Mukund

01-03-2012, 06:53 AM

Hello,

I am trying to get billboarding to work. I needed a little clarification. This is the way i tried:

From the modelview, i obtain the following:

-- --

| x1 y1 z1 -|

| x2 y2 z2 -|

| x3 y3 z3 -|

| - - - -|

-- --

[(x1, x2, x3) is the vector that provides the X orientation]

[ ** '-' implies i'm not using that part of the matrix]

Using the x vector, find the angle between that and

[0, 0, -1] So, this would be the angle i need to rotate the billboard on the y axis.

Let this angle be "Ang"

So, what i'm trying is:

1) Rotate scene by "rot" angle on the Y axis.

2) Using the modelview, obtain "Ang" Now, rot will be equal to Ang. So, i just do a negative rotation of Ang on the Y axis.

ie.

. Rotate scene by rot

. Obtain Ang

. Rotate object by -Ang

This seems to work. I am trying for billboarding on only one axis. Is there a better way? Or is this method fine?

Thanks!

I am trying to get billboarding to work. I needed a little clarification. This is the way i tried:

From the modelview, i obtain the following:

-- --

| x1 y1 z1 -|

| x2 y2 z2 -|

| x3 y3 z3 -|

| - - - -|

-- --

[(x1, x2, x3) is the vector that provides the X orientation]

[ ** '-' implies i'm not using that part of the matrix]

Using the x vector, find the angle between that and

[0, 0, -1] So, this would be the angle i need to rotate the billboard on the y axis.

Let this angle be "Ang"

So, what i'm trying is:

1) Rotate scene by "rot" angle on the Y axis.

2) Using the modelview, obtain "Ang" Now, rot will be equal to Ang. So, i just do a negative rotation of Ang on the Y axis.

ie.

. Rotate scene by rot

. Obtain Ang

. Rotate object by -Ang

This seems to work. I am trying for billboarding on only one axis. Is there a better way? Or is this method fine?

Thanks!