Panda3D
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SceneGraphReducer Class Reference

An interface for simplifying ("flattening") scene graphs by eliminating unneeded nodes and collapsing out unneeded state changes and transforms. More...

Public Types

enum  AttribTypes {
  TT_transform = 1, TT_color = 2, TT_color_scale = 4, TT_tex_matrix = 8,
  TT_clip_plane = 16, TT_cull_face = 32, TT_apply_texture_color = 64, TT_other = 128
}
 
enum  CollectVertexData {
  CVD_name = 1, CVD_model = 2, CVD_transform = 4, CVD_avoid_dynamic = 8,
  CVD_one_node_only = 16, CVD_format = 32, CVD_usage_hint = 64, CVD_animation_type = 128
}
 
enum  CombineSiblings { CS_geom_node = 1, CS_within_radius = 2, CS_other = 4, CS_recurse = 8 }
 
enum  MakeNonindexed { MN_composite_only = 1, MN_avoid_animated = 2, MN_avoid_dynamic = 4 }
 

Public Member Functions

 __init__ (GraphicsStateGuardianBase gsg)
 
 __init__ (const SceneGraphReducer)
 
 applyAttribs (PandaNode node, const AccumulatedAttribs attribs, int attrib_types, GeomTransformer transformer)
 This flavor of apply_attribs() can be called recursively from within another flatten process (e.g. More...
 
 applyAttribs (PandaNode node, int attrib_types)
 Walks the scene graph, accumulating attribs of the indicated types, applying them to the vertices, and removing them from the scene graph. More...
 
bool checkLiveFlatten (PandaNode node)
 In a non-release build, returns false if the node is correctly not in a live scene graph. More...
 
 clearGsg ()
 Specifies that no particular GraphicsStateGuardian will be used to guide the optimization. More...
 
int collectVertexData (PandaNode root, int collect_bits)
 Collects all different GeomVertexData blocks that have compatible formats at this node and below into a single, unified block (or at least multiple larger blocks). More...
 
 decompose (PandaNode root)
 Calls decompose() on every GeomNode at this level and below. More...
 
int flatten (PandaNode root, int combine_siblings_bits)
 Simplifies the graph by removing unnecessary nodes and nodes. More...
 
float getCombineRadius ()
 Returns the radius that is used in conjunction with CS_within_radius. More...
 
GraphicsStateGuardianBase getGsg ()
 Returns the particular GraphicsStateGuardian that this object will attempt to optimize to. More...
 
int makeCompatibleFormat (PandaNode root, int collect_bits)
 Walks through the tree at this node and below and unifies the GeomVertexFormat for any GeomVertexData objects that are found, so that all eligible vdatas (according to collect_bits; see collect_vertex_data) will share the same vertex format. More...
 
int makeCompatibleState (PandaNode root)
 Searches for GeomNodes that contain multiple Geoms that differ only in their ColorAttribs. More...
 
int makeNonindexed (PandaNode root, int nonindexed_bits)
 Converts indexed geometry to nonindexed geometry at the indicated node and below, by duplicating vertices where necessary. More...
 
 premunge (PandaNode root, const RenderState initial_state)
 Walks the scene graph rooted at this node and below, and uses the indicated GSG to premunge every Geom found to optimize it for eventual rendering on the indicated GSG. More...
 
int removeColumn (PandaNode root, const InternalName column)
 Removes the indicated data column from any GeomVertexDatas found at the indicated root and below. More...
 
 removeUnusedVertices (PandaNode root)
 Removes any vertices in GeomVertexDatas that are no longer used at this level and below. More...
 
 setCombineRadius (float combine_radius)
 Specifies the radius that is used in conjunction with CS_within_radius to decide whether a subgraph's siblings should be combined into a single node or not. More...
 
 setGsg (GraphicsStateGuardianBase gsg)
 Specifies the particular GraphicsStateGuardian that this object will attempt to optimize to. More...
 
 unify (PandaNode root, bool preserve_order)
 Calls unify() on every GeomNode at this level and below. More...
 

Detailed Description

An interface for simplifying ("flattening") scene graphs by eliminating unneeded nodes and collapsing out unneeded state changes and transforms.

This class is designed so that it may be inherited from and specialized, if needed, to fine-tune the flattening behavior, but normally the default behavior is sufficient.

