Tutorial about hdri lighting in Modo 801 including some set-up tips.
1. Let's start
Open new project in Modo and switch to Layout view, add Meshes > Miscellaneous > Mech Lux model to scene. Create new plane and place just under the model like seen on the picture. Later on it will be used as Shadow Catcher.
2. Loading HDRI map
Go to Shader Tree, expand Enviroments and click on Enviroment Material nested inside Environment layer. From menu above Add Layer > Image Map > (load image) and select your 32 bit hdri map. Now we have to flip environment horizontally. Go to Texture Locator and set Horizontal Wrap to -1. Also make sure that in Image Still tab Colorspace is set to Linear.
3. Render preview
When you hit F8 you should be able to see your scene nicely lit with hdri map. If there is any Directional Light you should hide it now. You can rotate hdri environment along Y axis so it fits your needs in Texture Locator > Rotation Y. If you want to change Environment Intensity click on Environment and increase or decrease value of W/srm2.
4. Environment Importance Sampling
On render preview you can notice some blotchiness visible mostly on ground plane. Since Modo 701 you can easily fix it - enable Environment Importance Sampling in Render properties. In previous versions of Modo you will have to use blurred hdri for Indirect Rays or increase Mnimum Spot value of hdri (Texture Layers > Image Map)
5. Shadow Catcher
Add material to plane and name it for instance "Shadow Catcher". Drag and move it above Base Shader. Add new Shader layer to Shadow Catcher material. Select newly created shader and in Visibility > Alpha Type change it to Shadow Catcher
6. Getting stronger shadows
Unfortunately even if you use un-clamped hdri map in Modo it is very difficult to produce sharp, visible shadows. You will have to enable Directional Light that matches sun position visible on hdri map. Add sphere mesh and apply reflective material so you can see if light is matching sun's position. To make shadows more softer increase Spread Angle value. If your model is still too dark you can add Dome Light, but keep in mind that it will increase rendering time.