SoBufferedShape Class Reference
[Shapes]
Node to render geometry stored in SoBufferObject objects.
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#include <Inventor/nodes/SoBufferedShape.h>
Detailed Description
Node to render geometry stored in SoBufferObject objects.
SoBufferedShape is useful to manage the rendering of large geometry, provide application control over where the data is stored (CPU or GPU) and to integrate rendering with the Open Inventor computing framework (through the SoBufferObject classes).
SoBufferedShape provides fields for:
- Vertices
- Indices (optional)
- Colors (optional)
- Normals (optional)
- Texture coordinates (optional)
In this sense it is similar to the SoVertexProperty node, but SoVertexProperty is just a property node. SoBufferedShape also does the rendering of the shape. Properties that are not specified are taken from the traversal state (e.g. colors) or computed (e.g. normals).
SoBufferedShape can render many types of geometric primitives including points, lines, quads and triangles. (A single type must be specified per instance of SoBufferedShape.) You specify the type of primitive in the SoSFEnum field shapeType.
SoBufferedShape can render multiple primitives of the same type. You can specify the number of vertices (or indices if provided) to use for each primitive in the SoMFInt32 field numVertices (similar to SoFaceSet).
You can also use the primitive restart feature to define multiple indexed strip shapes, for example TRIANGLE_STRIP or LINE_STRIP. The end of each primitive is marked by a special index value in the index buffer and this value can be specified in the primitiveRestartValue field. The behavior is similar to the "-1" value that can be used in Open Inventor indexed shape nodes like SoIndexedFaceSet, but is implemented on the GPU.
NOTE:
- Primitive restart must be explicitly enabled using the primitiveRestartEnabled field.
- Check availability of primitive restart using SoShape::isPrimitiveRestartAvailable().
The geometry and its attributes must be stored in buffer objects (see SoBufferObject). The buffer objects can be SoGpuBufferObjects stored directly on the graphics board or SoCpuBufferObjects stored in system memory. This allows the application to control what data is stored where.
In the general case, when the underlying buffer object is modified using the SoBufferObject API (setSize, map, memcpy, memset), the containing SoSFBufferObject field needs to be notified using touch() in order for Open Inventor to take this modification into account. If touch() is not called, there is no guarantee that the modifications will be visible on the next rendering.
If the application needs to frequently modify the values of an SoBufferObject, calling touch() on the field can result in an undesirable decrease in performance. Instead, it is recommended to use an instance of SoGpuBufferObject and set the shapeUsage field to DYNAMIC. These settings guarantee that this buffer data will be used directly for rendering, and eliminate the need to call touch() on the field. It also guarantees that modifications to the buffer done by shaders will be properly taken into account.
If lighting is enabled (there is no SoLightModel node or the model field of the SoLightModel is set to PHONG) and the normalBuffer field is not set, then Open Inventor will automatically compute normal vectors, but only in some cases (see Limitations section). Normal generation is affected by the creaseAngle field of the SoShapeHints node, but only if the vertices are NOT indexed (indexBuffer field is not set). If the vertices are indexed the creaseAngle is forced to PI, creating a smooth surface rendering. If the application needs to render sharp edges on a shape, either compute normal vectors and set the normalBuffer field or do not use the indexBuffer field. It is possible to disable normal generation (if for example the normals are generated by a geometry shader) by setting the useNormalsGenerator field to FALSE. If no normal vectors are specified or generated, and lighting is enabled, the primitive may not be rendered correctly.
SoBufferedShape provides fields to describe the content of each buffer, e.g. the data type and number of components in each buffer, as well as how to access the buffers, e.g. the offset into the buffer and "stride" separating data values in the buffer. The default values for offset and stride assume that the vertices, normals, etc are each in a separate buffer. However setting appropriate offset and stride allows, for example, vertices and normals to be interleaved in a single buffer. In this case the same buffer would be set into both the vertexBuffer and normalBuffer fields.
To disable computing the bounding box, which can take a long time with very large geometry, use the SoBBox node to specify a pre-computed bounding box.
Limitations
- Transparency:
If there is no color buffer, making the entire shape transparent using an SoMaterial node works as usual. However if there is a color buffer with RGBA values, note that Open Inventor does not currently check the color buffer for transparency (alpha values < 1). So in this case the SoBufferedShape will not be considered transparent geometry (even if there are alpha values < 1) and may not be rendered correctly. You can force Open Inventor to handle the shape as transparent geometry by putting an SoMaterial node with non-zero transparency before it in the scene graph.
