RTS/simulation overhead camera function.

[agamemnus]

It's an overhead-type camera that I made for my game.

First it sets the X, Y value, then rotates individually on all three axes, and finally it zooms in. There is no gimbal lock in this camera; it allows full 360 degree rotation on each of the three axes.

Any tips or code are welcome!

Edit 4534534: Modified the code per randomMesh's optimization.

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/* ----------------------------------------------------------------------------
 Sets the camera to the desired rotx/roty/rotz/x/y/z values.
*/

void DLL_EXPORT IrrSetCamera (irr::scene::ICameraSceneNode* camera,
                              float rotx, float roty, float rotz,
                              float x, float y , float z) {

 quaternion tempQuaternion;

 // Work out the 3 axes for the camera:
 // Forward = target (0,0,0) - position -- the position at (x=0, y=0) is (0,0,1).
 // Right = -1 * cross-product of up.
 // Pos = -forward + x * right + y * up.
 vector3df up(0,1,0);
 vector3df forward(0,0,-1);
 vector3df pos(x,y,1);

 tempQuaternion.fromAngleAxis(rotz, forward);
 tempQuaternion.getMatrix().rotateVect(up);

 tempQuaternion.fromAngleAxis(rotx, up);
 tempQuaternion.getMatrix().rotateVect(forward);

 vector3df right = forward.crossProduct (up);
 tempQuaternion.fromAngleAxis(roty, right);
 tempQuaternion.getMatrix().rotateVect(forward);
 tempQuaternion.getMatrix().rotateVect(up);

 pos = pos + z * forward;
 camera->setUpVector (up);
 camera->setTarget (pos + forward);
 camera->setPosition (pos);
}

[REDDemon]

changing the up vector is the way to go for prevent gimbal lock, why didn't you put that in code snippets? of course, is much simpler changin only the "lookAt" and the "position" parameter, but there is no reason for not updating the up vector.

you don't need to optimize that too much. it will be called only once per frame. and it seems you are doing right math so it is almost the fastest possible solution.

[randomMesh]

not sure if any more optimizations can be made.

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 vector3df up = vector3df(0,1,0);
 vector3df forward = vector3df(0,0,-1);
 vector3df right = vector3df(1,0,0);

Code: Select all

vector3df up(0,1,0);
vector3df forward(0,0,-1);
vector3df right(1,0,0);

[agamemnus]

changing the up vector is the way to go for prevent gimbal lock, why didn't you put that in code snippets? of course, is much simpler changin only the "lookAt" and the "position" parameter, but there is no reason for not updating the up vector.

I didn't feel it was very good. When I initially posted it yesterday it was a lot worse. I had a few minor brainstorms and cleaned up a lot of the code. I am honored that you think the code should be in the code snippets section.

you don't need to optimize that too much. it will be called only once per frame. and it seems you are doing right math so it is almost the fastest possible solution.

Thanks... I think maybe I can modify the fromAngleAxis code a bit more. Edit: optimized it even further by simplifying the starting position variable!
Edit 2: there still might be something not quite kosher with this function. My sea texture coordinates "jump" when my rotation angles pass something like 30 degrees... but not the other textures. IDK.

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vector3df up(0,1,0);
vector3df forward(0,0,-1);
vector3df right(1,0,0);

Thanks.

[hybrid]

not sure if any more optimizations can be made.

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 vector3df up = vector3df(0,1,0);
 vector3df forward = vector3df(0,0,-1);
 vector3df right = vector3df(1,0,0);

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vector3df up(0,1,0);
vector3df forward(0,0,-1);
vector3df right(1,0,0);

Not an optimization, but just a different syntax, though.

[randomMesh]

Not an optimization, but just a different syntax, though.

Mhh, i thought that the compiler first creates a temporary vector3df by invoking the constructor and then uses the copy constructor to initialize forward as a copy of that temporary. So wouldn't it be faster to contruct the vector3df by directly calling the constructor?

Anyway, i think it's more readable, so it's an optimization.

Btw, it's good style to do

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vector3df right(1.0f, 0.0f, 0.0f);

since the constructor of vector3df takes floats not ints and one should reflect that.

[ChaiRuiPeng]

Anyway, i think it's more readable, so it's an optimization.

C:\source\main.cpp||In function 'int main()':|
C:\\source\main.cpp|73|error: expected type qualifier before 'optimization'|

what exactly do you mean by optimization? i do not think making code easier to read would exactly mean a performance optimization.

remember

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void                     
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);;;                     ;;;;;

would be completely valid but not exactly readable

[randomMesh]

i do not think making code easier to read would exactly mean a performance optimization

It's an improvement nevertheless.

When I am working on a problem I never think about beauty. I only think about how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong.

[ChaiRuiPeng]

beauty is in the eye of the beholder though.