Skip to main content
gamedev.net
🔒 Locked

Problem trying to set basic camera angle

Started by redas Mar 21, 2007 at 1:38 PM 11 replies 1.4k views
Original Post
redas
redas
Hi Before I have use function D3DXMatrixLookAtLH like this 

   D3DXMatrixLookAtLH
   (
      &view,
      &D3DXVECTOR3(X, Y, Z),    // the camera position
      &D3DXVECTOR3(0, 0, 0),    // the look-at position
      &D3DXVECTOR3(0.0f, 1.0f, 0.0f)  // the up direction
   );
to make my camera look at word orign. But this is bad solution if I want to move camera along x y or z axis couse it always looks at the same point. So I tryed to set cameras position and angle(Pitch,Yaw,Roll) the same way as I am doing for vertices like this 

   D3DXMatrixRotationYawPitchRoll(&rotation,D3DXToRadian(Yaw),D3DXToRadian(Pitch),D3DXToRadian(Roll));
   D3DXMatrixTranslation(&position,X,Y,Z);
   view = rotation * position;
   d3dDevice->SetTransform(D3DTS_VIEW, &view);
but something mathematicly is wrong couse camera interpretates it's position invers. I say go to position (0,0,-2) but it goes to 0,0,2. The same thing with all axes Can anyone suggest me how to make look camera to some direction depend on it's pitch,yaw,roll angles
Ouranos
Ouranos
You can still use the D3DX function to build your view matrix, just rotate the view direction vector before you pass it in rather than rotate the entire matrix.
-------------------------http://www.roachpuppy.com
redas
redas
Sorry for no replay

How do I exactly rotate vector in 3 dimension. Is there some DX function for this? I misted up a bit.
I found this formula on NET. It calculates vector (1,0) from given angle on 2D plane

NewX = Cos(Angle)*X - Sin(Angle)*YNewY = Cos(Angle)*Y + Sin(Angle)*X


Example if I want to rotate vector 45degrees i will get (0.707,0.707) it's correct but this formula is only for 2D. How can I do this for 3D (I have three angle values not one).

I gues I should use matrice here but I don't understand them very well
and I have no idea which matrice element represent vector direction(position)in final matrix like
D3DXMatrixRotationYawPitchRoll(&final_rotation_matrix,D3DXToRadian(Yaw),D3DXToRadian(Pitch),D3DXToRadian(Roll));.


is it _11,_12,_13 or _11 _21 _31...

[Edited by - redas on March 22, 2007 1:24:44 PM]
redas
redas
Can anyone at least say which picture is correct.
I am not sure 100% in which direction DX calculates angles (I use "Left-handed system")
Image Hosted by ImageShack.us

Oh God if the "A" is the right one than it looks I finaly got my camera to work :)
ibr_ozdemir
ibr_ozdemir
i'm sory but its unfortunately "Picture B"
you see when you chose "Left Hand System" (directx coor system) rotations have to be Counter ClockWise (CCW) based
redas
redas
Quote:
its unfortunately "Picture B"
Why I am not surprised :)

Damn camera still deosn't work corectly...
ibr_ozdemir
ibr_ozdemir
actually i asked a question like you ask :
Quote:
I have no idea which matrice element represent vector direction(position)in final matrix

is it _11,_12,_13 or _11 _21 _31..



its like that :

_11 : Right.x
_12 : Right.y
_13 : Right.z
_14 : 0

_21 : Up.x
_22 : Up.y
_23 : Up.z
_24 : 0

_31 : Direction.x
_32 : Direction.y
_33 : Direction.z
_34 : 0

_41 : Position.x
_42 : Position.y
_43 : Position.z
_44 : 1

anyway i didnt handle my camera object which your way, you dont have to think deeply like that
here is my solution :

your cameras are like other objects right? i mean they have own positon, rotation values if so 