Member Enumeration Documentation

◆ AttribTypes

Enumerator
TT_transform 
TT_color 
TT_color_scale 
TT_tex_matrix 
TT_clip_plane 
TT_cull_face 
TT_apply_texture_color 
TT_other 

◆ CollectVertexData

Enumerator
CVD_name 

If set, two GeomVertexDatas with different names will not be collected together.

CVD_model 

If set, a ModelNode begins a subgraph of nodes whose GeomVertexDatas will not be collected with nodes outside the subgraph.

CVD_transform 

If set, a non-identity transform begins a subgraph of nodes whose GeomVertexDatas will not be collected with nodes outside the subgraph.

CVD_avoid_dynamic 

If set, GeomVertexDatas with any usage_hint other than UH_static will not be collected with any other Geoms in a different GeomNode. However, two different dynamic Geoms within the same node might still be collected together.

CVD_one_node_only 

If set, only those GeomVertexDatas within the same node might be collected together.

CVD_format 

If set, two GeomVertexDatas with different formats will not be collected together. If not set, GeomVertexDatas of different formats may be combined by expanding all GeomVertexDatas to the union of all defined columns.

CVD_usage_hint 

If set, two GeomVertexDatas with different usage hints (for instance, UH_static vs. UH_dynamic) will not be collected together.

CVD_animation_type 

If set, GeomVertexDatas with unanimated vertices will not be combined with GeomVertexDatas with animated vertices.

◆ CombineSiblings

Enumerator
CS_geom_node 
CS_within_radius 
CS_other 
CS_recurse 

◆ MakeNonindexed

Enumerator
MN_composite_only 

If set, only composite primitives such as tristrips and trifans will be made nonindexed; simple primitives such as triangles will be left indexed.

MN_avoid_animated 

If set any GeomVertexData with any animation indication will not be adjusted, whether the animation is to be performed on the CPU or on the graphics pipe.

MN_avoid_dynamic 

If set, any GeomVertexData or Geom with a usage_hint other than UH_static will not be made nonindexed.

Member Function Documentation

◆ __init__() [1/2]

__init__ ( GraphicsStateGuardianBase  gsg)

◆ __init__() [2/2]

__init__ ( const  SceneGraphReducer)

◆ applyAttribs() [1/2]

applyAttribs ( PandaNode  node,
const AccumulatedAttribs  attribs,
int  attrib_types,
GeomTransformer  transformer 
)

This flavor of apply_attribs() can be called recursively from within another flatten process (e.g.

from PandaNode::apply_attribs_to_vertices()). The parameters were presumably received from a parent SceneGraphReducer object.

◆ applyAttribs() [2/2]

applyAttribs ( PandaNode  node,
int  attrib_types 
)

Walks the scene graph, accumulating attribs of the indicated types, applying them to the vertices, and removing them from the scene graph.

This has a performance optimization benefit in itself, but is especially useful to pave the way for a call to flatten() and greatly improve the effectiveness of the flattening operation.

Multiply instanced geometry is duplicated before the attribs are applied.

Of course, this operation does make certain dynamic operations impossible.

◆ checkLiveFlatten()

bool checkLiveFlatten ( PandaNode  node)

In a non-release build, returns false if the node is correctly not in a live scene graph.

(Calling flatten on a node that is part of a live scene graph, for instance, a node somewhere under render, can cause problems in a multithreaded environment.)

If allow_live_flatten is true, or in a release build, this always returns true.

◆ clearGsg()

clearGsg ( )

Specifies that no particular GraphicsStateGuardian will be used to guide the optimization.

The SceneGraphReducer will instead use config variables such as max-collect-vertices and max-collect-indices.

◆ collectVertexData()

int collectVertexData ( PandaNode  root,
int  collect_bits 
)

Collects all different GeomVertexData blocks that have compatible formats at this node and below into a single, unified block (or at least multiple larger blocks).

This is intended to reduce rendering overhead incurred by switching vertex buffers. It can also make a subsequent call to unify() much more effective than it would have been otherwise.

The set of bits passed in collect_bits indicates which properties are used to differentiate GeomVertexData blocks. If it is 0, then more blocks will be combined together than if it is nonzero.

