by DeadHamste » Tue, 10 Dec 2002 11:28:12
-DH
by PC Joh » Tue, 10 Dec 2002 23:37:38
> -DH
by Jukka Liimatt » Wed, 11 Dec 2002 03:31:45
Actually the vertices are defined in world coordinates, and the matrix tellsQuote:> I have written a 3ds file reader for use in my game. I have run into a
bit
> of an issue it seems. The 3ds file does not store world corrdinates for
> each mesh, instead it stores a 4x3 matrix for each mesh, and the vertices
> are based on that. I would like to know how to apply this matrix to each
> vertex in code, so that I can store the world coordinates instead of the
> modified ones. Does anyone have experience with this?
Last but not least, there is offset (=pivot) transformation which is applied
before drawing the node, but is not inherited.
So ; if you don't care about hierarchy or animation, you can simply draw in
world coordinates.
by DeadHamste » Wed, 11 Dec 2002 06:16:04
-DH
Quote:> > I have written a 3ds file reader for use in my game. I have run into a
> bit
> > of an issue it seems. The 3ds file does not store world corrdinates for
> > each mesh, instead it stores a 4x3 matrix for each mesh, and the
vertices
> > are based on that. I would like to know how to apply this matrix to
each
> > vertex in code, so that I can store the world coordinates instead of the
> > modified ones. Does anyone have experience with this?
> Actually the vertices are defined in world coordinates, and the matrix
tells
> what the matrix was. If you want to define the vertices in model
> coordinates, you have to multiply'em by inverse of the 4x3 matrix. You
need
> to do this if you want to begin to apply the animation/keyframing tracks,
> those are defined in local (=model) coordinates relative to each node's
> parent.
> Last but not least, there is offset (=pivot) transformation which is
applied
> before drawing the node, but is not inherited.
> So ; if you don't care about hierarchy or animation, you can simply draw
in
> world coordinates.
by Jukka Liimatt » Wed, 11 Dec 2002 06:50:07
Seems you bring the meshes into local coordinates when you are reading them,Quote:> Ok, thanks for the info. Would you have any idea then why when I draw the
> model, the meshes are in the wrong places? I have a 3ds file with 3 meshes
> and 3 materials, and when it is drawn in my program, the meshes are all on
> top of each other. I assumed it was that matrix I wasnt using. is there
> anything that defines the location of the mesh that I missed?
j.
by DeadHamste » Wed, 11 Dec 2002 07:23:07
-DH
Quote:> > Ok, thanks for the info. Would you have any idea then why when I draw
the
> > model, the meshes are in the wrong places? I have a 3ds file with 3
meshes
> > and 3 materials, and when it is drawn in my program, the meshes are all
on
> > top of each other. I assumed it was that matrix I wasnt using. is there
> > anything that defines the location of the mesh that I missed?
> Seems you bring the meshes into local coordinates when you are reading
them,
> do you use pre-written code or your own?
> j.
1. matrix math (translating and rotating)
I am having some trouble utilizing 3ds files because the meshes each have
their own origin. I have been reading in the mesh matrices, but I am not
sure how to utilize them. its a 4x3 matrix (missing the bottom row for
opengl).
first, what is the difference between these two, since they seem to have
very different effects:
glTranslatef(5,5,5);
or....
m= [1,0,0,5]
[0,1,0,5]
[0,0,1,5]
[0,0,0,1]
glMultMatrix(m);
My problem is simple. If I read in the mesh matrix from the 3ds file, and
there are no scales or rotations in it, then I can use glTranslate() to
move, and all is well. but if I use glMultMatrix() my meshes end up in the
wrong place. my mesh matrix is a float[16] and when I translate I use
values 3,7,11 from the mesh matrix to translate. I just do not understand
how to utilize this mesh matrix to get my stuff in the right location.
4. 3dmax
5. Matrix math and projections (from 3D to 2D)
7. question for matrix math experts...
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