Terrain:GetSlope

This method gets the terrain slope at the specified coordinate or 3D position.

Syntax

• float GetSlope(const int tx, const int ty)
• float GetSlope(const iVec2& coord)
• float GetSlope(const Vec3& coord)
• float GetSlope(const float x, const float y, const float z)

Returns

Returns the terrain slope in degrees at the specified coordinate or the interpolated normal at the specified position in global space.

Example

This example applies a material to a terrain based on the slope at each point.

-- Get the display list
local displays = GetDisplays()

-- Create a window
local window = CreateWindow("Ultra Engine", 0, 0, 1280, 720, displays[1], WINDOW_CENTER + WINDOW_TITLEBAR)

-- Create a world
local world = CreateWorld()
world:SetAmbientLight(0)

-- Create a framebuffer
local framebuffer = CreateFramebuffer(window)

-- Create a camera
local camera = CreateCamera(world)
camera:SetFov(70)
camera:SetPosition(0, 50, 0)
camera:SetRotation(45, 0, 0)
camera:SetClearColor(Vec4(0.125))

-- Sunlight
local light = CreateDirectionalLight(world)
light:SetRotation(45, 35, 0)
light:SetColor(2)

-- Create terrain
local terrain = CreateTerrain(world, 512)
terrain:LoadHeightmap("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Terrain/512.r16")
terrain:SetScale(1, 100, 1)

-- Create base material
local ground = CreateMaterial()
local diffusemap = LoadTexture("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Materials/Ground/river_small_rocks_diff_4k.dds")
local normalmap = LoadTexture("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Materials/Ground/river_small_rocks_nor_gl_4k.dds")
ground:SetTexture(diffusemap, TEXTURE_BASE)
ground:SetTexture(normalmap, TEXTURE_NORMAL)
local groundlayer = terrain:AddLayer(ground)
terrain:Fill(groundlayer)

-- Create paint material
local rocks = CreateMaterial()
diffusemap = LoadTexture("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Materials/Ground/Rocks_Dirt_Ground_2k.dds")
normalmap = LoadTexture("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Materials/Ground/Rocks_Dirt_Ground_2k_dot3.dds")
local dispmap = LoadTexture("https://raw.githubusercontent.com/UltraEngine/Documentation/master/Assets/Materials/Ground/Rocks_Dirt_Ground_2k_disp.dds")
rocks:SetTexture(diffusemap, TEXTURE_BASE)
rocks:SetTexture(normalmap, TEXTURE_NORMAL)
rocks:SetTexture(dispmap, TEXTURE_DISPLACEMENT)

local rocklayer = terrain:AddLayer(rocks)

-- Apply material based on terrain slope
for x = 0, terrain.resolution.x - 1 do
    for y = 0, terrain.resolution.y - 1 do
        local slope = terrain:GetSlope(x, y)
        if slope > 15.0 then
            local wt = Min((slope - 15.0) / 10.0, 1.0)
            terrain:SetLayerWeight(rocklayer, x, y, wt)
        end
    end
end

-- Camera controls
camera:AddComponent(CameraControls)

-- Main loop
while not window:Closed() and not window:KeyDown(KEY_ESCAPE) do
    world:Update()
    world:Render(framebuffer)
end