-- This demo renders a scene with several uses of stencil maps (skip down to comment "Stencils here")
--
-- Sample contributed by andi mcc
local scene = {}
function scene.load()
-- So we can see the effects of the stencils, we want to put some things in our scene.
-- A checkerboard floor:
scene.floorSize = 6
-- A series of sideways-drifting cubes (these will be stenciled)
scene.driftCubeCount = 60
scene.boundMin = vector(-10, -1, -10)
scene.boundMax = vector( 10, 9, 10)
scene.speed = 1
scene.driftCubeSize = 0.6
scene.driftCubes = {}
for i = 1, scene.driftCubeCount do
scene.generateDriftCube(i, true)
end
-- A 3x3 cube made of two different stencil types
scene.stencilCubeCenter = vector(0, 1.5, -0.5)
scene.stencilCubeSize = 0.25
scene.stencilCubeRotate = 0
scene.stencilCubeRotateSpeed = 1
scene.stencilCubes = {}
for z = -1, 1 do
for y = -1, 1 do
for x = -1, 1 do -- Iterate over every cube
if not (x==0 and y==0 and z==0) then -- Except the center
table.insert(scene.stencilCubes, { vector(x,y,z), math.random(1,2) }) -- Cube center and stencil type
end
end
end
end
-- Three cubemap skyboxes, of different colors
scene.skybox = {}
local skyboxTextureSize = 32
local bandSize=3
for cube_index,colors in ipairs{
{{ 1, 0.5, 1 }, { 1, 1, 1 }}, -- Fuschia and white
{{ 1, 1, 0.5 }, { 0, 0, 0 }}, -- Yellow and black
{{ 1, 1, 1 }, { 0.9, 0.9, 0.9 }}, -- White and silver
} do
local layers = {}
for layer = 1, 6 do -- 6 layers to a cubemap
local data = lovr.data.newImage(skyboxTextureSize, skyboxTextureSize, 'rgba8')
for y = 1, skyboxTextureSize do
for x = 1, skyboxTextureSize do
local isBorder = x == 1 or x == skyboxTextureSize or y == 1 or y == skyboxTextureSize -- Solid color in corners
local direction = cube_index==3 and -1 or 1 -- Reverse direction on third cubemap
local whichColor = (isBorder or ((x + direction * y - 2) % (bandSize * 2) >= bandSize)) and 1 or 2 -- Diagonal stripes
data:setPixel(x - 1, y - 1, unpack(colors[whichColor]))
end
end
table.insert(layers, data)
end
table.insert(scene.skybox, lovr.graphics.newTexture(layers))
end
scene.sampler = lovr.graphics.newSampler({ filter = 'nearest' })
end
local function randomQuaternion()
local u, v, w = math.random(), math.random(), math.random()
return quaternion.pack(
math.sqrt(1 - u) * math.sin(2 * v * math.pi),
math.sqrt(1 - u) * math.cos(2 * v * math.pi),
math.sqrt(u) * math.sin(2 * w * math.pi),
math.sqrt(u) * math.cos(2 * w * math.pi)
)
end
function scene.generateDriftCube(i, randomX) -- Generate one cube with random position and color and a random rotational velocity
local cube = {}
local x, y, z
if randomX then
x = scene.boundMin.x + math.random() * (scene.boundMax.x - scene.boundMin.x)
else
x = scene.boundMin.x
end
y = scene.boundMin.y + math.random()*(scene.boundMax.y-scene.boundMin.y)
z = scene.boundMin.z + math.random()*(scene.boundMax.z-scene.boundMin.z)
cube.at = vector(x, y, z)
cube.rotateBasis = randomQuaternion()
cube.rotateTarget = cube.rotateBasis:conjugate()
cube.rotate = cube.rotateBasis
scene.driftCubes[i] = cube
end
function scene.update(dt) -- On each frame, move each cube and spin it a little
for i, cube in ipairs(scene.driftCubes) do
cube.at = cube.at + vector(scene.speed * dt, 0, 0)
if cube.at.x > scene.boundMax.x then -- If cube left the scene bounds respawn it
scene.generateDriftCube(i)
else
local rotateAmount = (cube.at.x - scene.boundMin.x) / (scene.boundMax.x - scene.boundMin.x)
cube.rotate = cube.rotateBasis:slerp(cube.rotateTarget, rotateAmount)
end
end
-- Also rotate the center cube
scene.stencilCubeRotate = scene.stencilCubeRotate + dt * scene.stencilCubeRotateSpeed
end
function scene.draw(pass)
-- Drawing without culling can make stencils or transparency look weird. We'll be using both...
