Camera Rotation

What, no replies???
Surely someone can help me???

Polar Coords? I had the same problem and theese worked for me in GL though. Theres a tutorial somwhere on here.

[edited by - pkelly83 on August 16, 2003 12:11:11 PM]

Camera questions never get decent replies. Don''t know if it''s because they''re always being asked. Most say cameras are really simple but no one can ever explain them properly.

However, after a lot of research there are a few camera classes out there that you may learn from. I, myself, do not fully understand them but maybe you will.

The one at gametutorials in the opengl section is ok, once you convert it to d3d. The one at ttp://www.ultimategameprogramming.com/DirectX1.htm is very similar to the one at gametutorials. I also had a german one somewhere but can''t find it, it was posted as a news item a couple months back.

Yeah we should get somone to write a decent tutorial. Cause I asked a camera question before and got a crap answer too. Sorry if my own answer was crap! But no seriously we should have a decent one somwhere. There''s one on www.gametutorials.com but I don''t understand it very well, when I tried to copy it my program didn''t work quiet right.

I already have the one from GameTutorials and it explains how to do rotation about the Y-Axis. What i want is rotation going up and down.

I am thinking that if i rotated about the strafe vector of the object i am looking at it should work, but what function rotates about an arbitrary angle. Oh yeah, there is D3DXMatrixRotationAxis but how would i use it? Would i pass the strafe vector in???

ANY CODE?????????? OR PSUEDOCODE???????

X- rotation

quote:

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Original post by dagamer34
I am thinking that if i rotated about the strafe vector of the object i am looking at it should work, but what function rotates about an arbitrary angle. Oh yeah, there is D3DXMatrixRotationAxis but how would i use it? Would i pass the strafe vector in???

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That''s one way. Rotate around the Y axis, then rotate around the rotated strafe vector. The other way is to first rotate around the world X axis (which should be the strafe vector without rotation), then rotate around the world Y axis. Both do the same thing except the order is reversed.

Umm... any code???? Besides, you would need to know how much to rotate and you can only do that if you know the angle of the vector from the view to the position. Any body know how to get the angle from a vector on a plane like the x-z( the one i will be using)???

And please post code too if you have it.

There is no fun to begin with if you have a deadline

I gave it a shot. It didn''t work. Here is the code i came up with.

/* m_vView and m_vPosition are D3DXVECTOR3''s by the way */

/* Move to the origin so we can rotate along the axises
without problems */
D3DXMATRIX translate;
D3DXVECTOR3 vtranslate = m_vView - m_vPosition;
D3DXMatrixTranslation (&translate, vtranslate.x, vtranslate.y,
vtranslate.z);

/* Find the angle between (0, 0, 0) and our current position */
float angle = atan2 (m_vPosition.x, m_vPosition.z);

/* Rotate along the y-axis */
D3DXMATRIX matrixY;
D3DXMatrixRotationY (&matrixY, angle);

/* Rotate along the z-axis */
D3DXMATRIX matrixZ;
D3DXMatrixRotationX (&matrixZ, D3DXToRadian (fSpeed));

/* Move back */
D3DXMATRIX translate2 = -translate;
D3DXVECTOR3 vtranslate2 = -vtranslate;
D3DXMatrixTranslation (&translate2, vtranslate2.x, vtranslate2.y,
vtranslate2.z);

/* Now we build the matrix */
D3DXMatrixLookAtLH (&m_matView, &m_vPosition, &m_vView,
&m_vUpVector);

//m_matView = m_matView * translate * matrixY * matrixZ * translate2;

}

I am working on a 3rd person game myself... Here''s some sample
code of what i do to determine the camera angle:

m_pPlayer is the player object

m_pPlayer.vLoc is a vector which contains the player''s current (x,y,z) location

m_fDistanceFromPlayer is the distance between the camera and player

m_vCameraLoc is a D3DXVECTOR3 containing the camera position

// Min and max camera distance from the player
FLOAT fMinDistance = 10.0f;
FLOAT fMaxDistance = 100.0f;

// Zoom camera in
if( m_UserInput.bCameraZoomIn && m_fDistanceFromPlayer > fMinDistance )
m_fDistanceFromPlayer -= 1.0f;

// Zoom camera out
if( m_UserInput.bCameraZoomOut && m_fDistanceFromPlayer < fMaxDistance )
m_fDistanceFromPlayer += 1.0f;

// Calculate the camera angle (180 degrees or opposide of whatever the player''s y-axis rotation is)
const FLOAT fAngle = m_pPlayer.fAngle + DEGTORAD(TWOPI);

// Calculate the camera''s x-axis position
m_vCameraLoc.x = m_pPlayer.vLoc.x + m_fDistanceFromPlayer * sinf( fAngle );

// Calculate the camera''s z-axis position
m_vCameraLoc.z = m_pPlayer.vLoc.z + m_fDistanceFromPlayer * cosf( fAngle );

// The y-axis is always the same for my game
m_vCameraLoc.y = 5.0f;

// Set the eye point
D3DXVECTOR3 vEyePt = D3DXVECTOR3( m_vCameraLoc.x, m_vCameraLoc.y, m_vCameraLoc.z );

// Set the look at point (i have it looking at the player)
D3DXVECTOR3 vLookatPt = D3DXVECTOR3( m_pPlayer.vLoc.x, m_pPlayer.vLoc.y, m_pPlayer.vLoc.z );

// Up vector (i''m still new and still dont know what this is)
D3DXVECTOR3 vUpVec = D3DXVECTOR3( 0.0f, 1.0f, 0.0f );

// Set the new view matrix
D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
m_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );

Mike Cunningham (First year student)

Umm.. you didn''t answer my question.

i want to rotate the camera UP and DOWN. kinda like super mario sunshine without the zooming in at the same time.

I know there are 2 ways to do it:

#1: The mathematically easy way

Get the strafe vector(cross of view and up) and rotate around it. Some reason it didn''t work

#2 The HARD WAY (this should work too but doesn''t)

Move the camera to the origin PLUS the look at point coordinates. So if the camera was at (10, 10, 10) and it was looking at (5, 5, 5) i would then move it to (5, 5, 5).

Then i would rotate the camera until it is aligned with the x axis by rotating it about the y-axis. Then rotate about the z-axis and the rotate it back to the angle it was. Then i move it back and voila it works.

Or at least it should have.

SOME HELP HERE!!!!!!

Wouldn''t you just have to increment or decrement the y-axis coordinate of the lookat vector if you wanted to Look up, or down?

Mike Cunningham (First year student)

Try this. (There might be a better way to do it, but it works for me.)

Assuming you have the camera's position, look-at, and up vectors:
- Get the "front" vector which is the vector between the position and look-at point.
- Get the length (d) of the front vector.
- Get the strafe vector using the cross product of the up and front vectors.
- Use D3DXMatrixRotationAxis(&m, ✗, angle) where m will be the rotation matrix.
- Do D3DXVector3Transform(&newup, &up, &m)
- Do D3DXVector3Transform(&newfront, &front, &m)
- Update the up and front vectors using newup and newfront.
- EDIT: Forgot to normalize the new front vector.
- Update the lookat point by doing: lookat = position + (d*front);

Hopefully, I got that right.

-HQ

[edited by - HQ-SOFT on August 16, 2003 11:59:11 PM]

how do iget it so that the character always is "behind" the camera???