. Mathematically, wouldn't you want: [xform translateXBy:-center.x yBy:-center.y]; [xform rotateByDegrees:[curGraphic GetAngle]]; [xform translateXBy:center.x yBy:center.y]; ? ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
Re: Problem with Grouping the rotated object.
Quincey Morris wrote: On Apr 2, 2008, at 04:00, Ghufran Ahamad wrote: [xform translateXBy:center.x yBy:center.y]; [xform rotateByDegrees:[curGraphic GetAngle]]; [xform translateXBy:-center.x yBy:-center.y]; This looks kind of wrong. Mathematically, wouldn't you want: [xform translateXBy:-center.x yBy:-center.y]; [xform rotateByDegrees:[curGraphic GetAngle]]; [xform translateXBy:center.x yBy:center.y]; ? Nope. The way the matrix multiplication works, the effect is that the transformations take place in the opposite order of the way they appeared in code. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
Re: Problem with Grouping the rotated object
Let me explain how we are handling grouped objects. We have only one basic type of draw object with a dictionary of characteristics. That gives a lot of flexibility. We do not let objects draw themselves. Instead, we use a separate rendering object. This results in a clean object data model. (Hopefully, this will help when we do Windows.) We use an object of type group to replace grouped objects. When the renderer encounters a group type object, it creates another temporary renderer object that draws the group. This allows recursion for groups. Of course, the group object has to compute it's own bounds, including internal and total rotations. So far, this works quite well and we haven't encountered the problem you have had. Message: 4 Date: Wed, 2 Apr 2008 16:30:42 +0530 From: Ghufran Ahamad [EMAIL PROTECTED] Subject: Problem with Grouping the rotated object. To: cocoa-dev@lists.apple.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain;charset=us-ascii Hi All, We are developing a kind of drawing application in Objective C using Cocoa framework. We have several separate graphical objects, each having their own position and rotation angle, are then grouped. As soon as we group the objects the rotated object has got shift with their angle. This happen only with rotated object. Below is the code snippet that we are using. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
