I am writing code that lets a user draw a rectangle on the screen, then deletes everything within the rectangle. This rectangle will generate a frustum shape in the virtual world. Because I am surface rendering objects, I need to compute this frustum, because the user may delete half of an object, in which case I need to compute where the object was cut and generate some more surface mesh for the newly visible bits of the object. Does anyone have any suggestions how I can compute this frustum. As far as I can work out so far, I need to generate an edge of the frustum for each of the 4 points on the rectangle that the user selects. So, given a pixel location (x,y) on the canvas3D, I need to generate a ray pointing away from the screen, passing through all points that map to that particular (x,y) pixel location. Because of the perspective transformation, this ray will NOT be perpendicular to the image plate. Given the canvas3D, I can use: canvas.getPixelLocationInImagePlate(x,y, point) canvas.getImagePlateToVworld(trans); trans.transform(point); to translate from a pixel on the canvas3D to a point in the virtual world. But how do I find all the other virtual world co-ordinates that also map to this pixel (i.e. I've got a point on the frustum, but how do I work out the direction vector of the frustum edge)? thanks for your help Robert -- Robert McLaughlin Medical Vision Lab Department of Engineering Science University of Oxford =========================================================================== 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".
