i am pretty new to c++ and dark gdk. im trying to make a simple platform game to start off. i have the basic controls down, the animations, and collision. but i am having much trouble finding how to create the effects of gravity. please help.

What exactly do you mean?

If you have an object moving, and you want gravity to account for its movement, then
you can just do this :

const float GRAVITY = -9.8;
ball.x += ball.velocity.x * dt;
ball.y += ball.velocity.y + GRAVITY * dt;

Those follow from basic Newtonian equation.

Shouldn't this be:
ball.y += ball.velocity.y + GRAVITY * dt;
ball.y += ball.velocity.y*dt + (GRAVITY*dt*dt)/2

Gravity should be treated as a (physics)vector. In a 2-D scenario the Gravity vector will have 2 components. X & Y.

struct LineVector
  float x;
  float y;

LineVector Gravity;
Gravity.x = +0.0f;  //Since gravity acts only in vertical direction
Gravity.y = -9.8f;

Going by Newton's equations in a non-inertial frame:
S = ut + (at^2)/2 , S :displacement, u :initial velocity, t :time
They will split into X-Y with each component contributing in displacement. And the net displacement will be:
sqrt( Sx^2 + Sy^2 ) Where Sx : is X component of Displacement & similarly for Sy.
& deviation will be tangent^-1(Sy/Sx)
Speaking in simpler terms:

ball.x += ball.velocity.x*dt + (GRAVITY.x*dt*dt)/2
ball.y += ball.velocity.y*dt + (GRAVITY.y*dt*dt)/2
/* You can either move the ball using Cartesian coordinates or polar. */

Thanks for the replies but this wont work. I'm looking for something that would create more of a parabola for the ball to follow.

Parabolic trajectory is nothing but a velocity vector under the influence of non-perpendicular deceleration(gravity).

Edited 6 Years Ago by nbaztec: n/a

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