Make sharp shadows with HDR

One advantage of the HDRi is good lighting that gives the scene and makes it more realistic, but also one of the drawbacks is making sharp shadows.

The method we used when we have a HDRi lighting the scene and we want to make sharp shadows, is to create an additional light to help make these shadows defined.

INVERSE GAMMA

In VRay to do this without adding additional light is decreasing the value of gamma. When you load the HDRi in the Material Editor, the end within the group parameters, is the Inverse gama.
A value of 0.75 to 1.0 is recommended.

COMPARE VALUES OF INVERSE GAMMA

Then you will see how decreasing the Inverse gamma can refine the quality of the shadow.

IMPORTANT FACTORS TO SHARP SHADOWS

Not all HDR produce sharp shadows, two important factors must be met:

INTENSE LIGHT SOURCE

A scenario where clearly see the center of the sun have to do sharp shadows.

PROPER CATCH HDRI

A sunny HDRi must be properly captured (EV), to cast shadows.

I hope this tutorial has been helpful.