- Normal generation:
If lighting is enabled and the normalBuffer field is not set, then Open Inventor will automatically compute normal vectors, but only in some cases. Automatic generation of normal vectors is ONLY enabled when:- The vertexComponentsCount field is set to 2 or 3,
- The primitiveRestartEnabled field is set to FALSE (default), and
- The primitives are TRIANGLES, TRIANGLE_STRIP or QUADS.
Note: The crease angle (see SoShapeHints) is not used by the normal generator if the vertices are indexed. If the application needs to render sharp edges on a shape, either compute normal vectors and set the normalBuffer field or do not use the indexBuffer field.
- SoGetPrimitiveCountAction:
When using the primitive restart feature, the triangle/line count returned by the SoGetPrimitiveCountAction will not be accurate.
- Concave polygons:
Unlike (for example) SoFaceSet, SoBufferedShape does NOT automatically tesselate concave or complex polygons. Such primitives may not be rendered correctly.
- SoWriteAction:
SoBufferedShape can be saved to and restored from a .iv file just like any other Open Inventor node. However, during the read operation any GPU buffer objects (SoGpuBufferObject) in the file will be created as CPU buffers (SoCpuBufferObject).
- Material binding (etc):
SoBufferedShape effectively only supports per-vertex and per-vertex-indexed binding of materials, normals and texture coordinates using the values found in its own buffers.
Example using CPU buffer:
// Result should be similar to SoLineSet example in PG-GettingStarted.pdf. // This example does not show any of the advantages of using SoBufferedShape, // just the simplest possible setup and usage. // Coordinate data const float vertices[][3] = { 1,0.5,0, 0,1,0, -1,0.5,0, -1,-1,0, 1,-1,0, 1,0,0, -1,0,0, -1,-1.5,0, 1,-1.5,0 }; const int numVerts[] = {3, 4, 2}; const int NUM_COORDS = sizeof(vertices) / sizeof(SbVec3f); const int NUM_COUNTS = sizeof(numVerts) / sizeof(int); // Wrap coordinate array in a CPU buffer object SoRef<SoCpuBufferObject> vertBuf = new SoCpuBufferObject( (void*)vertices, NUM_COORDS * sizeof(SbVec3f) ); // Create a buffered shape to render the geometry SoBufferedShape *pShape = new SoBufferedShape; pShape->shapeType = SoBufferedShape::LINE_STRIP; pShape->numVertices.setValues( 0, NUM_COUNTS, numVerts ); pShape->vertexBuffer.setValue( vertBuf.ptr() );
Example using GPU buffer:
// Result should be similar to SoLineSet example in PG-GettingStarted.pdf. // This example does not show any of the advantages of using SoBufferedShape, // just the simplest possible setup and usage. // Coordinate data const float coords[][3] = { 1,0.5,0, 0,1,0, -1,0.5,0, -1,-1,0, 1,-1,0, 1,0,0, -1,0,0, -1,-1.5,0, 1,-1.5,0 }; const int numVerts[] = {3, 4, 2}; const int NUM_COORDS = sizeof(coords) / sizeof(SbVec3f); const int NUM_COUNTS = sizeof(numVerts) / sizeof(int); // Wrap coordinate array in a CPU buffer object SoRef<SoCpuBufferObject> cpuBuffer = new SoCpuBufferObject( (void*)coords, NUM_COORDS * sizeof(SbVec3f) ); // Create a GPU (OpenGL) buffer and load data from CPU buffer SoRef<SoGLContext> glContext = new SoGLContext(true); glContext->bind(); SoRef<SoGpuBufferObject> gpuBuffer = new SoGpuBufferObject( SoGpuBufferObject::STATIC, SoGpuBufferObject::SHARED ); gpuBuffer->setSize ( cpuBuffer->getSize() ); // Set the buffer size (allocate memory) gpuBuffer->memcpy ( cpuBuffer.ptr() ); // Copy data into the buffer glContext->unbind(); // Create a buffered shape node to render the geometry SoBufferedShape *pShape = new SoBufferedShape; pShape->shapeType = SoBufferedShape::LINE_STRIP; pShape->numVertices.setValues( 0, NUM_COUNTS, numVerts ); pShape->vertexBuffer.setValue( gpuBuffer.ptr() );
LIMITATIONS: SoBufferedShape needs a graphic card supporting vertex buffer objects, if not available shape won't be rendered.
