Perspectival shrinking of 3D text

[rain_gloom]

Could someone help with the math here?

If I have a line of length 'a' and it is 'd' distance away from the camera, how do I calculate the perspectively correct size on screen? I checked existing 3d text resources, but the only method I found is incorrect and I don't know what to google. ._.

(Part of what I'm trying to do is to replicate the "effect" system of the game "XIII", that's why I want it to be this way)

[Skuleris]

Have you tried dividing lenght by distance?

[xXMADEXx]

local fontSize = 2 -- the original text size 
local dist = getDistanceBetweenPoints3D ( x, y, z, x1, y1, z1 ); -- Set the distance with getDistanceBetweenPoints3D\ 
local allowedDistance = 13; -- The max distance you can be to see the text 
local scale = fontSize * ( ( defdd - dist ) / defdd ) 

(Formula taken from the following resource)

https://community.multitheftauto.com/index.php?p= ... ls&id=3090

[rain_gloom]

That's one I found too, I tried it. Although not as good as it should be, I think I'll settle for that. For now.