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Member Since 18 Dec 2006
Offline Last Active Nov 20 2013 09:14 AM

Posts I've Made

In Topic: Shadow mapping depth buffer resolution problem

22 October 2013 - 08:12 AM

Hi guys, thanks again for feedback!


The actual problem I am trying to solve is to make a visibility map for line of sight. Basically you have an observer which can be dragged about on a 2D map and you want all the areas that are visible from the observer's position to be visualized.


In the following screen shot you can see one example where it works more or less as planned with the observer on a mountain, The green areas are visible, while the red are invisible.


Attached File  LineOfSight.png   392.66KB   3 downloads


In the next shot, I have placed the observer 5 meters above the sea.


Attached File  LineOfSight2.png   31.38KB   4 downloads


Here you can see we get a cutoff at a couple of kilometers distance. I suspect this is due to the depth map resolution as described in the original post. Another effect I don't understand is the peculiar "pillow" shape of the visibility map. This shape only appears when I account for the earth's curvature in the calculations, but I can't see why it should be shaped like this, it should be circular and further out from the observer. If I do not account for earth's curvature, the shape is more square.


I have tried with non-square projection matrices. The results are much better when I reduce the vertical FOV, but I still don't get the full range, even with the FOV at 5 degrees.


I don't think cascading shadow maps would help in this case. IIRC, in CSM you split the view frustum and make one shadow map for each, section along the distance of the view, but in this case I would be more interested in splitting the light frustum.



In Topic: Shadow mapping depth buffer resolution problem

18 October 2013 - 03:06 AM

Hi and thanks for the answer :-) I don't think the z value distribution is the problem here, I'm currently using logarithmic depth values which is supposed to increase the precision on the far values.


The problem here is rather that the y values map to the same pixel in the depth map, and of course only the closest one is stored.

In Topic: Simple water rendering from various altitudes

25 November 2009 - 03:05 AM

Original post by swiftcoder
Original post by tseval
Now, one challenge here is that the water should look nice from a large span of altitudes, ie. it should look nice from a fairly close distance (walking along the water shore) as well as when flying 10km above the water. Using a simple tiling noise texture may look good very close up, but when zooming out, the repeating tiling pattern will be noticable, as well as the high frequency of the noise gets very disturbing.
If you ever look out the window of an airplane, you will notice that the ocean *does* look a bit odd due to the high-frequency noise of the waves. I think the key here is to reduce the surface opacity with altitude, which will also reduce the intensity of surface noise.

True, I'm still not sure how to reduce the tile patterns in the noise though. Any ideas?

In Topic: Incomplete render buffer for depth texture

07 September 2009 - 01:03 AM

Great! That solved it, thanks a lot :-D

In Topic: Handling huge depth range spans

20 August 2009 - 09:37 PM

Great, thanks! I'll check it out