Changing character method: getDesiredSpeed

Gian-Reto · 04-10-2012 01:08 AM

I try to change the getDesiredSpeed Method of the Character class, but I have hit a brick wall here after several hours:

Code:

Flt Chr::desiredSpeed() // get desired speed

{

    // We try to calculate the height at the current position and

    // The position 1 meter ahead in move direction. From these

    // 2 Points we calculate a height difference, which we then 

    // use to increase or decrease the speed according to slope

    Vec2 oldPos = Vec2(pos().x, pos().z); 

    Flt currHeight = Game::World.hmHeight(oldPos, true);

    Vec2 offset = Vec2();

    offset.rotate(angle.x);

    offset.rotate(DegToRad(180.0f));

    offset.setLength(1.0f);

    //oldPos = Vec2(pos().x+1000.0f, pos().z+1000.0f);

    Vec2 newPos = oldPos + offset;

    //newPos = Vec2(newPos.x-1000.0f, newPos.y-1000.0f);

    Flt newHeight = Game::World.hmHeight(newPos, true);

    Flt diffHeight = (Flt) (currHeight - newHeight);

    if (diffHeight > 1.0f) diffHeight = 1.0f;

    else if (diffHeight < -1.0f) diffHeight = -1.0f;

   Flt    speed =(ctrl.flying() ? T.flying_speed : T.speed);

          speed*=Lerp(0.33f, 1.0f, anim.walk_run); // slow down when walking

          speed += diffHeight*(speed/2);

   return speed;

}

What I try to do is the following: get the current Height, calculate a new position 1 meter ahead in the walking direction, calculate height there, get the height difference, cap it to a range (1 .. -1) and use it to modify the speed.... but:

It doesn't works right no matter how I try. It always seems that even if 3 direction work fine, one is off. And I really lost track of how the Esenthel Engine tracks its positions and angles. Especially as the pos seem to not start at 0, instead the point 0 is somewhere in the middle of the map.

anyone having a better idea how to solve this problem?

Also, my second problem is performance (noticing a huge FPS drop of sometime 10 Frames)... this method seems to be called every frame, even if the character is stationary. Where is it called? Is there a possibility to change the call to not trigger so often, or to move my own code to a different method where it only triggers when the character is moving?

Salival · 04-10-2012 07:38 AM

Try something like this, not tested..

Code:

// Get current height

float oldHeight = Game::World.hmHeight(pos().xz(), 1);

// Get direction.

float range = 1.0f; // range infront of player.

Vec dir;

SinCos(dir.z, dir.x, angle.x + PI_2);

// Get position pos + dir * range

Vec dirPos = pos() + (dir * range);

// Get height from current position

float newHeight = Game::World.hmHeight(dirPos.xz(), 1);

// Calculate diff

float diff = ( newHeight - oldHeight );

// Do stuff with diff...

Gian-Reto · 04-10-2012 08:06 AM

Okay I found a solution:

Code:

Flt Chr::desiredSpeed() // get desired speed

{

    // We try to calculate the height at the current position and

    // compare it to the height at the las position.... as this

    // method gets called every fram, we need to make sure to 

    // divide the result by the amount of fps. Its a cheap 

    // approximation, but it works fine and is less computational

    // than the lookahead

    Flt fps = Time.fps();

    Vec2 currPos = Vec2(pos().x, pos().z); 

    Flt currHeight = Game::World.hmHeight(currPos, true);

    Flt diffHeight = (Flt) (currHeight - oldHeight);

    oldHeight = currHeight;

    if (diffHeight > 1/fps) diffHeight = (Flt) 1/fps;

    else if (diffHeight < -1/fps) diffHeight = (Flt) -1/fps;

   Flt    speed =(ctrl.flying() ? T.flying_speed : T.speed);

          speed*=Lerp(0.33f, 1.0f, anim.walk_run); // slow down when walking

          speed -= diffHeight*fps*(speed/2);

   return speed;

}

Its a quick and dirty hack, and the resulting slow down / speed up by terrain is not as smoth as I'd like it to be, but its easy to do and needs less computations. The Framerate is back to normal.

EDIT:
Whooops, just seen your response, Salival. I'll give it a try for sure to see how it does compared to my current solution.
Thanks for the response, its appreciated

EDIT 2:
Your solution seems to work fine, Salival. Now I can't decide which of the two possibilities to use smile

I think I'll keep yours for the moment, but leave my solution commented out as I have the faint feeling that it might be a little bit faster (though not giving such a smooth speed change, but this most probably the fault of the way the Engine calculates the height (EDIT 3: no its not, its the fault of not looking ahead, and gradually increasing the slope)) and I might need it later when my framerate drops because of other stuff going on by then.

Changing character method: getDesiredSpeed
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