LitDev's "Small Basic: Dynamic Graphics" - Featured Article!

Article
12/25/2013

Check out LitDev's November gold medal winner for the Small Basic Guru contest:

This is also LitDev's first gold medal! So congrats go to LitDev!

Here is an excerpt section from the article...

===============

Advanced Collisions

To get sprites to bounce off each other realistically can be complicated. Basically we need to do the collision in a center of mass reference frame using geometry like the figure below, then convert from the center of mass frame back to the actual frame.

This is an example implementation of this in Small Basic.

Sub ``CollisionCheck

``For ``i ``= ``1 ``To ``Ball_Number``-``1

``For ``j ``= ``i``+``1 ``To ``Ball_Number

``dx ``= ``Ball_X``[``i``] ``- ``Ball_X``[``j``]

``dy ``= ``Ball_Y``[``i``] ``- ``Ball_Y``[``j``]

``Distance ``= ``Math``.``SquareRoot``(``dx ``* ``dx ``+ ``dy ``* ``dy``)

``If ``Distance ``< ``Ball_Diameter ``Then

``Cx ``= ``(``Ball_vX``[``i``]``+``ball_vX``[``j``]``)``/``2

``Cy ``= ``(``Ball_vY``[``i``]``+``ball_vY``[``j``]``)``/``2

``Relative_vX``[``i``] ``= ``Ball_vX``[``i``] ``- ``Cx

``Relative_vY``[``i``] ``= ``Ball_vY``[``i``] ``- ``Cy

``Relative_vX``[``j``] ``= ``Ball_vX``[``j``] ``- ``Cx

``Relative_vY``[``j``] ``= ``Ball_vY``[``j``] ``- ``Cy

``Nx ``= ``dx ``/ ``Distance

``Ny ``= ``dy ``/ ``Distance

``L``[``i``] ``= ``Nx ``* ``Relative_vX``[``i``] ``+ ``Ny ``* ``Relative_vY``[``i``]

``L``[``j``] ``= ``Nx ``* ``Relative_vX``[``j``] ``+ ``Ny ``* ``Relative_vY``[``j``]

``Relative_vX``[``i``] ``= ``Relative_vX``[``i``] ``- ``(``2 ``* ``L``[``i``] ``* ``Nx``)

``Relative_vY``[``i``] ``= ``Relative_vY``[``i``] ``- ``(``2 ``* ``L``[``i``] ``* ``Ny``)

``Relative_vX``[``j``] ``= ``Relative_vX``[``j``] ``- ``(``2 ``* ``L``[``j``] ``* ``Nx``)

``Relative_vY``[``j``] ``= ``Relative_vY``[``j``] ``- ``(``2 ``* ``L``[``j``] ``* ``Ny``)

``Ball_vX``[``i``] ``= ``(``Relative_vX``[``i``] ``+ ``Cx``)

``Ball_vY``[``i``] ``= ``(``Relative_vY``[``i``] ``+ ``Cy``)

``Ball_vX``[``j``] ``= ``(``Relative_vX``[``j``] ``+ ``Cx``)

``Ball_vY``[``j``] ``= ``(``Relative_vY``[``j``] ``+ ``Cy``)

``Ball_X``[``i``] ``= ``Ball_X``[``i``] ``+ ``Nx ``* ``(``Ball_Diameter``-``Distance``)

``Ball_Y``[``i``] ``= ``Ball_Y``[``i``] ``+ ``Ny ``* ``(``Ball_Diameter``-``Distance``)

``Ball_X``[``j``] ``= ``Ball_X``[``j``] ``- ``Nx ``* ``(``Ball_Diameter``-``Distance``)

``Ball_Y``[``j``] ``= ``Ball_Y``[``j``] ``- ``Ny ``* ``(``Ball_Diameter``-``Distance``)

``EndIf

``EndFor

EndSub

If this is not clear then perhaps avoid this or consider trying using a physics engine to do it for you, such as the LDPhysics (Box2D) method.

===============

Here are all the winning Small Basic articles from November:

Small Basic Technical Guru - November 2013

Gold Award Winner

litdev

Dynamic Graphics

Ed Price: "Incredibly detailed. A fantastic resource to keep coming back to! From the comments: "Wanted to say WOW - this is great!" and "Awesome. Thanks""

Silver Award Winner