procedure TCamera.PrepareCamera;begin  if CameraLocked then    ObjectAim(CameraLockedObject.AbsolutePosition,CameraUpVector);{ this part isnt so important but if like learn "Aiming" i also send that method}  FD3DDevice.SetTransform(D3DTS_VIEW,MatrixView);  FD3DDevice.SetTransform(D3DTS_PROJECTION,MatrixPerspective);end;function TCamera.MatrixView: TD3DMatrix;var  look:TD3DVector;begin  D3DXVec3Add(look,AbsolutePosition,AbsoluteDirection);  D3DXMatrixLookAtLH(Result,AbsolutePosition,look,AbsoluteUp);end;function TCamera.MatrixPerspective: TD3DMatrix;var  width,height:integer;begin    with RealScreenRect do {this is for multi camera games or some thing else you dont have to add that code you can just use screen width and height}    begin      width:=Right-Left;      height:=Bottom-Top;    end;    if Perspective then {this is for perspective and ortho cameras}      D3DXMatrixPerspectiveFovLH(Result,PointOfView,width/height,ZNear,ZFar)    else      D3DXMatrixOrthoLH(Result,width/(PointOfView*100),height/(PointOfView*100),        ZNear,ZFar);end;
ibr_ozdemir
ibr_ozdemir
if you want to learn values of variables (like PointOfView, ZNear, ZFar) or something else i can explain
redas
redas
ibr_ozdemir thank you for trying to help.

Yes my camera is like other objects, it has X,Y,Z and Pitch,Yaw,Roll properties.
So let's say now I want to set my camera. What will I do? afcourse I will use
D3DXMatrixLookAtLH() couse all tutorials shows it;
   D3DXMatrixLookAtLH   (      &view,      &D3DXVECTOR3(X, Y, Z),    // the camera position <= wow it's cool I can just simply pass object's position properties      &lookat,    // the look-at position <= this is my nightmare      &D3DXVECTOR3(0.0f, 1.0f, 0.0f)  // the up direction   );


All parameters of this function are good just how they are except "look-at".
Ye it's good if you want have static camera or you want make camera to fallow
for example a ball, afcourse camera will not change it's position but it will change it's angles.

Exactly "look-at"parameter and is my PROBLEM. What I wish to do is get some kind of direction vector calculated from given angles (Pitch,Yaw,Row).
Let's say I wish to make camera be rotated 45 degrees around Y axis,
then my direction(look-at) vector should become (0.707, 0, 0.707) let's take another example "Rotate camera 30 degrees around Y axis" than look-at vector should be (0.866, 0, 0.5).

Current camera render function code looks like that
   D3DXMatrixRotationX(&mat_pitch,D3DXToRadian(Pitch));   D3DXMatrixRotationY(&mat_yaw,D3DXToRadian(Yaw));   D3DXMatrixRotationZ(&mat_roll,D3DXToRadian(Roll));   mat_rotation = mat_yaw * mat_pitch * mat_roll;   lookat.x = mat_rotation._31;   lookat.y = mat_rotation._32;   lookat.z = mat_rotation._33;   D3DXVec3Add(&lookat,&D3DXVECTOR3(X, Y, Z),&lookat);   D3DXMatrixLookAtLH   (      &mat_view,      &D3DXVECTOR3(X, Y, Z),    // the camera position      &lookat,    // the look-at position      &D3DXVECTOR3(0.0f, 1.0f, 0.0f)  // the up direction   );   d3dDevice->SetTransform(D3DTS_VIEW, &mat_view);// set the view transform   D3DXMatrixPerspectiveFovLH   (      &mat_projection,      D3DXToRadian(60),    // the horizontal field of view      Aspect,    // aspect ratio      1.0f,    // the near view-plane      Range   );   d3dDevice->SetTransform(D3DTS_PROJECTION, &mat_projection); // set the projection transform


this code version is allmost good becouse:
1. It doesn't interpretate camera position inversly
2. It looks like it rotates to correct direction along X and Y axis, BUT it has no effect on Z axis.
What am I doing wrong?

