This is very similar to the process I used for my animation "Desert Dawn Drive":
Quote from: undefinedhttps://vimeo.com/353207617
and here's a breakdown of the elements:
Quote from: undefinedhttps://www.youtube.com/watch?reload=9&v=Ifn1X1kGNqo&feature=youtu.be
If you check around 0:16 you'll see the terrain I used in Maya. Sections of the terrain are higher-rez than others and I used tiling with my custom Mel script to split the imported micro exports from Terragen into foreground and background layers.
As you can see, the terrain in the foreground where the car passes over is not as detailed as the Terragen render, but works just fine for casting shadows. Also, as Oshyan mentions, the terrain color maps are nowhere near as detailed as Terragen, but for the purposes of bouncing GI onto the Maya vehicle, they work ok.
I could have used more tiling and higher-rez maps to import terrain textures into Maya, but this was a good trade off between speed, memory and quality. As Matt mentions, add the Surface Diffuse Colour (before lighting) render element (if you have the Professional version) to get the diffuse albedo with no lighting baked in.
Quote from: Matt on May 25, 2017, 05:32:55 PMOr perhaps you can bring the object into Terragen to cast the shadow, and then it's going to be correct.
You can do that, but depending on your animation your shadows won't be motion blurred as imported obj won't render with motion blur.
My solution was to render a shadow matte from Maya (using Arnold) (at 0:18 in the video) - I used that in a composite to matte out the direct light in the Terragen render:
The TG render had tgSurfDirectDiff and tgSurfIndirectDiff render elements turned on and the shadow pass matted out the tgSurfDirectDiff, this way the composited shadow matches the Terragen shadows exactly. With Arnold, there was an added AOV from the shadow pass that rendered the bounce from the vehicle onto the terrain so that could be added to the terrain render also.
To get the Terragen lighting into Maya, I rendered a spherical camera from roughly the position of the animation and added three render elements:
Surface Direct
Surface Indirect
Atmosphere Direct
Atmosphere Indirect
If you add these together in a compositing package but omit the Surface Emission (Luminosity) render element you basically get the ambient light from the Terragen scene. You can then add a Direct light in 3dsMax to restore the sun direct light. I wrote a script to get the position of the Terragen sun based on the hotspot in the emission map and the postion of the shadows matched very accurately, but this can be done manually also.