# Xashmi

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1. ## [DX9] Point inside pyramid

This line [source lang="java"] D3DXPlaneFromPointNormal(&plane, &lightPos, &vPyramidLightNormals);[/source] Here you should use one of the points in the pyramid corresponding to the normal instead of lightPos. Unless you need the normals for anything else I think you'd be better off if you just computed the plane directly. Instead of your "GetTriNormal", use a "GetTriPlane".
2. ## Applying Force in the most basic way....

Using a force to simulate impacts between two hard objects is not numerically stable. You'd have to use an extremely small timestep so that the 'hard' collision becomes 'soft'. You could make it work by isolating a single impact and integrating only this impact in detail with a very small timestep. In practice it is much easier to use the impulse or conservation of momentum.
3. ## Convert vector to tangent space

This looks wrong: [source lang="c"]lightDistanceOut.w = ZERO_VECTOR;[/source] Assuming w is a scalar component should not this be [source lang="c"]lightDistanceOut.w = 0.0;[/source] alternatively [source lang="c"]lightDistanceOut = ZERO_VECTOR;[/source] ?
4. ## Using partial derivatives to light circular waves

An artifact from using higher wave numbers than can be represented by the mesh perhaps?
5. ## Life on mars, yes or no and why so?

This depends on a common interest in a type of resource. What could an advanced group want from earth that it would not easily get elsewhere? Minerals or compounds? Unlikely - just nothing too special here (and why use energy lifting it out from the gravity well of a planet when you can mine asteriods). A planet to live on perhaps? Also unlikely I think. We are already starting to observe extrasolar planets and it looks quite likely that there are a lot of earth like planets out there (unless they are already taken ;) ).
6. ## Another Bezier path question

As TheUnbeliever says, you need to carry over a fraction of the increment to the next curve. Say you increment by 0.3, then the T values for your first curve will be 0, 0.3, 0.6, and 0.9. The second will be 0.2, 0.5, and 0.8. The third 0.1, 0.4, 0.7 and so on. A simple formula would be T = T_global - floor(T_global); Where you increment T_global instead of T, just remember to keep track of which curve you are on.
7. ## Null space of a matrix

I'm not an expert but according to wikipedia it looks like singular value decomposition is your best bet (if you want a numerically accurate algorithm). As it happens, there are no exact algorithms to compute the SVD though, instead you have to use an iterative approach. LAPACK provides routines to compute the SVD and I suggest using them instead of implementing your own (unless you want to do it for educational purposes).
8. ## Life on mars, yes or no and why so?

Burning hydrogen does not emit CO2, but making it does. So does just about all kinds manufacturing. But in global perspective, space exploration is a fart in a pig farm. Ultimately, humanity has to choose between expanding into space or become extinct. The earth will not habitable in 3-4 billion years from now if we dont advance technologically (which space exploration is an example of). Sure, everyone living now will be dead by then, but most of us will not live long enough to be affected by global warming either. By the way, chinese government is not stupid. Their main concern is energy crisis though, not global warming. Which is why they invest more than the US in renewable energy (at least they did a year back or so).
9. ## Life on mars, yes or no and why so?

Curiosity is landing in a month. Maybe we will find out. Anyway, here is an opportunity to come with your best guess. Myself: Yes Why? Two reasons. 1) There are microorganisms on earth that could survive on mars. 2) Every once in a while asteriod impacts causes a small exchange of matter between planets. Over millions of years chances are that some robust microorganisms could have survived the trip from earth to mars.
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