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# A9876

Member Since 12 Jun 2012
Offline Last Active Jun 19 2012 01:02 AM

### In Topic: how to draw threat dome

19 June 2012 - 01:05 AM

If I understand correctly what you want, this is all but trivial.

You basically want to construct a dome from the visible horizon from some arbitrary point. This is easy if you know the horizon (just extrude towards +Z and scale, repeat a few times, and there's your dome), but finding the horizon line is not easy.

Assuming a heightmap terrain (you didn't specify, but otherwise it is still a lot harder!) this means you have to ray-march over the terrain heightmap up to a maximum viewing distance and ignore everything that is less than your maximum value (because something that is below a higher elevation won't be visible). So basically, you only ever care about values that are higher than any ones (including the point you're standing on) you've seen before. Anything less isn't visible as long as the terrain isn't transparent and doesn't have holes. Eventually you will have reached a maximum distance (either practical because it's no longer of interest, or for effects like atmospheric attenuation, earth curvature, etc.).

Do that for, say, a dozen cardinal directions. This is a very coarse approximation. If the terrain between two rays is sufficiently "similar", your estimate is good, the distance that you find on two sibling rays is identical or more or less the same. If it is not, then your estimate is not accurate, so shoot another ray at the half angle between the two, repeating this recursively until you are happy with the accuracy.

Thank You...

### In Topic: how to draw threat dome

18 June 2012 - 06:23 AM

A9876

### In Topic: how to draw threat dome

18 June 2012 - 04:10 AM

A9876

### In Topic: how to draw lines over the terrain

13 June 2012 - 02:40 AM

Is Ztest is DEPTH_TEST? if yes i don't want see the lines behind a mountain.it should be over the terrain like flow path.

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