Flip Sprite - Make a sprite appear to rotate in 3-D space.

 

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This behavior makes a sprite appear to rotate in 3-D space around the Y-axis of the screen. The perspective illusion can be adjusted, as well as the speed of "flippage." Makes a fun visual effect.

-- Behavior by Ken Loge - kenl@ori.org -- Special thanks to Aaron Cram for the algorithm -- Version 1.0 -- 05-05-01 property pAngle property pOriginalQuad -- original quad of the sprite property pSpriteQuad -- the quad of the sprite at any given moment of change property pSpriteWidth property pSpriteHeight property pXl -- use for quad offset property pXr property pYl property pYr property pFlipSpeed -- speed of rotation 1=slow, 100=fast negative=opposite direction property pPerspective -- perspective illusion, 0=orthographic, 20=normal on beginSprite me   -- initialize values for float math   pAngle = 0.0   pXl = 0.0   pXr = 0.0   pYl = 0.0   pYr = 0.0   -- get initial sprite values   pOriginalQuad = sprite(me.spriteNum).quad   pSpriteWidth = sprite(me.spriteNum).width   pSpriteHeight = sprite(me.spriteNum).height end on getBehaviorDescription me   return "Flips a sprite continuously around the Y axis with a 3-D perspective illusion." end on getPropertyDescriptionList me   list = [:]   addProp list, #pFlipSpeed, [#comment: "Flip Speed:", #format: #integer, #default: 10, #range: [#min: -100, #max: 100]]   addProp list, #pPerspective, [#comment: "Perspective Factor:", #format: #integer, #default: 20, #range: [#min: 0, #max: 50]]   return list end on exitFrame me   -- changing the cos() functions below to sin() and   -- the sin() functions to cos() reverses the direction of rotation   pSpriteQuad = sprite(me.spriteNum).quad   -- there's probably a much more elegant way to do the following, but it works   pXr = pSpriteWidth / 2   pXl = pSpriteWidth / 2   pXr = pXr * cos(pAngle)   pXl = pXl * cos(pAngle + 3.14)   pSpriteQuad[1].locH = pXl + sprite(me.spriteNum).loc[1]   pSpriteQuad[2].locH = pXr + sprite(me.spriteNum).loc[1]   pSpriteQuad[3].locH = pXr + sprite(me.spriteNum).loc[1]   pSpriteQuad[4].locH = pXl + sprite(me.spriteNum).loc[1]   pYr = sin(pAngle) * pPerspective   pYl = sin(pAngle + 3.14) * pPerspective   pSpriteQuad[2].locV = pOriginalQuad[2].locV - pYr   pSpriteQuad[3].locV = pOriginalQuad[3].locV + pYr   pSpriteQuad[1].locV = pOriginalQuad[1].locV - pYl   pSpriteQuad[4].locV = pOriginalQuad[4].locV + pYl   sprite(me.spriteNum).quad = pSpriteQuad   if pAngle > 6.28 then pAngle = 0   if pAngle < 0 then pAngle = 6.28   pAngle = pAngle - pFlipSpeed / 100.0 end