ModLab is described as 'Free tool to generate and process Normal, Roughness and Curvature map'. There are more than 10 alternatives to ModLab for Windows, Linux and Mac. The best alternative is AwesomeBump, which is both free and Open Source. Other great apps like ModLab are Quixel Suite (Freemium), Materialize - by Bounding Box Software (Free, Open Source), Laigter (Free, Open Source) and xNormal (Free).
AwesomeBump is an open source program designed to generate normal, height, specular or ambient occlusion textures from a single image. Since the image processing is done in 99% on GPU the program runs very fast and all the parameters can be changed in real time.
Quixel was founded in 2011 by Teddy Bergsman and Waqar Azim, based on the vision of substantially speeding up how creators build digital environments, by giving them access to a vast and ever-expanding library of 3D building blocks, and easy-to-use tools to greatly simplify the...
Materialize is a stand alone tool for creating materials for use in games from images. You can create an entire material from a single image or import the textures you have and generate the textures you need.
xNormal is an application to generate normal / ambient occlusion / displacement maps. It can also project the texture of the highpoly model into the lowpoly mesh ( complete texture transfer, even with different topologies ).
NVIDIA Melody creates high quality normal maps that make a low-poly model look like a high-poly model. Simply load your low-poly working model, then load your high-poly reference model, click the "Generate Normal Map" button and watch Melody go to town.
Knald is the world’s first GPU powered solution for generating “bake quality” textures from any 2D source texture. Knald generates textures commonly used to create games, like Normal, Derivative, Displacement/Height, Ambient Occlusion, Concavity and Convexity maps.