Quote:Original post by Airo
I've got a question about Dimitry's matrix orthonormalizing method.

This way the same columns are used. Is it a good idea to switch the order for which columns are processed for the orthonormalization during the simulation?

first with the order dimitry gave and next orthonormalisation
for example start with Column3=Normalized(CrossProduct(Column1,Column2)) and do other 2 columns

or is this just making things more complicated?

It shouldn't matter -
Column1=Normalized(CrossProduct(Column2,Column3));
Column2=Normalized(CrossProduct(Column3,Column1));
needs to be normalized anyway.
Maybe my version is marginally more mathematically stable, but i can't say for sure.

It may be useful to swich order depending to what axis more needs to be keept mostly untouched.
It's may be better in some cases to keep specific row.
(it will work with rows instead of columsn as well). For instance, if matrix contains global->local transform for camera, iin opengl style, it's better to keep 3rd row.

interesting picture.

what is it? a vonoroi representation of the vertices of a subdivided isocahedron?

Quote:Original post by Eelco
interesting picture.

what is it? a vonoroi representation of the vertices of a subdivided isocahedron?

Yes,kinda like that.
Some more things
I'm using some kind of projection matrices to get coordinates on icosohedron faces - i just multiply coordinate with 3x3 matrix and then divide result by result's z, and i'm getting point projected onto icosohedron face.

sounds very interesting for planet rendering.

You two are hopeless.

Quote:
“1:Eelco gave keyword for search, therefore, he answered original question. I just failed to remember that it's named after Gramm-Schmidt, so i posted a solution.”

I am glad he is learning that method I was the want who introduced to him after hi gave another erroneous answer to similar question in another tread. But I think he still needs to understand the meaning of it and not applying it literally.
And not he did not answer the question he just say quaternion are better than matrices.
And that is not truth. Maybe for him they are.

Quote:
“2:It's not needed to rewrite everything, because quaternions and rotation-only matrices represent same thing. They both is concatenated by multiplication, both should have functions like "load to openGL", most methods of both is the same. With good design, it's not a problem to replace one by other. Also, it's probably better if OP will rewrite it now than later, because probably the only thing he need to rewrite now is camera class.”

You are totally wrong man quaternion do not concatenate by multiplication, I just proved to you, just do it yourself, before making such statements, and yes replacing the transformation in a major re-factoring job that may bring a whole new bag of bugs. It may not even be possible, as I read the person is using directx.

Quote:
“3:I don't think no one else understands rotations better than i. Yes, i sometimes have altitude like "f34r my math skillz", but it's usually when i'm first to reply with some simple calculations done in mind.”

Wow that is a strong statement, the only think I can say is that it speaks for itself.
Oh maybe you should do more things on paper and less work in your mind, you could get better result, and less misleading would result of such impulsive reactions.

Quote:
“In summary: If you need to store and process variable rotation, quaternions is better than matrices”

perhaps you should rephrase it like this:

If you need to store and process variable rotation, in my opinion quaternions is better than matrices”

As for Eelco: I think there is not point to continue this argument: Eelco I think you should use quaternion in your projects and do not let anyone else to convince you otherwise.

Bye.

Quote:Original post by Anonymous Poster
You two are hopeless.

Quote:
“1:Eelco gave keyword for search, therefore, he answered original question. I just failed to remember that it's named after Gramm-Schmidt, so i posted a solution.”

I am glad he is learning that method I was the want who introduced to him after hi gave another erroneous answer to similar question in another tread. But I think he still needs to understand the meaning of it and not applying it literally.
And not he did not answer the question he just say quaternion are better than matrices.
And that is not truth. Maybe for him they are.

ah that explains a lot. i thought i recognized that debating style, or rather lack of it, from somewhere.

Quote:
Quote:
“2:It's not needed to rewrite everything, because quaternions and rotation-only matrices represent same thing. They both is concatenated by multiplication, both should have functions like "load to openGL", most methods of both is the same. With good design, it's not a problem to replace one by other. Also, it's probably better if OP will rewrite it now than later, because probably the only thing he need to rewrite now is camera class.”

You are totally wrong man quaternion do not concatenate by multiplication, I just proved to you, just do it yourself, before making such statements, and yes replacing the transformation in a major re-factoring job that may bring a whole new bag of bugs. It may not even be possible, as I read the person is using directx.

why are directx and quaternions mutually exclusive? i dont know directx, so it might be for all i know, but it somehow seems very unlikely to me.

