Sprite:setStencilOperation

Revision as of 00:36, 3 February 2021 by MoKaLux (talk | contribs) (mostly formatting :-) and removed language)

Available since: Gideros 2017.6
Class: Sprite

Description

Allows to set a stencil operation to be used when drawing this sprite.

Sprite:setStencilOperation(op)


The op table can contain the following fields:

  • stencilClear: (boolean) whether the stencil should be cleared beforehand
  • stencilMask: (integer) the mask value used in stencil operations
  • stencilWriteMask: (integer) the mask value used when writing to stencil
  • stencilRef: (integer) the reference value used in stencil operations
  • stencilFunc: (integer) the stencil function to use
  • stencilFail: (integer) the stencil operation when stencil test failed
  • depthFail: (integer) the stencil operation when depth test failed
  • depthPass: (integer) the stencil operation when depth test has passed

Stencil function and operations code are defined in Sprite.STENCIL_xxx fields and correspond to the GL_xxx relevant values in OpenGL stencil documentation https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glStencilFunc.xhtml.

Parameters

op: (table) a table containing the stencil operation settings, or nil to disable stencil

Example

A glowing ticket effect:

-- STENCILOPERATION @hgy29
local bg = Bitmap.new(Texture.new("gfx/vip/background.png"))
local ticket = Bitmap.new(Texture.new("gfx/vip/ticket.png"))
local text = Bitmap.new(Texture.new("gfx/vip/text.png"))
local fx1 = Bitmap.new(Texture.new("gfx/vip/fx1.png"))
local fx2 = Bitmap.new(Texture.new("gfx/vip/fx2.png"))
 
stage:addChild(bg) bg:setScale(0.5)
stage:addChild(ticket) ticket:setPosition(80,20) ticket:setScale(0.5)
ticket:addChild(fx1) fx1:setX(-100)
fx1:addChild(fx2) fx2:setX(-100)
ticket:addChild(text)
 
-- Use auto layout on ticket to center text automatically
ticket:setLayoutParameters{ rowWeights = {1}, columnWeights = {1} }
text:setLayoutConstraints{}

-- Use stencil for masking glow:
-- 1) Clear stencil and set it to '1' for every pixel drawn on 'ticket'
ticket:setStencilOperation{
	stencilClear = true, stenciMask = 1, stencilWriteMask = 1, stencilRef = 1,
	stencilFunc = Sprite.STENCIL_ALWAYS, depthPass = Sprite.STENCIL_REPLACE
}
--2) Only draw fx1/fx2 if stencil isn't 0
fx1:setStencilOperation{
	stencilClear = false, stencilMask = 1, stencilRef = 0,
	stencilFunc = Sprite.STENCIL_NOTEQUAL
}
 
local dir = 1
stage:addEventListener(Event.ENTER_FRAME, function()
	if fx1:getX() > 450 then
		dir = -1
	elseif fx1:getX() < -100 then
		dir = 1
	end
	fx1:setX(fx1:getX() + dir*5)
end)