Rotation problem

**zak** · 18-01-2009, 13:53

hi
the enclosed program will rotate a triangle by pressing keys,
but i have trouble in the situation when i rotate the triangle some degrees to the left then stop, then rotate it down as in the attached captured small movie of a human bone. i have added some rotation in the Z direction
but it is not working as i want.
thanks for help

**Petr Schreiber** · 18-01-2009, 14:38

Hi Zak,

this is common problem I had with OpenGL too - it rotates the object, but it is not done using the object local axes, but global ones.

I attach example for you, which should do what you need, but using TBGL entity system.

Entity system calculates the transformations on its own (partially assembler optimized thanks to Charles) and then passes the final result to OpenGL.

**zak** · 18-01-2009, 15:19

Thanks Petr , As always Amazing.
i suggest to Eros to include this specific situation in the samples.
Regards

**ErosOlmi** · 19-01-2009, 12:23

Originally Posted by zak

i suggest to Eros to include this specific situation in the samples.

Done.

**Lionheart008** · 19-01-2009, 18:43

hi zak, hi all

this is common problem I had with OpenGL too - it rotates the object, but it is not done using the object local axes, but global ones.

as I have used one of the first nehe lessons with triangle (and rotation) I have had a similar problem some month ago... I can remember it very well... but I have never built a rotation with z-axes with entity system, thank you petr

good work...

If TBGL_GetWindowKeyState(hWnd, %vk_pgdn) then TBGL_EntityTurn(%sScene, %eTriangle, 0, 0, 1)

so far as I know the x-y rotation of triangle rotation did already exists

good evening, thanks for the good example, Lionheart