Dear Michael, and others, I will take your advice and experiment with this modification of the KeyNavigator, however this is not our principal device. I actually detected the problem with the perspective projection in Java3D while I was wearing a see-through HMD tracked by an orientation tracker and a position tracker. These devices have been calibrated are reporting resonable results. Well, when I turn my head, so that I always see the real counterpart of 1 and 2 aligned, It is not the case with Java. However, like I said before, a rotation only is applied to the viewplatform. So this problem is not only related to the KeyNavigator. I can attach a picture if needed to understand the problem. Please try to experiment with that and you will see. Place a cube in the world (let say in 0, 0, 0 and of size 2 on any side). and place the viewplatform in (1, -5, 0) so that one side of the cube appears as a line. If you only rotate the transform applied to the viewplatform then you should always see this side as a line. In my case it does not work this way, I see the side as I turn. Any idea? Thanks Yohan >Date: Mon, 4 Oct 1999 16:51:38 -0700 >From: "Michael F. Deering" <[EMAIL PROTECTED]> >Subject: Re: PERSPECTIVE COMPUTATION, WRONG??? > >There is a "bug" in the current KeyNavigator.java code, depending on how >one wants to define the semantics of rotation. While a more complete >re-write is underway, a single line change we found may give the >behavior you want. > >Change the line: > vpQuat.mul(lrQuat, vpQuat); >to > vpQuat.mul(vpQuat, lrQuat); > >this will change the semantics from "rotate about the y-axis of the current >view platform coordinates" to "rotate about the y-axis of the current >world coordinates" which may be a more approprate semantics for you. Note >that this difference only applies if the page-up/down keys have been >pressed, if not, the y-axis of both coodrinates are the same. > >The changed semantics more closely match that of most computer games, in >which the page-up/down keys change the pitch of one's head in the virtual >environment, but do not change the angle of one's body relitive to the >ground plane. >>Dear developers, >> >>We are a viewplatform object connected to the scene graph and driven by a >>transformation >>generated by tracking devices to navigate in a virtual world. When we use >>the keyboard >>as input device, the right and left arrow are only turning the viewplatform >>around a vertical axis. >>I verified this fact by displaying the 4x4 matrix feeded to the viewplatform >>and verifying that >>only the 3x3 upper left components are modified. >> >>The problem I have is the following: I place two bulleyes in the world: 1 >>and 2. I translate the >>viewplatform in the world so that I see 1 and 2 as the same point: at this >>point my viewpoint >>is aligned with the line passing by 1-2. I then ONLY rotate the viewplatform >>using the direction >>keys. However, when I do that the viewpoint is clearly not doing only a >>rotation because >>1 and 2 are going appart from each others. This should not happen because if >>the >>viewpoint is doing only a rotation then the viewpoint, 1, and 2 should still >>be aligned and >>1 and 2 should then be seen at the same point. I verified this in OpenGL >>fine. >> >>The only way that I can explained this behavior is if the projection screen >>instead of the >>viewpoint was rotated. So do I miss something and I need to tune a parameter >>of the view >>platform or is the perspective model wrong? >> >>Any help would be appreciated >> >>Thanks >> >>Yohan Baillot >> =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JAVA3D-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
