Hello guys,
I have a problem with the ASE Format. I need informations, about *NODE_TM, i can’t imagine what this should say to me. I hope someone can explain me this.
Thank you for reply
helda
It contains the transformation information.
I need more details because i don’t know how to use this information on my Vertex coordinates, on my faces and normals.
it contains information about how the object is to be transformed. The data is stored twice : once as a matrix, and once in affine decomposition. But be careful : due to a nasty bug in the ASE exporter, only the matrix is guaranteed to be valid. So you have only to read TM_ROWx, where x=0,1,2,3.
it gives you the modelview (mv) matrix to pass to glMultMatrixd.
here’s how it’s stored :
TM_ROW0 mv[0] mv[1] mv[2]
TM_ROW1 mv[4] mv[5] mv[6]
TM_ROW2 mv[8] mv[9] mv[10]
TM_ROW3 mv[12] mv[13] mv[4]
note that the 4 remaining coeffs are not written because they are always the same :
mv[3]=mv[7]=mv[11]=0
mv[15]=1
[This message has been edited by Morglum (edited 01-10-2003).]
I didn’t know about that bug.
Am I correct in saying that ASE files already have the transformations applied to the vertices? - the file actually contains the world coords rather than the local coords. I seem to remember this was the case for an ascii format exported from MAX.
yes that’s right. (at least for the standard ase exporter that comes with 3dsmax).
The bug appears when an object has been applied a ‘mirror symmetry’ (or whatsoever it’s being called in 3dsmax).
This transformation is of determinant -1, which, in affine decomposition, can only be obtained by using negative scale factors (since rotations have always det=1). But 3dsmax still exports positive scale factors, which is wrong. That results in objects that are displayed upside down.
EDIT
this last statement is false of course.
The correct statement is :
That results in objects that are displayed with normal vectors upside down.
[This message has been edited by Morglum (edited 01-10-2003).]
that means, when i want to draw my triangles i must do the following:
glPushMatrix()
load the exportet matrix;
draw the Szene
glPopMatrix()
helda
exactly.
careful, as said above, the vertices are already transformed. So you have to transform them back before doing that : or else the transfo will be applied twice. For that you invert the matrix, and you multiply the vecs by the inverted matrix.
a simpler option (valid only if you don’t have anims) is to apply the matrix directly to the normals. Then you’re done.
Thank you i think this will help me!
helda
hehe I remember I was exactly in your situation 1 year ago. These hints were given to me by Eric…
by the way i’m developing a variant of the ASE format (which I call AME like ascii model export) which is especially fit for single models (no cameras, no lights).
It would be bug free and would have animations stored in matrix form (hence easy to read, as opposed to ASE’s inextricable pos+rot+scale).
If anyone is interested, I can already give the 3dsmax .AME exporter.
I’m now working on a .AME loader that would convert .AME into a real, usable format (which would include strippified, state-sorted geometry).
Yes i’m very intrested, because it won’t do as it should!
helda
first i want to do the easier solution, i want to apply the matrix to the normal.
i make it like this
glPushMatrix();
glMultMatrixf(transformation);
glNormal3f(…,…,…)
glPopMatrix()
i do this for every normal, but it had no effect.
helda
Processing only occurs with a call to glVertex (or a similar command that begins vertex processing). Modifying and then restoring the matrix without first calling glVertex will have no effect.
How will it then be possible?
helda
Just compute directly, without ogl calls,
matrix * normal.
Here is the rule to multiply a matrix by a vector :
newvector [i] = mat [i] * oldvector [0] + mat [i+4] * oldvector [1] + mat [i+8] * oldvector [2] + mat [i+12] * oldvector [3];
PS i’ll upload the .AME exporter ASAP. But I first have to write the documentation, or it’s useless.
[This message has been edited by Morglum (edited 01-10-2003).]
sorry, i hope this is my last question.
How must i handle the ROW3? in the moment i have a 4x4 Matrix and a vector with 3 elements(normal). And what is exactly in this row of the matrix?
helda
good question !
you’ve got a 4x4-matrix m4 and a 3-vector v3, so that doesn’t fit.
Answer :
float v4 [4];
v4[0] = v3[0];
v4[1] = v3[1];
v4[2] = v3[2];
v4[3] = 1.0; //add new 4th component equal to 1.0
v4 = m4 * v4; //do the multiplication
v3[0] = v4[0] / v4[3]; //retrieve the multiplied v3
v3[1] = v4[1] / v4[3];
v3[2] = v4[2] / v4[3];
hope that helps
PS this time you can have the AME plugin + doc. I’ve posted a thread on this forum.
This ‘row’ of the matrix (in fact it should have been named a column) represents the position, ie, it’s a vector by which you translate your object.
The translation is implicitly being done in the matrix multiplication.
I think this is OK! but when i do this, my sphere looks like a disc. And the Illumination of the sphere is in all driangles the same.
I have done it before with the 3x3 Matrix (row 0,1,2) and this looks better. But there when i have test it with a cube, there are only 2 sides in light.
helda