Pre-transforms and batches up meshes for efficient use as static geometry in a scene.
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Pre-transforms and batches up meshes for efficient use as static geometry in a scene.
Modern graphics cards (GPUs) prefer to receive geometry in large batches. It is orders of magnitude faster to render 10 batches of 10,000 triangles than it is to render 10,000 batches of 10 triangles, even though both result in the same number of on-screen triangles.
- Therefore it is important when you are rendering a lot of geometry to batch things up into as few rendering calls as possible. This class allows you to build a batched object from a series of entities in order to benefit from this behaviour. Batching has implications of it's own though:
- Batched geometry cannot be subdivided; that means that the whole group will be displayed, or none of it will. This obivously has culling issues.
- A single world transform must apply to the entire batch. Therefore once you have batched things, you can't move them around relative to each other. That's why this class is most useful when dealing with static geometry (hence the name). In addition, geometry is effectively duplicated, so if you add 3 entities based on the same mesh in different positions, they will use 3 times the geometry space than the movable version (which re-uses the same geometry). So you trade memory and flexibility of movement for pure speed when using this class.
- A single material must apply for each batch. In fact this class allows you to use multiple materials, but you should be aware that internally this means that there is one batch per material. Therefore you won't gain as much benefit from the batching if you use many different materials; try to keep the number down.
- In order to retain some sort of culling, this class will batch up meshes in localised regions. The size and shape of these blocks is controlled by the SceneManager which constructs this object, since it makes sense to batch things up in the most appropriate way given the existing partitioning of the scene.
- The LOD settings of both the Mesh and the Materials used in constructing this static geometry will be respected. This means that if you use meshes/materials which have LOD, batches in the distance will have a lower polygon count or material detail to those in the foreground. Since each mesh might have different LOD distances, during build the furthest distance at each LOD level from all meshes
in that region is used. This means all the LOD levels change at the same time, but at the furthest distance of any of them (so quality is not degraded). Be aware that using Mesh LOD in this class will further increase the memory required. Only generated LOD is supported for meshes.
- There are 2 ways you can add geometry to this class; you can add Entity objects directly with predetermined positions, scales and orientations, or you can add an entire SceneNode and it's subtree, including all the objects attached to it. Once you've added everything you need to, you have to call build() the fix the geometry in place.
- Note
- This class is not a replacement for world geometry (
- See also
- SceneManager::setWorldGeometry). The single most efficient way to render large amounts of static geometry is to use a SceneManager which is specialised for dealing with that particular world structure. However, this class does provide you with a good 'halfway house' between generalised movable geometry (Entity) which works with all SceneManagers but isn't efficient when using very large numbers, and highly specialised world geometry which is extremely fast but not generic and typically requires custom world editors.
- You should not construct instances of this class directly; instead, cal SceneManager::createStaticGeometry, which gives the SceneManager the option of providing you with a specialised version of this class if it wishes, and also handles the memory management for you like other classes.
- Note
- Warning: this class only works with indexed triangle lists at the moment, do not pass it triangle strips, fans or lines / points, or unindexed geometry.
| virtual void Ogre::StaticGeometry::setCastShadows |
( |
bool |
castShadows | ) |
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|
virtual |
Sets whether this geometry should cast shadows.
No matter what the settings on the original entities, the StaticGeometry class defaults to not casting shadows. This is because, being static, unless you have moving lights you'd be better to use precalculated shadows of some sort. However, if you need them, you can enable them using this method. If the SceneManager is set up to use stencil shadows, edge lists will be copied from the underlying meshes on build. It is essential that all meshes support stencil shadows in this case.
- Note
- If you intend to use stencil shadows, you must set this to true before calling 'build' as well as making sure you set the scene's shadow type (that should always be the first thing you do anyway). You can turn shadows off temporarily but they can never be turned on if they were not at the time of the build.
| virtual void Ogre::StaticGeometry::setRegionDimensions |
( |
const Vector3 & |
size | ) |
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inlinevirtual |
Sets the size of a single region of geometry.
This method allows you to configure the physical world size of each region, so you can balance culling against batch size. Entities will be fitted within the batch they most closely fit, and the eventual bounds of each batch may well be slightly larger than this if they overlap a little. The default is Vector3(1000, 1000, 1000).
- Note
- Must be called before 'build'.
- Parameters
-
| size | Vector3 expressing the 3D size of each region. |
| virtual void Ogre::StaticGeometry::setOrigin |
( |
const Vector3 & |
origin | ) |
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|
inlinevirtual |
Sets the origin of the geometry.
This method allows you to configure the world centre of the geometry, thus the place which all regions surround. You probably don't need to mess with this unless you have a seriously large world, since the default set up can handle an area 1024 * mRegionDimensions, and the sparseness of population is no issue when it comes to rendering. The default is Vector3(0,0,0).
- Note
- Must be called before 'build'.
- Parameters
-
| origin | Vector3 expressing the 3D origin of the geometry. |
Inheritance diagram for Ogre::StaticGeometry:
1.9.1