FILE FORMAT/DEFAULT
- BufferedShape {
| useNormalsGenerator | TRUE |
| shapeType | TRIANGLES |
| numVertices | 0 |
| vertexBuffer | NULL |
| vertexComponentsCount | 3 |
| vertexComponentsType | SbDataType::FLOAT |
| vertexStride | 0 |
| vertexOffset | 0 |
| normalBuffer | NULL |
| normalComponentsType | SbDataType::FLOAT |
| normalStride | 3 * sizeof(float) |
| normalOffset | 0 |
| indexBuffer | NULL |
| indexType | SbDataType::UNSIGNED_INT32 |
| indexOffset | 0 |
| colorBuffer | NULL |
| colorComponentsType | SbDataType::FLOAT |
| colorStride | 0 |
| colorOffset | 0 |
| colorComponentsCount | 3 |
| texCoordsBuffer | NULL |
| texCoordsComponentsType | SbDataType::FLOAT |
| texCoordsStride | 0 |
| texCoordsOffset | 0 |
| texCoordsComponentsCount | 2 |
| primitiveRestartEnabled | FALSE |
| primitiveRestartValue | -1 |
ACTION BEHAVIOR
- SoGLRenderAction, SoCallbackAction, SoBoundingBoxAction
Do the actual rendering / bounding box computation.
SEE ALSO
SoCpuBufferObject, SoGpuBufferObject, SoBBox
- See related examples:
-
AnimatedShape, BufferedShapePicking, GPUGeometry, InterleavedVertexAttribFeedback, PrimitiveRestart, SimpleVertexAttribFeedback, SoBufferedShape, SoVertexShaderParameter, VertexAttribFeedback
Member Enumeration Documentation
Type of shape that will be rendered.
- Enumerator:
This enum is used to set the shapeUsage field.
Constructor & Destructor Documentation
| SoBufferedShape::SoBufferedShape | ( | ) |
Default constructor.
Member Function Documentation
| static SoType SoBufferedShape::getClassTypeId | ( | ) | [static] |
Returns the type identifier for this class.
Reimplemented from SoShape.
Reimplemented in SoVolumeBufferedShape.
| virtual SoType SoBufferedShape::getTypeId | ( | ) | const [virtual] |
Returns the type identifier for this specific instance.
Reimplemented from SoShape.
Reimplemented in SoVolumeBufferedShape.
Member Data Documentation
Buffer object that contains the (optional) color values.
Default is no buffer. Colors are always per-vertex or per-vertex-indexed. Note: This buffer must be an SoCpuBufferObject or SoGpuBufferObject. (SoGLBufferObject with target = ARRAY_BUFFER is also allowed but not recommended.)
Number of components in each color value.
Default is 3 (i.e. red, green and blue)
SbDataType::DataType type for the color values.
Use enum SbDataType::DataType. Default is SbDataType::FLOAT.
Offset in bytes to the first color value in the buffer.
Default is 0.
Stride in bytes between the first component of two consecutive colors.
Default is 0. e.g: If the colors are composed of 3 float components the stride should be 3 * sizeof(float). If vertices are packed in the same buffer the stride should be 3 * sizeof(float) + 3 * sizeof(float), the second part stands for the extra data padding.
Note: When the values are packed (only color values in the buffer) the value 0 can be used and OpenGL will compute the stride value.
Buffer object that contains the (optional) indices.
Default is no buffer. Note: This buffer must be an SoCpuBufferObject or SoGpuBufferObject. (SoGLBufferObject with target = ARRAY_BUFFER is also allowed but not recommended.)
Offset in bytes to the first index in the buffer.
Default is 0.
SbDataType::DataType type for the indices.
Use enum SbDataType::DataType. Default is SbDataType::UNSIGNED_INT32. Note: Due to OpenGL restrictions, only 3 values are accepted here: SbDataType::UNSIGNED_INT32, SbDataType::UNSIGNED_BYTE or SbDataType::UNSIGNED_SHORT.
Buffer object that contains the (optional) normal vectors.
Default is no buffer. Note: This buffer must be an SoCpuBufferObject or SoGpuBufferObject. (SoGLBufferObject with target = ARRAY_BUFFER is also allowed but not recommended.)
SbDataType::DataType type for the normal vectors.
Use enum SbDataType::DataType. Default is SbDataType::FLOAT.
Offset in bytes to the first normal vector in the buffer.