pass:setFaceCull('back')
-- First, draw the skybox
pass:setSampler(scene.sampler)
pass:skybox(scene.skybox[3])
-- Next, draw a floor
local floorRecenter = scene.floorSize / 2 + 0.5
for x = 1, scene.floorSize do
for y = 1, scene.floorSize do
if (x + y) % 2 == 0 then
pass:setColor(0.25, 0.25, 0.25)
else
pass:setColor(0.35, 0.35, 0.35)
end
pass:plane(x - floorRecenter, 0, y - floorRecenter, 1, 1, -math.pi / 2, 1, 0, 0) -- Face up
end
end
pass:setColor(1, 1, 1, 1)
-- Stencils here
-- Using stencils involves drawing twice, once with a stencil write set and once with a stencil test set.
-- Example 1: Using stencils to "paint" scenes
-- Each sub-cube in our 3x3 cube will write a different value to the stencil buffer, 1 or 2.
pass:setColorWrite() -- In the color spectrum, these cubes are completely invisible! They write only stencil and depth.
pass:push() -- Position ourselves in the right place
pass:translate(scene.stencilCubeCenter)
pass:rotate(scene.stencilCubeRotate, 0,1,0)
for _, cube in ipairs(scene.stencilCubes) do
local center, stencilValue = unpack(cube)
-- Draw to stencil (but only when we pass the depth test)
pass:setStencilWrite({'keep', 'keep', 'replace'}, stencilValue)
pass:cube(center * scene.stencilCubeSize, scene.stencilCubeSize)
end
pass:pop()
pass:setStencilWrite() -- Reset stencil write
pass:setColorWrite(true) -- Reset color write
-- Now that we've painted the stencil buffer, let's draw something with depth, like a skybox
pass:setDepthTest() -- Turn off depth test because the skybox is "behind" the cubes
for stencilValue = 1, 2 do
pass:setStencilTest('equal', stencilValue) -- Commands after here will only draw on pixels where the stencil value is right
pass:skybox(scene.skybox[stencilValue])
end
pass:setDepthTest('gequal') -- Turn depth test back on
-- Example 2: Using stencils to prevent collision
-- Here we will write AND test the stencil at the same time! In this step we want to draw a bunch of 50%-transparent cubes,
-- But we don't want any cubes to overlap each other. We want each cube to look like a "world of shadow".
-- The cubes can darken the skybox and the 3x3 cube, but not any pixel where another cube has already drawn.
pass:setStencilTest('notequal', 3) -- We will write the value "3", but refuse to write any pixel where a 3 is already present.
pass:setStencilWrite('replace', 3) -- Note we haven't cleared the stencil buffer, so we can't reuse values 1 or 2.
for _, cube in ipairs(scene.driftCubes) do
pass:setColor(0.75, 0.5, 0.5, 0.5)
pass:cube(cube.at, scene.driftCubeSize, cube.rotate)
end
-- The stencil state will reset at the end of this lovr.draw, but let's clear it anyway.
pass:setStencilWrite()
pass:setStencilTest()
end
-- Handle lovr
function lovr.load()
lovr.graphics.setBackgroundColor(1, 0, 0) -- Red to show up clearly if something goes wrong
scene.load()
end
function lovr.update(dt)
scene.update(dt)
end
function lovr.draw(pass)
scene.draw(pass)
end