How could I make this bounding box coordinates code faster?

Help and Feedback Code Review
#1

This code is part of a function that is called thousands of times in the render stepped function of my code. Thing is, this takes up 1/3 of the time in the function and yet it isnt iterating through anything! This is a huge bottle neck and I want to see how I can make this faster. It’s goal is to return the min and max coordinates of a bounding box of a triangle

    local a=Vector2.new(math.floor(aP.X), math.floor(aP.Y))
    local b=Vector2.new(math.floor(bP.X), math.floor(bP.Y))
    local c=Vector2.new(math.floor(cP.X), math.floor(cP.Y))
    local maxX = a.x
    local maxY = a.y
    local minX = a.x
    local minY = a.y

    --max coordinate
    if maxX < b.x then
        maxX = b.x
    end
    if maxX < c.x then
        maxX = c.x
    end

    if maxY < b.y then
        maxY = b.y
    end
    if maxY < c.y then
        maxY = c.y
    end

    --min coordinate
    if minX >= b.x then
        minX = b.x
    end
    if minX >= c.x then
        minX = c.x
    end

    if minY >= b.y then
        minY = b.y
    end
    if minY >= c.y then
        minY = c.y
    end
#3

The if-statements can be simplified using math.min and math.max.

local a = Vector2.new(math.floor(aP.X), math.floor(aP.Y))
local b = Vector2.new(math.floor(bP.X), math.floor(bP.Y))
local c = Vector2.new(math.floor(cP.X), math.floor(cP.Y))

local minX = math.min(a.X, b.X, c.X)
local maxX = math.max(a.X, b.X, c.X)
local minY = math.min(a.Y, b.Y, c.Y)
local maxY = math.max(a.Y, b.Y, c.Y)

I am not sure if optimizing this code will actually solve your performance issues. Maybe somehow calling the function less per RenderStep is the most effective solution.

#4

That code doesnt work in my program

EDIT: yep, went from 1/3 to 1/15th

1 Like
#5

I forgot to include the a vector.

#7

I’m not sure if its faster, but I use this: http://www.sunshine2k.de/coding/java/TriangleRasterization/TriangleRasterization.html (Use the standard algorithm).

1 Like
#8

Do ap.X, ap.Y, ... remain constant? If so, you can cache the vectors created instead of creating them every frame.

#9

I have to use that due to internal reasons. I need them to rounded down for consistensy stakes and I need them to be actual for my barycentric coordinate algorithm (and they do change when i apply my perspective matrices/translations)