How to find strafe vectors?

[kornerr]

In main loop I update camera position to match object position. I use FPS camera, so I have mouse movements cooked for me. But that doesn't suit for keys, and I have to manually move object with keys.
Well, I can move object forward and backward very easy, because I can just get camera position and target. But how will I get left or right strafe vectors?
Thanks.

[kornerr]

it turned out that if (x, y) is my forward vector, then (-y, x) is the left vector

[Mikenoworth]

That one Irr modder who make a library and has a funny stickfigure avatar has some good code for what you want. Here, I use it myself:

Code: Select all

	
irr::core::vector3df WorldUpVector = irr::core::vector3df( 0.0f, 1.0f, 0.0f );

	irr::core::vector3df cameraPosition = GetCamera()->getPosition();
	irr::core::vector3df cameraTarget = GetCamera()->getTarget();

	// Compute new forward vector 
	irr::core::vector3df forwardVector = cameraTarget - cameraPosition; 
	// Set the Y to 0 so the vectors are calculated on the XZ plane 
	forwardVector.Y = 0.0f; 
	forwardVector.normalize(); 

	// Compute new right vector 
	irr::core::vector3df rightVector = WorldUpVector.crossProduct ( forwardVector ); 
	rightVector.normalize(); 

	// Compute new up vector 
	irr::core::vector3df upVector = forwardVector.crossProduct( rightVector ); 
	upVector.normalize(); 

You can't just copy-n-paste-n-compile, but the basic ideas are there. Having these vectors makes it so much easier to implement your own camera movement. Gah I wish I could remember his nick, Spintz?

[kornerr]

Thanks, Mikenoworth.
But all this works only when camera was created as FPS one. When I create basic one, instead of moving left/right it turns around center :/
How to make it move, not turn?
Thanks.

[sudi]

Ok lets say ur character is standing still at the beginning with a rotion of 0° degrees around the y(up)-axis. then u cpul dfor exampel say that:

0 0 1 is forward
0 0 -1 is backward
1 0 0 is strafe right
-1 0 0 is strafe left

this works as long you don't rotate your character but i guess u want to turn him as well therefor u use a matrix. simply do:

irr::core::matrix4 mat;
mat.setRotationDegrees(the rotation of the character around the Y-Axis)

mat.transform(forward);
mat.transform(backward);
mat.transform(strafe right);
mat.transform(strafe left);

and tada it works

[Spintz]

That one Irr modder who make a library and has a funny stickfigure avatar has some good code for what you want

LOL, you like my stick figure!!!!

[zehsound.dude]

Hello ppl

I realize this thread is a year old but I just started using Irrlicht and since this was confusing me and couldn't find it anywhere in the forums, I thought I should post it in case someone else is confused by it too. I also JUST figured out how to do this the way I wanted it to work.

But all this works only when camera was created as FPS one. When I create basic one, instead of moving left/right it turns around center :/
How to make it move, not turn?

all you do is move the camera target by the vectors that you move the camera position by.

so therefore...

Code: Select all

irr::core::vector3df WorldUpVector = irr::core::vector3df( 0.0f, 1.0f, 0.0f );

   irr::core::vector3df cameraPosition = GetCamera()->getPosition();
   irr::core::vector3df cameraTarget = GetCamera()->getTarget();

   // Compute new forward vector
   irr::core::vector3df forwardVector = cameraTarget - cameraPosition;
   // Set the Y to 0 so the vectors are calculated on the XZ plane
   forwardVector.Y = 0.0f;
   forwardVector.normalize();

   // Compute new right vector
   irr::core::vector3df rightVector = WorldUpVector.crossProduct ( forwardVector );
   rightVector.normalize();

   // Compute new up vector
   irr::core::vector3df upVector = forwardVector.crossProduct( rightVector );
   upVector.normalize(); 

  // Then to "slide" the camera to the right and change camera target to move with it
  GetCamera->setPosition( GetCamera->getPosition() + rightVector);
  GetCamera->setTarget(GetCamera->getTarget() + rightVector);

if you want to rotate the camera... you still gotta figure that out

ps: this is my first post evah!

[rogerborg]

You popped your post cherry by sharing knowledge? I think I love you. Let's hug. Good touch hug.