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apatriarca

Member Since 03 Jul 2006
Offline Last Active Today, 11:43 AM

Posts I've Made

In Topic: Matrix right hand to left hand problem

04 December 2014 - 10:03 AM

You also have to flip the order of all multiplications. In fact, (A*B)^T = B^T * A^T != A^T * B^T.

In Topic: find components distances from 2 points on a plane n

25 November 2014 - 09:21 AM

You have to define a coordinate frame on the plane. Both the distances along these coordinates and the angle depends on this arbitrary choice.

In Topic: Find a two points in differents segments which their distances is K

20 November 2014 - 11:25 AM

The two points you have written are not the unique points satisfying your condition. Your two segments are defined by the equations

P(t) = (1 - t)A_0 + tA_1, Q(u) = (1 - u)B_0 + uB_1 (0 <= t, u <= 1).

You want to find all the values of t and u such that the equation (P(t) - Q(u))^2 = k^2. This is a quadratic equation in two variables and the solution is thus not necessarily unique. Is there any other restriction you have in mind? Do you want the two points to have the same x-coordinate?

In Topic: Is upper division Linear Algebra a good idea or necessary?

06 October 2014 - 01:49 AM

In Opengl, the operation is component wise multiply, though it has no sence to be used in manner of geomteric need, it ields a vector space where column and row vectors are the same, implying certain inpropriatness of talking about transposing a matrix, since it transposes by its order with multiply operation (that is impossible in linear algebra becouse of NxM demand in mutipling matricies/vectors, implying also vectors to be nx1x1xm, but that algebra has its definition of operation, that opengl does differ in (it will multiply vectors without their dimension introduced), thus opengl has a vector space of different properties- where multiplication is not associative- but it is a vector space).

OpenGL uses the same data type for several different things, not just geometric vectors. In particular, it uses them for colors. The component-wise multiplication is in fact very useful in this case. Code implementations of mathematical concepts are rarely completely equivalent to their theoretical version.

In Topic: OIT (Order Independent Transparency)

17 September 2014 - 10:10 AM

The Intel solution is based on a quite recent and, as far as I know, Intel-only extension. The Weighted Blended OIT is more general, but it is an approximation. There are also other methods (A-buffers for example). I don't think this is a solved problem and in many cases sorting is still probably the way to go. The best method depends on what you are trying to do and the scene you are trying to display.


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