Thanks Marcus,
what if I scale the images first, and then render them as foreground?
2009/8/10 Marcus Lindblom <[email protected]>
> Jie Liu wrote:
> > Hi,
> >
> > I want to use OpenSG do display about 150 images located in a given
> > directory.
> > For each time, I show one of them, and I press left key or right key to
> > nevigate backward or forward. All images should align center, keep their
> > width/height (w/h) ratio and they will fit to the width or height of the
> > window according to the value of w/h ratio.
> >
> > I now have three solutions for this purpose.
> > a). take an image as a background object. The problem is OpenSG will
> > auto scale the image to the window area for me. But as I must keep the
> > width/height ratio of the image, I give up.
>
> That's just how the default ImageBackground works currently. Adding
> aspect-keeping functionality would be a welcome patch though. :)
>
> > b). take an image as a foreground object, the problem is I can only
> > appoint its bottom-left position. There seems no parameters for me to
> > scale its size.
>
> IIRC, I'm not sure OpenGL can scale images uploaded with glWritePixels,
> so that would be OpenGL's fault, not OpenSG's. :)
>
> > Below are my code to do this
> > ===================================================================
> > ImagePtr tImage = Image::create();
> > *tImage->read(file_name[index]);* *// I change the value of /index/
> > to display different images. Images are loaded dynamically according to
> > their names*
> >
> > ImageForegroundPtr ptrImgForeground = ImageForeground::create();
> > beginEditCP(ptrImgForeground);
> > {
> > * ptrImgForeground->addImage(tImage, Pnt2f(0.0, 0)); // Can I
> > assign a bounding box for an image? Or do I have to manually scale the
> > image first?*
> > }
> > endEditCP(ptrImgForeground);
> >
> > * g_ptrViewport->getMFForegrounds()->push_back(ptrImgForeground); *
> > *// push_back is to add a new image to the queue, OpenSG will try to
> > render all images in the queue and this will slow down the rendering
> > speed obviously. But I only want to display a single image at one time.
> > So what is the right and efficient way to replace the current foreground
> > image?
>
> g_ptrViewport->getMFForegrounds()[0] = ptrImgForeground;
>
> > *================================================================
> >
> > c). Take an image as a texture material, and attach it to a Quad
> primitive.
> > ================================================================
> > ImagePtr tImage = Image::create();
> > tImage->read(file_name[index]);
> >
> > beginEditCP(g_ptrGeoTex);
> > g_ptrGeoTex->setImage(tImage); *// g_ptrGeoTex is a globle variable,
> > its type is SimpleTexturedMaterialPtr*
> > endEditCP(g_ptrGeoTex);
> >
> > beginEditCP(g_ptrGeoQuad);
> > g_ptrGeoQuad->setMaterial(g_ptrGeoTex);* // I found the
> > setMaterial process will be very very slow, how can I accelerate it?*
>
> You're probably suffering from auto mipmap generation here. (Mipmapping
> for textures is enabled by default, and if you set an image with no
> mipmaps, OpenSG creates them for you whe you use the material for the
> first time). Try setting the minification filter (minFilter) to GL_LINEAR.
>
> > endEditCP(g_ptrGeoQuad);
> > ================================================================
> >
> > So, what is your suggestion to write such a program?
>
> If you have enough memory (system and gfx) textures is probably the way
> to go, because you can do more fun stuff with them (animation etc).
>
> If not, you probably need to use ImageBackground or ImageForeground, but
> neither of these do what you want currently, so you need to hack them a
> bit. If you know OpenGL well enough to do get it to do what you want,
> this is pretty easy. (I haven't looked at that part of OpenGL for a
> time, so I can't say if nor how it can and should be done. Maybe some
> other guys know better).
>
> > I also want to load
> > all iamges at the begining of the program and store them in vectors
> > (vector<ImagePtr>, and vector<SimpleTexturedMaterialPtr>), but the
> > program crashed while switching the image. What is the right way to read
> > and store all image data?
>
> You probably want Image|MaterialRefPtr to make sure your images stay in
> memory here. However, make sure your images fit in graphics memory if
> you use textures.
>
> > The email is a little long, I hope it will not bother you too much~
>
> Not at all. Glad to help. :)
>
> Cheers,
> /Marcus
>
>
>
>
>
>
>
>
>
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--
Jie Liu
Visualization Research Group
Center for Information Science, School of EECS,
Room 2104, Science Building No.2,
Peking University, Beijing 100871, China
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