SetScissorClip

From OxeyeWiki

video.setScissorClip(x, y, width, height)
Sets the video device's "scissor clip" area. This area is a rectangle on the screen in which rendering should be allowed. All pixels that are rendered outside of this rectangle will not be displayed. The scissor clip can be used, for example, to create split-screen multiplayer. To do this, render the whole game twice, using an on-screen off-set for the second half. See the example below. Use clearScissorClip to reset the clip again.
Parameter	Expected Type	Description
x	An integer	The left edge of the rectangle.
y	An integer	The top edge of the rectangle.
width	An integer	The width of the rectangle.
height	An integer	The height of the rectangle.
Returns
Returns nothing.

Example

local function renderSplit(offsetX, offsetY)
   -- render all sprites etc
end

local function renderAll()

   local screenW, screenH = video.getScreenSize()

   -- split vertically (one view on the left and one on the right)
   local halfWidth = screenW / 2

   -- render player A's view
   video.setScissorClip(0, 0, halfWidth, screenH)
   renderSplit(0, 0)

   -- render player B's view
   video.setScissorClip(halfWidth, 0, screenW, screenH)
   renderSplit(halfWidth, 0)

   -- reset clip
   video.clearScissorClip()

   -- render shared stuff here, such as top layer GUI etc
end