Quote:
Quote:
“3:I don't think no one else understands rotations better than i. Yes, i sometimes have altitude like "f34r my math skillz", but it's usually when i'm first to reply with some simple calculations done in mind.”

Wow that is a strong statement, the only think I can say is that it speaks for itself.
Oh maybe you should do more things on paper and less work in your mind, you could get better result, and less misleading would result of such impulsive reactions.

Quote:
“In summary: If you need to store and process variable rotation, quaternions is better than matrices”

perhaps you should rephrase it like this:

If you need to store and process variable rotation, in my opinion quaternions is better than matrices”

As for Eelco: I think there is not point to continue this argument: Eelco I think you should use quaternion in your projects and do not let anyone else to convince you otherwise.

Bye.

on the contrary. maybe this debate is pointless, and i fear it is, but if you would present some arguments as to why quaternions are not superior to matrices for the stated purposes, i would gladly consider them. unfortunatly, your ratio bewteen logical arguments and flames seems to be lowering by the post...

Just a note.
In algorithm that i posted before, not used SQRT routine.

When you do cross and normalization , you use SQRT or invSQRT.

Quote:Original post by Anonymous Poster
You two are hopeless.

Quote:
“1:Eelco gave keyword for search, therefore, he answered original question. I just failed to remember that it's named after Gramm-Schmidt, so i posted a solution.”


I am glad he is learning that method I was the want who introduced to him after hi gave another erroneous answer to similar question in another tread.

Do you realize that it's not a valid argument?

Quote:

But I think he still needs to understand the meaning of it and not applying it literally.
And not he did not answer the question he just say quaternion are better than matrices.
And that is not truth. Maybe for him they are.

Quote:
“2:It's not needed to rewrite everything, because quaternions and rotation-only matrices represent same thing. They both is concatenated by multiplication, both should have functions like "load to openGL", most methods of both is the same. With good design, it's not a problem to replace one by other. Also, it's probably better if OP will rewrite it now than later, because probably the only thing he need to rewrite now is camera class.”

You are totally wrong man quaternion do not concatenate by multiplication, I just proved to you, just do it yourself, before making such statements,

Where you proved? Proved what?

Read the <href="http://www.flipcode.com/documents/matrfaq.html">FAQ
or gamedev version

and mathworld, look at end of page.

Quaternion rotations is concatenated by quaternion multiplication.

Quote:
and yes replacing the transformation in a major re-factoring job that may bring a whole new bag of bugs. It may not even be possible, as I read the person is using directx.

First time hear that quaternions is inpossible in directx.... interesting.

Quote:
Quote:
“3:I don't think no one else understands rotations better than i. Yes, i sometimes have altitude like "f34r my math skillz", but it's usually when i'm first to reply with some simple calculations done in mind.”

Wow that is a strong statement, the only think I can say is that it speaks for itself.
Oh maybe you should do more things on paper and less work in your mind, you could get better result, and less misleading would result of such impulsive reactions.

Maybe i have incorrectly computed angles and axises of your example quaternions?
Please catch at least one formal mistake i made in calculations before suggesting me what to do in paper.

Quote:

Quote:
“In summary: If you need to store and process variable rotation, quaternions is better than matrices”

perhaps you should rephrase it like this:

If you need to store and process variable rotation, in my opinion quaternions is better than matrices”

As for Eelco: I think there is not point to continue this argument: Eelco I think you should use quaternion in your projects and do not let anyone else to convince you otherwise.

Bye.

Bye.

[edit: quote tags fixed]

[Edited by - Dmytry on October 26, 2004 1:56:12 PM]

Quote:Original post by minorlogic
Just a note.
In algorithm that i posted before, not used SQRT routine.

When you do cross and normalization , you use SQRT or invSQRT.

Ya gde-to pro eto chital dage, vozmozhno tvoi tekst. Eto ti pridumal pervii? (moy quaternion-to-matrix prosto delaet mashtabiruuschuu matricu esli quaternion ne edinichnoi dlini). Mozhno novuu temu zapostit' , a-to tut opyat' anonimi vodu mutyat (delo konchitsya tem chto voobche zapretyat anonimov nafig). Eto osnovanno na idee chto esli podelit matricu na dlinu v kvadrate, poluchim pravilnuu matricu?

Yes, i readed about it somewhere. Maybe it was your text. It's interesting. It uses idea that if we scale resulting matrix by 1/squared_quaternion_length, we get matrix without scaling?

2everyone logged in: what you think about this quaternion from matrix and quaternion to matrix formules? Is it's known?