Draw some heart

[turgenevivan]

Thanks for the cool lua lib.

play with keyboard 1/2/3.

Lua Code

local fenster = require('fenster')

local width = 500
local height = 500
local fps = 30

local window = fenster.open(width, height, 'Hello fenster!', 1, fps)

-- Heart shape function
local function heart(x, y)
    -- https://mathworld.wolfram.com/HeartCurve.html
    -- Convert window coordinates to mathematical coordinates, using window center as origin
    local xp = (x - width / 2) / (width / 3)  -- Scale factor for x
    local yp = (height / 2 - y) / (height / 3)  -- Scale and invert y because y increases downwards

    -- Heart equation: (x^2 + y^2 - 1)^3 = x^2 * y^3
    return (xp^2 + yp^2 - 1)^3 - xp^2 * yp^3 <= 0
end

-- Define the heart shape function with a pattern using level sets
local function heart_with_pattern(x, y)
    -- https://en.wikipedia.org/wiki/Level_set
    -- Convert window coordinates to mathematical coordinates, using window center as origin
    local xp = (x - width / 2) / (width / 3)  -- Scale factor for x
    local yp = (height / 2 - y) / (height / 3)  -- Scale and invert y

    -- Heart level set function
    local z = xp * xp + yp * yp - 1
    local f = z * z * z - xp * xp * yp * yp * yp

    -- Mapping result to color intensity (like characters in the original code)
    if f <= 0.0 then
        -- Map 'f' value to grayscale intensity based on the same idea as character mapping
        local intensity = math.floor((f * -8.0) % 8)  -- Same concept as indexing into characters
        local shades = {
            0x000000, -- Black (represents '@')
            0x222222, -- Dark gray (represents '%')
            0x444444, -- Medium dark gray (represents '#')
            0x666666, -- Gray (represents '*')
            0x888888, -- Light gray (represents '+')
            0xaaaaaa, -- Lighter gray (represents '=')
            0xcccccc, -- Very light gray (represents ':')
            0xffffff  -- White (represents '.')
        }
        local shades = {
            0x330000, -- Dark red (represents '@')
            0x660000, -- Darker red (represents '%')
            0x990000, -- Medium dark red (represents '#')
            0xcc0000, -- Medium red (represents '*')
            0xff0000, -- Bright red (represents '+')
            0xff3333, -- Light red (represents '=')
            0xff6666, -- Lighter red (represents ':')
            0xffffff  -- White (represents '.')
        }
        return shades[intensity + 1]  -- Return color based on intensity
    else
        return 0xffffff  -- Background white
    end
end

-- Define the heart shape function f(x, y, z)
local function f(x, y, z)
    local a = x * x + (9.0 / 4.0) * y * y + z * z - 1
    return a * a * a - x * x * z * z * z - (9.0 / 80.0) * y * y * z * z * z
end

-- Define h(x, z) function to find the surface at a given x and z
local function h(x, z)
    for y = 1.0, 0.0, -0.001 do
        if f(x, y, z) <= 0.0 then
            return y
        end
    end
    return 0.0
end


local function draw_heart_with_pattern()
    for x = 0, width - 1 do
        for y = 0, height - 1 do
            local color = heart_with_pattern(x, y)
            window:set(x, y, color)  -- Set pixel color based on the level set function using hex
        end
    end
end

local function draw_heart()
    for x = 0, width - 1 do
        for y = 0, height - 1 do
            if heart(x, y) then
                window:set(x, y, 0xff0000) -- Set red color for the heart shape
            end
        end
    end
end

local function draw_heart3d()
    for sy = 0, height - 1 do -- same
        local z = 1.5 - sy * 3.0 / height  -- Map screen coordinates to z
        for sx = 0, width - 1 do
            local x = sx * 3.0 / width - 1.5  -- Map screen coordinates to x
            local v = f(x, 0.0, z)  -- Evaluate the heart equation
            local r = 0  -- Red channel value

            if v <= 0.0 then
                local y0 = h(x, z)  -- Get the y value at (x, z)
                local ny = 0.0011  -- Small offset for normal calculation
                local nx = h(x + ny, z) - y0  -- Calculate the normal x component
                local nz = h(x, z + ny) - y0  -- Calculate the normal z component
                local nd = 1.0 / math.sqrt(nx * nx + ny * ny + nz * nz)  -- Normalize
                local d = (nx + ny - nz) * nd * 0.5 + 0.5  -- Calculate brightness
                r = math.floor(d * 255.0)  -- Map to 0-255 range
            end
            
