Castlevania Collision box viewer (FCEUX)

local px = 0x38C
local py = 0x354
local pl = 0x45

local ex = 0x38C
local ey = 0x354

local function hex(val)
    val = string.format("%X",val)
    return val
end

local function whip()
    local box = {0,0,0} -- xoff/yoff/xrad/yrad
    local wtype = memory.readbyte(0x70)
    local pos = bit.band(memory.readbyte(0x434),0x7F)  -- Simons acting positon (jumping/crouching, etc...)
    box[1] = rom.readbytesigned(0x1E46D + wtype)
    wtype = wtype * 2
    box[2] = rom.readbytesigned(0x1E470 + pos)
    box[3] = rom.readbyte(0x1E474 + wtype)
    box[4] = rom.readbyte(0x1E475 + wtype)

    if memory.readbyte(0x450) == 1 then  -- Simon is facing left
        box[1] = box[1] * -1
        box[3] = box[3] * -1
    end
    return box
end

local function player()
    local x = memory.readbyte(px)
    local y = memory.readbyte(py)
    local box
    gui.box(x+4,y+memory.readbyte(0x5F),x-4,y-memory.readbyte(0x5F),"#0000FF40","#0000FFFF")

    if memory.readbyte(0x568) == 0x11 then -- Whip is active
        box = whip()
        gui.box(x+box[1]+box[3],y+box[2]+box[4],x+box[1]-box[3],y+box[2]-box[4],"#FFFFFF40","#FFFFFFFF")
    end

end

local function buildbox(i)
    local box = {0,0}  -- xrad/yrad
    local offset = memory.readbyte(0x434 + i)
    local dracform
    if offset == 0x1D then
        dracform = memory.readbyte(0x7A)
        if dracform == 1 then  -- Dracula's 2nd form
            offset = 0x30 * 2
        else  -- Dracula's 2nd form
            offset = offset * 2
        end
    else
        offset = offset * 2
    end

    box = { rom.readbyte(0x1E47A + offset),rom.readbyte(0x1E47B + offset) }

    return box
end

local function getcolor(x)
    local color = {0,0} -- Fill/Outline
    if x >= 0x28 and x < 0x30 then
        color = {"#FFA50040","#FFA500F0"}
    elseif x >= 0x30 and x <= 0x35 then
        return color
    elseif x == 0x17 then -- Simon subweapon
        color = {"#00FFFF40","#00FFFFFF"}
    elseif x == 0x1D then -- Dracula invuln box
        color = {"#FF000040","#FFFFFFFF"}
    else
        color = {"#FF000040","#FF0000FF"}
    end
    return color
end

local function objects()
    local x
    local y
    local active
    local box
    local etype
    local c
    local oob

    for i = 4,20,1 do
        oob = memory.readbyte(0x300 + i)
        if oob == 0 or oob == 0x80 then
            box = buildbox(i)
            etype = memory.readbyte(0x434 + i)
            c = getcolor(etype)
            x = memory.readbyte(ex + i)
            y = memory.readbyte(ey + i)
            gui.box(x+box[1],y+box[2],x-box[1],y-box[2],c[1],c[2])
            if etype == 0x1D then -- Dracula's invuln box
                gui.line(x+box[1],y,x-box[1],y)
                gui.line(x,y+box[2],x,y-box[2])
            end
        end
    end
end


emu.registerafter(function()
    player()
    objects()
end)