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# Camera rotation

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Lets say I have a camera struct given by

typedef struct cam_type{
vec3_t pos;
vec3_t orig_pos;
} cam_t;

typedef struct vec3_type{
float x, y, z;
} vec3_t;

The position of the cam is relative to the world''s origin. If I was to rotate this camera around the world''s y-axis, would its distance from the origin always be the same? Also, isn''t the length of this vector then its distance from the origin? I am doing the rotation by the following code and this doesn''t seem to be happening. Its position is (2.0,3.0,4.0).

cam_t *cam = Cam_Init(2.0,3.0,4.0); /* pos and orig_pos setup */
mat4x4_t *rot;
float a;
float rot_step = PI / 36.0;

for(a = 0.0; a <= (PI * 2); a += rot_step){
rot = Mat4x4_YRotation(a);
Vec3_Transform(&(cam->pos), rot); /* transforms the vec3_t by rot */
printf("length = %f\n", Vec3_Length(&(cam->pos));
Vec3_Copy(&(cam->orig_pos), &(cam->pos)); /* copy original position back */
}

Every 2PI it is back to its original position and length but in between it isn''t working. Thanks.

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world.OM; //worldspace rotation matrix
world.TM; //worldSpace Translation ma.
world.EM //eye matrix

camera.OM; //camera rotation Matrix
camera.TM; //camera translation matrix

world.EM.unit();
world.TM.unit();
world.OM.unit();

world.OM.setRot(x,y,z); //rotate
world.TM.setTans(x0,y0,z0); //than translate

world.EM.mul(OM); //rotate
world.EM.mul(TM); //than translate

//now the camera stuff
camera.OM.unit();
camrea.TM.unit();

camrea.OM.setRot(cxDir, cyDir, czDir);
camera.TM.setTrans(-cx, -cy, -cz);

//everything depends on the order of multiplication
world.EM.mul(camera.OM);
world.EM.mul(camera.TM);

transform(nvert, world.EM);

this should give u a feeling for what has to happen while calculation all the matr. stuff.

learn to use u''re finger and u''re position in a room as the orignin of the 3d-space. when doing a rotation just rotate about the depending axis represented by u''re finger and look to than direction, when translating, walk throug the room.

have phun:

-thanks to bush for destroying my childrens futur; stop that madness-

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Thanks.

One thing I don''t understand is what do these do

world.EM.unit();
world.TM.unit();
world.OM.unit();

camera.OM.unit();
camrea.TM.unit();

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unit() i assume normalizes the vector to unit length 1 (one).
However these are matricies...
Maybe it clears the matricies to all 1''s or an identity matrix? Just ideas, lol

||--------------------------||
Black Hole Productions
http://bhp.e-chrono.net/
Resident expert on stuff
max621@barrysworld.com
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Yeah, I was thinking it would change them to the identity matrix but I wanted to check.

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stoip wasting oure time by asking stupendous questions, go on read tut. if u wanna really know. this all is basic stuff.
go on and read, there are hundrets of good tut. on 3d-math.
when not understanding something come back and ask...

bybylamer

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quote:
Original post by bloemschneif
stoip wasting oure time by asking stupendous questions, go on read tut.

the only one wasting your time is yourself.
he has every right to ask any question he likes, and
you have every right to ignore it.
time and find something productive to do.

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