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# JohnnyLightwave

Member Since 11 Jul 2011
Offline Last Active Oct 07 2015 06:31 PM

### In Topic: Getting the extends of a plane intersection the view frustrum

27 July 2015 - 08:36 AM

Hi IYP,

Thanks for the terrifying equation help!

I define my planes like this:

```//
// Plane
//
class Plane
{
Vector		mPos;
Vector		mNormal;
float		mD;

void Create(Vector thePoint, Vector theNormal)
{
mPos=thePoint;
mNormal=theNormal;
mD=-theNormal.Dot(thePoint);
}
};

//
// Frustrum
//
enum
{
FRUSTRUM_RIGHT=0,
FRUSTRUM_LEFT,
FRUSTRUM_TOP,
FRUSTRUM_BOTTOM,
FRUSTRUM_NEAR,
FRUSTRUM_FAR
};
class Frustrum
{
Plane					mPlane[6];
};
```

So essentially my frustrum is just a bunch of planes cutting into eachother.  While I'm good with 2D, I have trouble conceptually adding that third dimension into equations (I do 2D geometry native, but am just an idiot savant in 3d), so I'm a little unsure how I would extract L1 and L2 from my set of six planes (except via a brute force method that would do the trick but probably is optimized away by pure math).

Do you think you could give me a suggestion on how to extract from these classes into the variables to plug into your dread equation of darkness?

Thanks!

### In Topic: Circle embedded in line-- fastest vector to unembed

20 May 2015 - 01:45 PM

however, we are talking about a fraction of a second, over a million iterations to see such differences, and at the cost of a minor bit of accuracy. i still think overall 1/sqrt is much simplier than this other method.

Yeah, that's not enough to matter for my purposes.  It's more that I was wondering if there was some completely alternate way of doing it that I might be missing out on-- you know, like all those nice tricks you can do with dot and cross products.

For my specific purposes-- direction toward/away from infinite line from a particular point, I hoped their might be some common equation that I was ignorant of, rather than "find closest point, normalize vector."  That WORKS, but again, sometimes there's cute tricks, and that's what I was hoping for.

### In Topic: Circle embedded in line-- fastest vector to unembed

20 May 2015 - 06:21 AM

♬♬ Every cycle's sacred... every cycle's good... every cycle's wanted, in my neighborhood... ♬

However, I don't need it PERFECTLY normalized... I just need it pretty close to one.  I wonder what tricks I can do by multiplying my vectors by huge numbers, so they approach infinity, and then divide them by eachother.  That might work for my resolution.

### In Topic: Circle embedded in line-- fastest vector to unembed

20 May 2015 - 04:16 AM

Sadly, that's pretty close to what I have.  I was hoping there was some method of figuring it out without that "normalize."  I'm using this to potentially, at worst case, unembed a whole lot of things, so I want it to be as efficient as possible, and without sqrt.

### In Topic: Box-- Absorbing impulse after collide

10 May 2015 - 11:20 AM

A final update... it appears this problem cannot be solved simulaneously... or the solution is more than a quick velocity mod can handle.  I started another thread, showing all the conditions that work, and the one condition where it fails: http://www.gamedev.net/topic/668296-collisionunembeddingpushing-and-a-seemingly-impossible-case/

If you're interested in following up, click over there... this has become somewhat of a quest to me now, and I'm actually writing a small, shallow simulator because I'm now interested in the mechanics philosophically rather than just practically.

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