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legends2k

Member Since 15 May 2012
Offline Last Active Aug 17 2015 03:35 AM

Posts I've Made

In Topic: Disassembly and assembly links

14 July 2015 - 03:43 AM

An older Wayback machine snapshot had the images. I rsync'd the complete tutorial (12 parts with text and images); made an offline archive stripping off irrelevant parts.

 

The last two parts has sample code that could be downloaded but I couldn't recover them. Asked the author, he too didn't have backups, but for all the other parts the code is part of the tutorial/image, no a separate downloads, so it isn't much we're missing.

 

The download link, with the author's permission.


In Topic: When/where does handedness really matter?

12 March 2013 - 07:38 PM

Never. In both cases the vector mathematics is the same. The only difference is that in a right handed system it will be on the right hand side of the origin, and in a left handed system it will be on the other side.

Oh good, because this is exactly what I was thinking when I revisited cross product definition; although handedness decides the direction of the resultant of the cross when it boils down to math, the formulas don't change, numbers are still numbers, the resulting numbers would be the same; it's humans who interpret it based on the coordinate system handedness based on our liking.

Now, if you happen to be using either system, and introduce a scaling of -1 in one of the axes, then your coordinate-frame will now be the opposite handedness to your coordinate-system. I suspect that's what the author of the book was attempting to explain.

Yeah, in the reference of one system, when a new one is introduced via mirroring then this test would help.

Thanks!

In Topic: When/where does handedness really matter?

12 March 2013 - 01:16 PM

I'm now clear of the part that a model/asset by itself isn't explicitly left or right handed while to see it exactly the way its creator expected it to be seen, we need to interpret in that system.

However, I'm reading "Essential Mathematics for Game Programmers", in which there is a statement which goes, "when we've three basis vectors i, j and k, performing scalar triple product like (i x j) . k > 0 then it is right handed while if it's negative it's left handed".

What confuses me is, I took 3 vectors say 1i, 3j, 4k and drew them both in a left and right handed system, perform the aforementioned scalar triple product, I always get 12, which is positive, when would this be negative to show that the basis is left handed?

In Topic: When/where does handedness really matter?

12 March 2013 - 01:30 AM

Well if your projection matrix and view matrix are set up for a left-handed coordinate system, then if you interpret the data in a resource file as right-handed, and attempt to render them, everything will be on its side and backwards (from the point of view of humans looking through a monitor) smile.png

 

Agreed. My point is how do you differentiate a LHS model and RHS model, what exactly is different between the two? The reason I'm not able to differentiate is that both models will've just numbers; say in a triangle of vertices v0 (0, 0, 0), v1 (0, 0, 1), v2 (1, 0, 1) where's the handedness encoded/lurking?

 

Similarly, given three vectors say i (1, 0, 0), j (0, 1, 0), k (0, 0, 1), how do you know if it's left or right handed. In my first post, I'd quoted

 

 

you can test the "handedness" of a coordinate
system given the basis {v1, v2, v3}.

if (v1 x v2) . v3 > 0, then it''s right-handed.
if (v1 x v2) . v3 < 0, then it''s left-handed

 

But then with the above vectors, considering them as either left or right both pass the test. Then how do I differentiate?


In Topic: Can't decide which math/physics basics book to get

12 March 2013 - 01:25 AM

Essential Mathematics for Games and Interactive Applications

Seems appropriate for my level
Seems to use proper terminology
Does not cover trigonometry or calculus, doesn't even include a reference of the trigonometric identities

 

Nope, I've this book, in the disc provided with it, you've 4 appendices. Perhaps you didn't look at the TOC properly.

Appendix A - Trigonometry

Appendix B - Calculus

Appendix C - Coordinate Systems
Appendix D - Taylor series

 

My review of the book is that it covers the basics extremely well, the authors seem to be very sincere in what they did, giving so much of attention to detail. I've come up till Chapter 6, and so far so good!


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