Converting 3D Geometry Into
Displacement Maps
By Neil Blevins
Created On: Jan 25th 2022
There are many techniques and tools for converting 3d Geometry into
displacement maps, especially for transferring details from a highres
mesh to a lowres mesh in games. This lesson is about a quick and dirty
method I've used to convert 3d greebles into displacement maps.
Starship Hulls
Many of you have seen the Starship Hull images I've made,
example below...
A lot of people were surprised when I showed that these images
weren't 3d geometry or displacement, they mostly used a photoshop trick
for shadowing and beveling edges. Read more about it here: Painting
Starship Panels In Photoshop
But late last year I decided, just for fun, to make a few similar
images that were actual displacement maps. Here's the result...
Here's the displacement map I made...
And the result of the displacement using the map above on a plane...
For the main paneling, I painted displacement values inside of
photoshop. But for some of the smaller greebles, like these...
I made 3d geometry, and then converted that geometry into
displacement maps, and then added them to my hand painted displacement.
So this lesson will be about how I did that 3d to disp map
conversion.
Process
So first I modeled some greebles in 3dsmax (although a similar workflow
can be done in pretty much any piece of software), here's an example...
Our goal is to displace this plane into the same shape as the 3d
geometry.
So I want to convert the 3d geometry in a displacement map. In a
displacement map, the value white means something is high, and a value
of black means something is low, with grey values somewhere in between.
So, I take the highres geometry and assign a flat color material with a
gradient in the diffuse slot. This could be a Standard material with
100% self illumination, but since I'm using vray, I'm using a
VrayLightMtl with the gradient ramp in the color slot.
For the Gradient Ramp map, the only thing I adjusted was the rotation
to -90, so my gradient went up and down instead of right to left.
Now I select my 3d geometry and add a Planar uvwMap from the side like
this...
Now I assign the flat color material to my 3d geometry, and then render
from the Top Viewport, and I get a result like this...
That's my displacement map for my plane, again, white are the highest
areas, black the lowest, and the color comes from that gradient
projected from the side.
So I hide my 3d geometry, unhide my plane, and assign a turbosmooth to
the plane, setting it to add a bunch of extra faces...
Then I add a displace Modifier, and place my rendered displacement map
on the map slot...
I then render my plane, which looks sorta right, but it's too flat for
some reason.
This is because our Strength (or in other words, height) is set wrong
for the displace modifier. It's using the default of 1.0. What should
be the correct strength? I could eyeball it, but let's find out more
directly. If I select my original 3d geometry, go to the Utilities tab,
and go to the Measure tool, I see that my original geometry is 8.613
units in the Z dimension...
So my original object is 8.613 units high. Which means the value of
black in my displacement map represents a height of 0, and a value of
white represents 8.613 units high. So to get an identical height with
my displacement, I need to change my Displacement strength from the
default of 1.0 to 8.613. Now lets check the render...
One nice thing about the Displace Modifier is you can see the result in
the viewport. Here's me double checking that the height of the
displacement matches the height of the geometry in the front viewport.
The purple is my 3d Geometry, the white is my displaced plane. Looks
pretty much identical...
But if you don't care about seeing the result in the viewport, and
you're a vray user, you could also use the vray displacement modifier
instead of the turbosmooth and displace modifier. Here's the settings I
used to get identical results...
Adjust the edge length down to get a cleaner but slower to render
result.
Conclusion
If you need to make a really complex displacement map with overhangs or
of a really complex surface, there are other better techniques out
there. But if your needs are simple, like adding pebbles on a flat
terrain or some vents to an enormous scifi megastructure, this
technique may be the way to go. So give it a try!