What is the right order to multiply transformation matrices. Is this one correct?
"scale * rotationY * rotationX * rotationZ * position"


Now here's how I understand PointOfView, ZNear, ZFar:
PointOfView - This is point(vector) where camera looks for example 0,0,0 it will looks at word orign
ZNear - it's the distance from camera position at which camera actulay starts to see something. I set it to 1.0f
ZFar - it's distance from camera position where camera stops to see. I set it to big number 1024.0f. So ZFar - ZNear = camera view range

[Edited by - redas on March 23, 2007 9:08:24 AM]
ibr_ozdemir
ibr_ozdemir
first i have to say that "PointOfView" is very incapable word, its not some kind of Point-Of-View, sory

its "flovy", actually you can see flovy in D3DXMatrixPerspectiveFovLH method...anyway

i make my camera matrix like this:
(there is no scale factor for cameras but i'm goingto add that code to)

function Object.Matrix:TD3DMatrix;var  m:TD3DMatrix;begin  //following code make matrix for every child objects, i mean "local matrix"  D3DXMatrixTranslation(Result,Axis.x,Axis.y,Axis.z);{this is for axis you dont have to do that but its good for rotating something like legs, arms etc. you got the idea}  D3DXMatrixIdentity(m);  with m do  begin    _11:=Right.x*Scale.x;      _12:=Right.y*Scale.x;      _13:=Right.z*Scale.x;    _21:=Up.x*Scale.y;         _22:=Up.y*Scale.y;         _23:=Up.z*Scale.y;    _31:=Direction.x*Scale.z;  _32:=Direction.y*Scale.z;  _33:=Direction.z*Scale.z;  end;  D3DXMatrixMultiply(Result,Result,m);  D3DXMatrixTranslation(m,Positon.x,Positon.y,Positon.z);  D3DXMatrixMultiply(Result,Result,m);  //following code make "world matrix" for object  if Parent<>nil then    D3DXMatrixMultiply(Reslut,Result,Parent.Matrix);end;


if you want learn how am i filling Right, Up, Direction vector i can show them
redas
redas
What represents this vector?
Direction

- is it eular angles in radians/degrees
- or it's a point where camera should look?
- or its something like unit vector (0.707, 0, 0.707)
ibr_ozdemir
ibr_ozdemir
maybe this help you

following code transform eular angles (rotation) to directions
procedure RotationToDirection(Rotation:TD3DVector; var Direction, Up, Right:TD3DVector);var  m,m2:TD3DMatrix;begin  D3DXMatrixRotationX(m2,-DegToRad(Rotation.X));  D3DXMatrixRotationY(m,-DegToRad(Rotation.Y));  D3DXMatrixMultiply(m2,m2,m);  D3DXMatrixRotationZ(m,-DegToRad(Rotation.Z));  D3DXMatrixMultiply(m2,m2,m);  Right:=D3DXVector3(m2._11,m2._12,m2._13);  Up:=D3DXVector3(m2._21,m2._22,m2._23);  Direction:=D3DXVector3(m2._31,m2._32,m2._33);end;

and its up to you but its better if you make your camera look side "direction"
TheAdmiral
TheAdmiral
Quote:
Original post by redas
   D3DXMatrixRotationYawPitchRoll(&rotation,D3DXToRadian(Yaw),D3DXToRadian(Pitch),D3DXToRadian(Roll));   D3DXMatrixTranslation(&position,X,Y,Z);   view = rotation * position;   d3dDevice->SetTransform(D3DTS_VIEW, &view);

Watch out. Direct3D uses row-vectors, so the transformation of M on x is Mx, not xM. For this reason, transformation matrices compose in the order of:
M<sub>composition</sub> = M<sub>last</sub>...M<sub>second</sub>M<sub>first</sub>.
Perhaps you'd have some more success if the view matrix was calculated using
view = position * rotation
Also, D3DXMatrixTranslation creates a matrix that translates by (x, y, z). If you'd like (x, y, z) to end up at the origin, you should write
D3DXMatrixTranslation(&position, -X, -Y, -Z)

Admiral
Ring3 Circus - Diary of a programmer, journal of a hacker.

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.

Sign in to reply to this topic.