View Full Version : Matrice Transformations

Cairn

05-10-2010, 07:29 PM

Hey I've been using OpenGL for a little while now and even though i know how to use matrices i don't fully understand them I understand how translations and scaling works but how does sheering shift individual vertices does it shift above an axis or what Ive spent hours looking for a solution and i just cant seem to find one and another question is when multiplying a matrix with MultMatrix(Matrix) does it multiply against a 4x4 matrices or one like this

[ x ]

[ y ]

[ z ]

[ w ]

and if i don't know the slightest about what I'm talking about please put me on the right track.

Rosario Leonardi

05-11-2010, 01:23 AM

Let's make it simple and let's try with a 2x2 example.

If you have a shearing matrix like that

| 1 a | |x|

| 0 1 | * |y|

the final point became

x' = x + a*y

y' = y

The shearing matrix move a vertex on a axis in a proportional way to another axis.

| 1 0 0 0 | |x|

| 0 1 a 0 | * |y|

| 0 0 1 0 | * |z|

| 0 0 0 1 | * |w|

In this 4x4 matrix the y change proportional to the z (if a is not zero), all the other variable are unchanged.

x' = x

y' = y+a*z

z' = z

w' = w

Cairn

05-11-2010, 12:00 PM

But does that apply to all vertices and if it does doesnt it just shift all the vertices up(or down) or does that shift an individual vertice.

ZbuffeR

05-11-2010, 02:03 PM

y' = y+a*z

Well it will shift "a times z" the y component of each vertex.

So vertices with higher z will shift more. That is all.

Cairn

05-11-2010, 02:19 PM

ooooohhhhhhhhhhhhh!!!

yes thank you.

thank you

it just popped oh yes you dont know how happy youve made me.

you just made my day thanks again.

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