Rocky Dirt Material

For additional blending of the ground into the walls, I made a few individual rock chunks and pieces. I made one larger chunk of grouped rocks as well as additional smaller rocks that I scattered throughout the space. This helped enforce the illusion of the normal mapped rocks on the terrain and helped to blend the larger wall rock shapes to the dirt on the ground.

For the tire tracks I sculpted some tracks in zbrush and did some editing to the final normal map in Photoshop with some dirt normal map overlays. Then I created my diffuse and the other maps I needed to complete the material for use in Unreal. All of the maps tile from top to bottom so it would be seamless along the spline meshes strung together. I also created an alpha mask to cut out the deeper tracks from the blending ground texture.

Next, I made a subdivided mesh in Maya that I would use to map the tracks to. This mesh would also be used in the scene on a spline to deform and lay on top of the landscape. I then placed the spline throughout the cave and snapped the spline to the landscape using some of the tools Unreal has for controlling the falloff and amount to move the spline or landscape under the spline.

With the alpha mask texture applied on the material as a mask type material, I noticed there was a harsh blend or cut sometimes between the surfaces when the colors or normal map shapes didn’t match up between the tracks and the landscape. When I tried a transparent material blend I lost a lot of the normal and material response I had previously received from the masked type material.

In doing some research I found a node that served my goal of fixing this issue, the dither opacity node. This node was released in version 4.11 and provides a subtle blend for a masked material type and emulates transparency with some noise to fake the blend. There are a few quirks as it can “sizzle” or minor ghosting issues but if used correctly or with noisier textures the ill effects are easily hidden. Since I was using this on the ground it was easily disguised in with the dirt, rocks, and ground blends.