Rendering an element outside the frustum ?

vimes · Post by **vimes** » Fri May 19, 2006 5:23 am

Hi all,
I'm currently working on displaying a planet covered with meshes representing cities. The camera view point is always looking at the "core" of the planet which is located at the origin.Thus there is always a dark side of the planet containing cities which doesn't need to be rendered.

Currently, I am setting the camera far clip distance to the distance between the camera and the origin. The problem is that the sun rotating around the planet is never rendered because always outside of the frustum...

so, is there any way to make that single element outside the frustum to be rendered ? I tried to find a way to detach the bouding box from the graphical element and relocate it within the frustum but I couldn't find one..

Thanks in advance for your help!

ColinDoody · Post by **ColinDoody** » Fri May 19, 2006 5:42 am

vimes- i have no idea how to specifically do this in ogre, as I have not programmed enough ogre, but I do think this is an interesting issue and would like to analyze it based on my personal, limited knowledge.

The one thing I can relate it to somewhat is skybox in Valve's HalfLife 2 engine . In halflife, there are "buildings" rendered that appear to be far away. Despite the far clip distance, I believe they always render. That is because they are not actually far away; they are rendered through a smaller model where the skybox is not just a sequence of images but a camera pointed at that model.

Maybe Im not making sense, and obviously HL2s occlusion techniques were far more advanced than a far clip plane , but maybe the solution lies in doing some sort of similar technique? Making the skybox link to some sort of camera and then have the sun rotate around that in sub-model. Skyboxes always render ...

... ... Im not sure- interesting question. Id like to hear the answer from someone who knows what they are talking about.