BSP tree for occlusion ++
Author
I know there is lots of threads here about BSP I even see one 7 threads furuther down here. But I just need a some simple hints here..:)
I am writing a simple indoor 3D engine just for fun in C# and GDI+, and I need to first find out what walls not to draw, then to draw them back to forth. I know how to set up a BSP tree and traverse it to draw from the back to the front, but how do I find out what walls are outside my FOV? Behind me or to the left or what ever? Is that what they call painters algorithm (ftp://ftp.sgi.com/other/bspfaq/faq/bspfaq.html#9.txt)? Or is that something else? If it is, is it a good way to do it, or is there an other way you would recomend for me to take away walls from my rendering queue?
Thanks
BugSlayer
Culling -- if all the vertexes of the view frustum are on one side of the plane of a node, then the other side of the node is not in the view frustum and does not need to be drawn.
Painter's Algorithm -- this is a method of drawing polygons (back-to-front) so that they are properly obscured. Using a Z-buffer makes this unnecessary (except for polygons with transparency). In fact, when using a Z-buffer on modern hardware, polygons should be drawn front-to-back to take advantage of special hardware that rejects obscured pixels early in the pipeline.
Painter's Algorithm -- this is a method of drawing polygons (back-to-front) so that they are properly obscured. Using a Z-buffer makes this unnecessary (except for polygons with transparency). In fact, when using a Z-buffer on modern hardware, polygons should be drawn front-to-back to take advantage of special hardware that rejects obscured pixels early in the pipeline.
Quote:Original post by JohnBolton
Painter's Algorithm -- this is a method of drawing polygons (back-to-front) so that they are properly obscured. Using a Z-buffer makes this unnecessary (except for polygons with transparency). In fact, when using a Z-buffer on modern hardware, polygons should be drawn front-to-back to take advantage of special hardware that rejects obscured pixels early in the pipeline.
OK, thanks, don't think I will implement a Z-buffer right away, so will draw it back to front, and hope that it won't be too slow.
Quote:Original post by JohnBolton
Culling -- if all the vertexes of the view frustum are on one side of the plane of a node, then the other side of the node is not in the view frustum and does not need to be drawn.
Can you elaborate a bit more on that? When you saw ALL the vertices of the view frustum, do you mean the 4 vertices for the near plane, and the 4 for the far plane, so in total all 8 of them?
And what do you mean by "plane of a node". A node is a wall? and the plane is the red line on this picture for the "node" C?
And what do you mean by "then the other side of the node is not in the view frustum", do you talk about the "left" and "right" leaf in the binary tree. So if all the vertices is on the left side, then discard the right leaf and all its childs?
Thanks a bunch, really appreciate if you help me out with this.
- ØØ -
Author
Ehhh...sorry, that was me posting..didn't know I could post anonymesly...hmm....
BugSlayer.
BugSlayer.
Quote:Original post by Anonymous Poster
And what do you mean by "then the other side of the node is not in the view frustum", do you talk about the "left" and "right" leaf in the binary tree. So if all the vertices is on the left side, then discard the right leaf and all its childs?
Yes. That's it. One comment about terminology -- a leaf is a node that has no children.
Author
OK, thanks a bunch. English is not my first langauge, so sorry for the mix up with leaf. Will try to remember that next time.
Thanks a lot
- BugSlayer -
Thanks a lot
- BugSlayer -
Author
I have one/two more questions about this, so sorry for bumping this thread.
But the Binary tree. Is it only constructed ONCE the first time when you load the level, and after that it will never get altered? Because walls never move? And we are talking world coordinates here right?
- BS -
But the Binary tree. Is it only constructed ONCE the first time when you load the level, and after that it will never get altered? Because walls never move? And we are talking world coordinates here right?
- BS -
yes you build in world coordinates and yes the tree is built only once for stationary objects. the bsp tree arranges objects "realative" to one another, not to any specific world space point. thus if the relative position of the objects doesn't change, there is no need for the bsptree to change.
Tim
Tim
Author
Thanks, I kind of got what you ment by "relatively to each other". Because they are kind of dependent on each other. The world coordinates will tell you if one object is in front or back or left or right of an other object, hence also relatively.
Yeah, you know what I mean...hmm...so I think I got you. Will give it a shot and see what I can pull off.
Thanks
- BS -
Yeah, you know what I mean...hmm...so I think I got you. Will give it a shot and see what I can pull off.
Thanks
- BS -
Author
Ooops, one more question.
I can use an AVL tree right? I guess that won't mess up anyting? At least I guess it will give me an overall better performance, since all the balancing will be done at load time.
I can use an AVL tree right? I guess that won't mess up anyting? At least I guess it will give me an overall better performance, since all the balancing will be done at load time.
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