Preparing Your Scene
This tutorial walks you through the best way to prepare a scene for Previz as well as a checklist for exporting scenes.
Apr 14th 2020
Apr 14th 2020
This simple project simulates a stage with two tall screens (seen here in purple), an assembly of several smaller screens as a main screen (screen_main - seen here in green) and a few meshes working as props. The scene will also hold some basic material and lights.
A Previz scene consists of a collection of:
- Objects (3D meshes) representing the physical elements of a scenes (screens, stages, buildings, props...)
- Mappings (UV sets) describing the different ways objects are textured
- Assets (images and videos)
- Lights (spot and point)
Our sample project has several different UV maps:
- direct_b which fully maps a 1920x1080px asset to the centre screen (b)
- direct_a + direct_c, side screens which have a respective direct map that textures a 780x1080px to the sides
- planar_all which is an orthographic projection from front-of-house to all the screens. As such, this mapping exists all screen meshes: a, b, c
All stage props each have a UV map: UV_prop. It will be used within Previz to apply a static texture to the props which all of these meshes share (consider the props texture space above). In this example an Ambient Occlusion pass has been baked into a texture, but any other techniques like Image Based Lighting can be used to enhance the look of those static objects.
Note: mappings are coming into Previz as number indexed UV maps. Collective mappings such are the above planar_all are grouped in Previz.
Simplifying The Scene
In general, it is better to limit the number of meshes as much as possible by joining related parts together: the less meshes, the less default mappings have to be set in Previz.
Here, we could have had two different meshes for each side screen. But as both screens are the same and have exactly the same mappings, they form a well defined logical group of objects: it makes sense to join them to a single mesh.
Keep an eye on the number of vertices of your meshes: the bigger the mesh, the lower Frame Per Seconds Previz will reach. Exports from CAD software, LIDAR and point clouds are notoriously generating over-complex objects. Try to simplify your geometries as much as possible. CAD and LIDAR exports also tend to generate non-manifold meshes, orphan vertices that don't describe polygons, inner-faces and sometimes unusable overlapping UV sets. Be sure to clean those models: usually they won't affect the look of your scene, so it is not obvious at first that they have an impact on performances.
Previz expects the center of the scene to be located at the origin of the coordinate system: make sure to recenter your scene around the (0, 0, 0) coordinate.
Checklist before exporting to Previz
- Geometries from CAD / LIDAR have:No orphan verticesOnly manifold objectsNo inner faces
- Objects are logically combined and grouped into few meshes
- Meshes and scene objects (lights) have unique names
- UV sets are properly named:
- Mapping unique to a single mesh have an unique name
- Mappings shared between several meshes have the exact same name
- Optional: prop meshes have baked textures, normals and AO to simplify the scene
After checking these points, the scene is ready to be exported to Previz.
- In Blender 2.8 and above; ensure glTF support is turned on. Settings > Addons >glTF
- Export glTF via the menu and ensure to save as glb (binary):
- Apply your selection or full scene as needed
- Include camera and lights as needed
- Keep standard transforms (+Y is up)
- Apply or disregard modifiers as needed
- Include UVs, Material
- Pack your images (textures) as required or upload them later
- Do not use compression
- Turn off animation, shape keys + skinning
- Save to your file name (consider using version numbers for ease of use)
- In Previz upload your file.
The following link contain project files for this tutorial as well as the textures used. The zipped export includes the scene in three formats:
- a .blend file
- an .fbx file
- a .glb file