OK, I get what you are saying, you just want a preview render to see the motion. In Vue, set your render quality to preview, not boadcast or anything like that. Drop your frame rate to between 5 and 8 frames per second, instead of the normal 25 or 30. Delete all lights except the sun, and turn of shadows on your objects. If you are using Vue 5 Infinite, you can also decimate the meshes for fewer polygons. Set the size of your render down as well. If you just want to see the motion, you don't need a big size. I think that turning up the compression may actually slow it down, as it has to calculate the compression for every frame. Just render to straight image files, jpg, with no compression. Rendering time increases proportionally with an increase in the amount of polygons, lights, shadows, image size, and number of objects. If there are objects in the scene that you don't need to see in the preview, I think there is a hide from render option as well (I am not at my Vue PC to check).

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