Hi Guy, Have you trying used osg::AutoTransform?
Also osg::Camera allows you to disable clear of the either the depth or colour buffer. See osghud example. Robert. On Tue, Mar 17, 2009 at 6:14 AM, Guy <[email protected]> wrote: > > Hi, > What I'm trying to accomplish is to draw a given pattern instead of the > projected object, on special condition. That pattern is no longer > 3DWorld oriented, but instead, screen pixels oriented, with the > exception of keeping the 3D distance of the 3DWorld object. > > Suppose I have a model of a 3D house and a model of a truck, and the > condition is "The truck is more than 300 feet from the house", then when > the condition is true, instead of drawing the truck, I want the pixel > (30,35) to be drawn blue and pixel (78,90) to be drawn green. > > The important thing is that if the truck ZBuffer value was 'Z' I want > pixels ZBuffer value to be the same 'Z', now since the truck has many > vertices and therefore many 'Z's I only refer to the 'Z' of the middle > of the truck bounding sphere. > > I hope it makes more sense now... > > I forgot to mention that in osg1.2 instead of 'Camera' for the > orthographic projection I used 'osg::Projection' which as far as I > understand only changes the projection-view matrices and doesn't harm > the Z buffer, but the pixels were drawn above all other objects. > > I also 4got to mention that in osg2.8 and the Camera, I tried to render > it PRE_ORDER, IN_ORDER and POST_ORDER with no different results. > > I never used the stencil buffer for anything but if I understand > correctly it just prevents masked pattern on the viewport from being > drawn, which is not my goal. Anyway, I'm going to read about stencil in > the Red book. It wouldn't hurt. :) > > Thanks, > Guy. > > >I'm not sure I entirely understand what you're trying to accomplish, > but > >perhaps you want to look into using a stencil buffer and/or pixel > shader > >to control what gets rendered? > > Guy wrote: > > > > Hello, > > > > > > > > I'm trying to merge two sub-graphs to the same image. It doesn't work > > > so well, so I'll try to explain what in general I'm trying to achieve, > > > then my not working so well solutions, and then the questions J > > > > > > > > So, in general I want to replace an object (A) in the scene with > > another object (B) on some condition. The object (B) is some pixels > > which are lit up. The important thing is to keep the 3D scene distance > > > from the camera for both objects, so if the object is obscured by > > another, then both (A) and (B) will be obscured, and if some other > > object (C) is obscured by (A), it will still be obscured by (B). > > Object (B) might be partially transparent. > > > > > > > > Not working so well solution 1: > > > > Have switch for (A)/(B). > > > > The position of (A) is multiplied by view-projection matrix, the > > result is pos'. (B) is a set of points which their vertices are pos' > > with (x,y) replaced by the pixels I want to lit, and the new positions > > > are multiplied by the inverse-projection invers-view matrices. > > > > This solution had problems with setting the right pixels. > > > > > > > > Not working so well solution 2: > > > > Object (B) is a set of pixel under ABSOLUTE_REF orthographic > > projection with (x,y) of the pixels I want to lit and z is the > > negative distance between (A) and the camera. > > > > This solution has the correct pattern of the lit pixels, but the Z > > order doesn't seems to be correct. > > > > > > > > The implementation of solution 2 is to add camera with ABSOLUTE_RF and > > > orthographic projection. View is identity. I set the clear mask to 0 > > since I don't want the Z-Buffer to be cleared. (opposed to huds and > > that kind of implementations). > > > > > > > > I used the osgviewer to put the cow at 0,0,-300 under absolute_rf, and > > > a point at 0,0,0 under separate camera with orthographic projection, > > and the point was hidden by the cow (which is a mistake). > > > > I thought that I might need to set the zNear/zFar of both camera's to > > be the same, but in this simple example it shouldn't matter since the > > point Z is zero... > > > > > > > > So first, do I have to set the zNear/zFar of both camera's to be the > same? > > > > > > > > Any ideas whats going wrong? > > > > > > > > Other solutions for the problem? > > > > > > > > Btw, I tried to replace the points by quads under orthographic > > projection. The results were the same. > > > > > > > > Thanks, > > > > Guy. > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >
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