            -- Ensure red channel is clamped between 0 and 255
            r = math.max(0, math.min(255, r))
            
            -- Set the pixel color (R, G, B)
            window:set(sx, sy, (r * 2^16) + (0 * 2^8) + 0)  -- Only red color
        end
    end
end

-- Draw the heart shape with color
local function draw_heart3d_animate(t)
    -- Heart scaling based on time (to create the pulsing effect)
    local s = math.sin(t)
    local a = s * s * s * s * 0.2  -- Scaling factor based on sine wave

    for sy = 0, height - 1 do
        local z = 1.5 - sy * 3.0 / height  -- Map screen coordinates to z
        z = z * (1.2 - a) -- animate
        for sx = 0, width - 1 do
            local x = sx * 3.0 / width - 1.5  -- Map screen coordinates to x
            x = x * (1.2 + a) -- animate
            local v = f(x, 0.0, z)  -- Evaluate the heart equation
            local r = 0  -- Red channel value

            if v <= 0.0 then
                local y0 = h(x, z)  -- Get the y value at (x, z)
                local ny = 0.0011  -- Small offset for normal calculation
                local nx = h(x + ny, z) - y0  -- Calculate the normal x component
                local nz = h(x, z + ny) - y0  -- Calculate the normal z component
                local nd = 1.0 / math.sqrt(nx * nx + ny * ny + nz * nz)  -- Normalize
                local d = (nx + ny - nz) * nd * 0.5 + 0.5  -- Calculate brightness
                r = math.floor(d * 255.0)  -- Map to 0-255 range
            end
            
            -- Ensure red channel is clamped between 0 and 255
            r = math.max(0, math.min(255, r))
            
            -- Set the pixel color (R, G, B)
            local color = fenster.rgb(r, 0, 0)
            window:set(sx, sy, color)  -- Only red color
        end
    end
end


local draw_menu = {
    [1] = draw_heart,
    [2] = draw_heart_with_pattern,
    [3] = draw_heart3d,
    [4] = draw_heart3d_animate,
}
local draw_type = 1

local t = 0
while window:loop() and not window.keys[27] do
    window:clear()

    if window.keys[string.byte('1')] then
        draw_type = 1
    elseif window.keys[string.byte('2')] then
        draw_type = 2
    elseif window.keys[string.byte('3')] then
        draw_type = 3
    elseif window.keys[string.byte('4')] then
        t = 0
        draw_type = 4
    end

    draw_menu[draw_type](t)
    t = t + 0.1  -- Update time
end

windows playground.
playground.zip

https://github.com/rrcenter/lua-fenster-playground

[jonasgeiler]

This is really awesome! Great work!
Do you mind if I add this to the demos folder?

[turgenevivan]

Thanks for like it.

Please feel free to modify and add it to demo.

[turgenevivan]

key 4:

---

local width = 144
local height = 144
local window_scale = 4

---

-- Draw the heart shape with color
local function draw_heart3d_animate(t)
    -- Heart scaling based on time (to create the pulsing effect)
    local s = math.sin(t)
    local a = s * s * s * s * 0.2  -- Scaling factor based on sine wave

    for sy = 0, height - 1 do
        local z = 1.5 - sy * 3.0 / height  -- Map screen coordinates to z
        z = z * (1.2 - a) -- animate
        for sx = 0, width - 1 do
            local x = sx * 3.0 / width - 1.5  -- Map screen coordinates to x
            x = x * (1.2 + a) -- animate
            local v = f(x, 0.0, z)  -- Evaluate the heart equation
            local r = 0  -- Red channel value

            if v <= 0.0 then
                local y0 = h(x, z)  -- Get the y value at (x, z)
                local ny = 0.0011  -- Small offset for normal calculation
                local nx = h(x + ny, z) - y0  -- Calculate the normal x component
                local nz = h(x, z + ny) - y0  -- Calculate the normal z component
                local nd = 1.0 / math.sqrt(nx * nx + ny * ny + nz * nz)  -- Normalize
                local d = (nx + ny - nz) * nd * 0.5 + 0.5  -- Calculate brightness
                r = math.floor(d * 255.0)  -- Map to 0-255 range
            end
            
            -- Ensure red channel is clamped between 0 and 255
            r = math.max(0, math.min(255, r))
            
            -- Set the pixel color (R, G, B)
            local color = fenster.rgb(r, 0, 0)
            window:set(sx, sy, color)  -- Only red color
        end
    end
end