D3D camera problems...

I decided to use Q's, because it's the easiest...

Quarternions are to rotations, what vectors are to points.

You can create a Q that represents a 5^o rotation upwards relative to the object being rotated . Sound like what you want to do?

You're going to either have to find a Q library for VB or write one yourself. It's just a little trig but I don't have the formulas in front of me.

This is my code for movement, I keep track of the elapsed time each frame (accurately) and update the postion of the object based on its velocity (linear and angular). I maintaine a Q that at any time represents the direction the object is facing (called m_qFacing). This way when they hit the up arrow, they always go forwrd in the direction they are facing, etc...

I had to play around with the axis of rotation to get yaw to be yaw, pitch to be pitch, and roll to be roll.

void CAvatar::MoveAhead(float fElapsed_sec) { float Move_m = m_fMovementRate_mps * fElapsed_sec; D3DXVECTOR3 v3Looking_At, v3Up, v3Left; D3DI3D_QuaternionToOrthoV3(v3Left, v3Up, v3Looking_At, m_qFacing); m_v3Position += Move_m * v3Looking_At; m_bMoved=TRUE; } void CAvatar::RotateRight(float fElapsed_sec) { D3DXQUATERNION dr; float Turn_r = m_fTurnRate_rps * fElapsed_sec; D3DMath_QuaternionFromAngles(dr.x, dr.y, dr.z, dr.w, 0.0f, -Turn_r, 0.0f); m_qFacing = dr * m_qFacing; m_bTurned = TRUE; }

Magmai Kai Holmlor
- Not For Rent

Edited by - Magmai Kai Holmlor on October 11, 2001 1:18:43 AM

ah, that is my problem... every web site i find about the damn quaternions either says something to the effect of "i won''t go into detail here, but they are great for rotating matrices around an arbitrary axis", or is so deep into math theory that i can''t decipher it enough to code it...
anyone have any ideas?

--- krez (krezisback@aol.com)

How bout doing what all the old games did?

Instead of rotating the camera, rotate the entire world the same degrees in the opposite direction.

This doesn''t require any more calculations than rotating the camera, since every point gets multiplied by your camera matrix.
So if you want to rotate the world instead of the camera, dump your camera matrix totally so you don''t do an extra matrix multiplication per vertex.

One problem we encountered with camera rotations using eulers was the order of application. If you do it x,y,z order you end up not having a useful pitch rotation. i.e. a free flying camera will act odd. The order we use seems to work for all cases we have used it for :-

#define ANGCOSSIN(ang, cvar, svar) \
{ \
cvar = COSF(ang); \
svar = SINF(ang); \
}

#define ANGCOSSIN3(angx, cvarx, svarx, angy, cvary, svary, angz, cvarz, svarz) \
{ \
ANGCOSSIN(angx, cvarx, svarx); \
ANGCOSSIN(angy, cvary, svary); \
ANGCOSSIN(angz, cvarz, svarz); \
}

//------------------------------------------------------------------------------
// r = rotation, radians, t = translation, s = scale
RotTransMatrix(const VECTOR *r,const VECTOR *t, const VECTOR *s, D3DMATRIX *m)
{
r32 cx,cy,cz,sx,sy,sz;

/////////////////////////////////////////////////////////
ANGCOSSIN3(r->x, cx, sx, r->y, cy, sy, r->z, cz, sz);
/////////////////////////////////////////////////////////
m->m[0][0] = (cy*cz) * s->x;
m->m[1][0] = (sx*sy - cx*cy*sz) * s->y;
m->m[2][0] = (cx*sy + cy*sx*sz) * s->z;
m->m[3][0] = 0.0f;
/////////////////////////////////////////////////////////
m->m[0][1] = (sz) * s->x;
m->m[1][1] = (cx*cz) * s->y;
m->m[2][1] = (-(cz*sx)) * s->z;
m->m[3][1] = 0.0f;
/////////////////////////////////////////////////////////
m->m[0][2] = (-(cz*sy)) * s->x;
m->m[1][2] = (cy*sx + cx*sy*sz) * s->y;
m->m[2][2] = (cx*cy - sx*sy*sz) * s->z;
m->m[3][2] = 0.0f;
/////////////////////////////////////////////////////////
m->m[3][0] = t->x;
m->m[3][1] = t->y;
m->m[3][2] = t->z;
m->m[3][3] = 1.0f;
}
This produces the world space matrix. You''ll have to transpose it to use it as a view matrix.

Note you may have to swap the row column order if its upside down.



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