[vec] Add parallax factor to toworldcoords() and toscreencoords()

vec.lua

@@ -206,66 +206,72 @@ function vec.angleto(x1,y1, x2,y2) return atan2(y1,x1) - atan2(y2,x2) end
 
 --- Transform world coordinates to screen coordinates.
 --
--- @param x (number) World coordinate X.
--- @param y (number) World coordinate Y.
--- @param vx (number|nil) Point of view X coordinate, defaults to w/2.
--- @param vy (number|nil) Point of view Y coordinate, defaults to h/2.
--- @param rot (number|nil) View rotation in radians, defaults to 0.
--- @param scale (number|nil) View scale (zoom), defaults to 1.
--- @param left (number|nil) Viewport left corner, defaults to 0.
--- @param top (number|nil) Viewport top corner, defaults to 0.
--- @param w (number|nil) Viewport width, defaults to love.graphics.getWidth().
--- @param h (number|nil) Viewport height, defaults to love.graphics.getHeight().
+-- @number x World coordinate X.
+-- @number y World coordinate Y.
+-- @number xview Point of view X coordinate, defaults to w/2.
+-- @number yview Point of view Y coordinate, defaults to h/2.
+-- @number rot View rotation in radians, defaults to 0.
+-- @number scale View scale (zoom), defaults to 1.
+-- @number left Viewport left corner, defaults to 0.
+-- @number top Viewport top corner, defaults to 0.
+-- @number w Viewport width, defaults to love.graphics.getWidth().
+-- @number h Viewport height, defaults to love.graphics.getHeight().
+-- @number xparallax Parallax factor over X, defaults to 1.
+-- @number yparallax Parallax factor over Y, defaults to 1.
 --
 -- @return (x,y) Transformed to screen coordinates according to
 --         viewport and offset.
-function vec.toscreencoords(x,y, vx,vy, rot, scale, left,top, w,h)
+function vec.toscreencoords(x,y, xview,yview, rot, scale, left,top,w,h, xparallax,yparallax)
     left,top = left or 0, top or 0
     w,h = w or love.graphics.getWidth(), h or love.graphics.getHeight()
 
     local halfw,halfh = w/2, h/2
 
-    vx,vy = vx or halfw, vy or halfh
+    xview,yview = xview or halfw, yview or halfh
     rot = rot or 0
     scale = scale or 1
+    xparallax,yparallax = xparallax or 1, yparallax or 1
 
     local sina,cosa = sin(rot),cos(rot)
 
-    x,y = x - vx, y - vy
+    x,y = x - xview*xparallax, y - yview*yparallax
     x,y = cosa*x - sina*y, sina*x + cosa*y
     return x*scale + halfw + left, y*scale + halfh + top
 end
 
 --- Transform screen coordinates to world coordinates.
 --
--- @param x (number) Screen coordinate X.
--- @param y (number) Screen coordinate Y.
--- @param vx (number|nil) Point of view X coordinate, defaults to w/2.
--- @param vy (number|nil) Point of view Y coordinate, defaults to h/2.
--- @param rot (number|nil) View rotation in radians, defaults to 0.
--- @param scale (number|nil) View scale (zoom), defaults to 1.
--- @param left (number|nil) Viewport left corner, defaults to 0.
--- @param top (number|nil) Viewport top corner, defaults to 0.
--- @param w (number|nil) Viewport width, defaults to love.graphics.getWidth().
--- @param h (number|nil) Viewport height, defaults to love.graphics.getHeight().
+-- @number x Screen coordinate X.
+-- @number y Screen coordinate Y.
+-- @number xview Point of view X coordinate, defaults to w/2.
+-- @number yview Point of view Y coordinate, defaults to h/2.
+-- @number rot View rotation in radians, defaults to 0.
+-- @number scale View scale (zoom), defaults to 1.
+-- @number left Viewport left corner, defaults to 0.
+-- @number top Viewport top corner, defaults to 0.
+-- @number w Viewport width, defaults to love.graphics.getWidth().
+-- @number h Viewport height, defaults to love.graphics.getHeight().
+-- @number xparallax Parallax factor over X, defaults to 1.
+-- @number yparallax Parallax factor over Y, defaults to 1.
 --
 -- @return (x,y) Transformed to world coordinates according to
 --         viewport and offset.
-function vec.toworldcoords(x,y, vx,vy, rot, scale, left,top,w,h)
+function vec.toworldcoords(x,y, xview,yview, rot, scale, left,top,w,h, xparallax,yparallax)
     left, top = left or 0, top or 0
     w,h = w or love.graphics.getWidth(), h or love.graphics.getHeight()
 
     local halfw,halfh = w/2, h/2
 
-    vx,vy = vx or halfw, vy or halfh
+    xview,yview = xview or halfw, yview or halfh
     rot = rot or 0
     scale = scale or 1
+    xparallax,yparallax = xparallax or 1, yparallax or 1
 
     local sina,cosa = sin(-rot),cos(-rot)
 
     x,y = (x - halfw - left) / scale, (y - halfh - top) / scale
     x,y = cosa*x - sina*y, sina*x + cosa*y
-    return x+vx, y+vy
+    return x + xview*xparallax, y + yview*yparallax
 end
 
 return vec