Last Updated: February 25, 2016

Ruby OpenGL Walk Bounce

Pretty bouncing effect that gives an illusion that you are walking forward

Normally we would move the camera around and draw the 3D environment relative to the camera position. Here is a trick on how to do it very inexpensively.

Rotate and translate the camera position according to user commands
Rotate the world around the origin in the opposite direction of the camera rotation (giving the illusion that the camera has been rotated)

Translate the world in the opposite manner that the camera has been translated (again, giving the illusion that the camera has moved)

def update
 @ang_conv = 0.0174532925 # pi / 180
 @y_ang -= 1.5 if button? Button::KbRight
 @y_ang += 1.5 if button? Button::KbLeft

 if button?(Button::KbUp)
 @x_pos -= Math.sin(@y_ang * @ang_conv) * 0.05
 @z_diff -= Math.cos(@y_ang * @ang_conv) * 0.05
 @bounce_ang > 359 ? @bounce_ang = 0 : @bounce_ang += 10
 @bouncing = Math.sin(@bounce_ang * @ang_conv) / 20
 end

 if button?(Button::KbDown)
 @x_pos += Math.sin(@y_ang * @ang_conv) * 0.05
 @z_diff += Math.cos(@y_ang * @ang_conv) * 0.05
 @bounce_ang <= 1 ? @bounce_ang = 359 : @bounce_ang -= 10
 @bouncing = Math.sin(@bounce_ang * @ang_conv) / 20
 end

 @z_diff -= 0.3 if button? Button::KbPageUp
 @z_diff += 0.3 if button? Button::KbPageDown

 @y_pos -= 0.05 if button? Button::KbW
 @y_pos += 0.05 if button? Button::KbS
 @x_pos += 0.05 if button? Button::KbD
 @x_pos -= 0.05 if button? Button::KbA
end

def draw
 x = -@x_pos
 y = -@bouncing - 0.25
 z = -@z_diff
 scene_angle = 360 - @y_ang
 gl 
 glRotatef(@z_diff,1,0,0) #rotate to be able to look up or down
 glRotatef(scene_angle,0,1,0); #rotate on direction user is facing
 glTranslate(x, y, z) #translate the world in opposite of camera
 end
end

#ruby

#opengl

#game development