◆ decompose()

decompose ( PandaNode  root)

Calls decompose() on every GeomNode at this level and below.

There is usually no reason to call this explicitly, since unify() will do this anyway if it needs to be done. However, calling it ahead of time can make that future call to unify() run a little bit faster.

This operation has no effect if the config variable preserve-triangle- strips has been set true.

◆ flatten()

int flatten ( PandaNode  root,
int  combine_siblings_bits 
)

Simplifies the graph by removing unnecessary nodes and nodes.

In general, a node (and its parent node) is a candidate for removal if the node has no siblings and the node has no special properties.

If combine_siblings_bits is nonzero, some sibling nodes (according to the bits set in combine_siblings_bits) may also be collapsed into a single node. This will further reduce scene graph complexity, sometimes substantially, at the cost of reduced spatial separation.

Returns the number of nodes removed from the graph.

◆ getCombineRadius()

float getCombineRadius ( )

Returns the radius that is used in conjunction with CS_within_radius.

See set_combine_radius().

◆ getGsg()

Returns the particular GraphicsStateGuardian that this object will attempt to optimize to.

See set_gsg().

◆ makeCompatibleFormat()

int makeCompatibleFormat ( PandaNode  root,
int  collect_bits 
)

Walks through the tree at this node and below and unifies the GeomVertexFormat for any GeomVertexData objects that are found, so that all eligible vdatas (according to collect_bits; see collect_vertex_data) will share the same vertex format.

This will add unused columns where necessary to match formats. It can result in suboptimal performance if used needlessly.

There is usually no reason to call this explicitly, since collect_vertex_data() will do this anyway if it has not been done already. However, calling it ahead of time can make that future call to collect_vertex_data() run a little bit faster.

The return value is the number of vertex datas modified.

◆ makeCompatibleState()

int makeCompatibleState ( PandaNode  root)

Searches for GeomNodes that contain multiple Geoms that differ only in their ColorAttribs.

If such a GeomNode is found, then all the colors are pushed down into the vertices. This makes it feasible for the geoms to be unified later.

◆ makeNonindexed()

int makeNonindexed ( PandaNode  root,
int  nonindexed_bits 
)

Converts indexed geometry to nonindexed geometry at the indicated node and below, by duplicating vertices where necessary.

The parameter nonindexed_bits is a union of bits defined in SceneGraphReducer::MakeNonindexed, which specifes which types of geometry to avoid making nonindexed.

◆ premunge()

premunge ( PandaNode  root,
const RenderState  initial_state 
)

Walks the scene graph rooted at this node and below, and uses the indicated GSG to premunge every Geom found to optimize it for eventual rendering on the indicated GSG.

If there is no GSG indicated for the SceneGraphReducer, this is a no-op.

This operation will also apply to stashed children.

◆ removeColumn()

int removeColumn ( PandaNode  root,
const InternalName  column 
)

Removes the indicated data column from any GeomVertexDatas found at the indicated root and below.

Returns the number of GeomNodes modified.

◆ removeUnusedVertices()

removeUnusedVertices ( PandaNode  root)

Removes any vertices in GeomVertexDatas that are no longer used at this level and below.

This requires remapping vertex indices in all of the GeomPrimitives, to remove holes in the GeomVertexDatas. It is normally not necessary to call this explicitly.

◆ setCombineRadius()

setCombineRadius ( float  combine_radius)

Specifies the radius that is used in conjunction with CS_within_radius to decide whether a subgraph's siblings should be combined into a single node or not.

If the CS_within_radius bit is included in the combine_siblings_bits parameter passed to flatten, than any nodes whose bounding volume is smaller than the indicated radius will be combined together (as if CS_other were set).

◆ setGsg()

setGsg ( GraphicsStateGuardianBase  gsg)

Specifies the particular GraphicsStateGuardian that this object will attempt to optimize to.

The GSG may specify parameters such as maximum number of vertices per vertex data, max number of vertices per primitive, and whether triangle strips are preferred. It also affects the types of vertex column data that is created by premunge().

◆ unify()

unify ( PandaNode  root,
bool  preserve_order 
)

Calls unify() on every GeomNode at this level and below.

This attempts to reduce the total number of individual Geoms and GeomPrimitives by combining these objects wherever possible. See GeomNode::unify().