Default is 0.
Stride in bytes between the first component of two consecutive normals.
Default is 0. e.g: If the normals are composed of 3 float components the stride should be 3 * sizeof(float). If RGB colors are packed in the same buffer the stride should be 3 * sizeof(float) + 3 * sizeof(float), the second part stands for the extra data padding.
Note: When the values are packed (only normals in the buffer) the value 0 can be used and OpenGL will compute the stride value.
Total number of vertices/indices or number of vertices/indices to be used per primitive.
Specifically:
- For the shape types POINTS, LINES, TRIANGLES and QUADS
Only the first value is meaningful and it specifies the number of vertices to be used for rendering. Specifically:- For a list of points: numVertices should be the number of points to be drawn.
- For a list of lines: numVertices should be num_lines * 2 where num_lines is the number of lines to be drawn.
- For a list of quadrangles: numVertices should be num_quads * 4 where num_quads is the number of quadrangles to be drawn.
- For a list of triangles: numVertices should be num_tri * 3 where num_tri is the number of triangles to be drawn.
- For all other types:
The number of values in this field specifies the number of primitives that will be drawn.
Each value in the field specifies the number of vertices (or indices if given) to be used for each primitive.
Enable/disable the primitive restart feature.
Default is FALSE. Primitive restart allows you to define multiple indexed strip shapes using only one index buffer. Each time the primitive restart index is reached a new strip or loop of primitives is emitted. This feature is similar to the "-1" that can be used in the OIV indexed shapes This also means that the availability must be checked before being used
Limitations: Enabling primitive restart disables the normal generator.
NOTE: field available since Open Inventor 8.5Index value for the primitive restart feature.
Default is -1.
NOTE: field available since Open Inventor 8.5Shape type to render.
Use enum Type. Default is TRIANGLES.
Defines the usage of the shape.
Some optimizations can be performed when we know the usage of the shape. Most of the time if the buffer objects attached to the shape are updated on a regular basis prefer using DYNAMIC, otherwise prefer STATIC.
STATIC provides the best performance when the content of the buffer is never modified or modified infrequently.
Use enum Usage. The default value is STATIC.
NOTE: field available since Open Inventor 9.2Buffer objects that contains the (optional) texture coordinates.
Default is no buffer. Note: This buffer must be an SoCpuBufferObject or SoGpuBufferObject. (SoGLBufferObject with target = ARRAY_BUFFER is also allowed but not recommended.)
Number of components in each texture coordinate.
Default is 2 (i.e. S and T)
SbDataType::DataType type for the texture coordinates.
Use enum SbDataType::DataType. Default is SbDataType::FLOAT.
Offset in bytes to the first texture coordinate in the buffer.
Default is 0.
Stride in bytes between the first component of two consecutive texture coordinates.
Default is 0. e.g: If each element is composed of 2 float components the stride should be 2 * sizeof(float). If vertices are packed in the same buffer the stride should be 2 * sizeof(float) + 3 * sizeof(float), the second part stands for the extra data padding.
Note: When the values are packed (only texture coordinates in the buffer) the value 0 can be used and OpenGL will compute the stride value.
Indicates if the node should use the internal normal vector generator if no normals are defined.
Default is TRUE.
This mode is only supported for shapes with float coordinates and 3 components per vertex. It is not supported for the points and the lines.
Disabling the normal generator can be useful if the normals are computed in a shader or if the shaders don't need any normal at all.
Normal generation is affected by the creaseAngle field of SoShapeHints.
Buffer object that contains the vertex data.
Default is no buffer. Note: This buffer must be an SoCpuBufferObject or SoGpuBufferObject. (SoGLBufferObject with target = ARRAY_BUFFER is also allowed but not recommended.)
Number of components in each vertex.
Default is 3 (i.e. X, Y and Z).
SbDataType::DataType for vertices.
Use enum SbDataType::DataType. Default is SbDataType::FLOAT.
Offset in bytes to the first vertex within the buffer.
Default is 0.
Stride in bytes between the first component of two consecutive vertices.
Default is 0. e.g: If the vertices are composed of 3 float components the stride should be 3 * sizeof(float). If RGB colors are packed in the same buffer the stride should be 3 * sizeof(float) + 3 * sizeof(float), the second part stands for the extra data padding.
Note: When the values are packed (only vertices in the buffer) the value 0 can be used and OpenGL will compute the stride value.
The documentation for this class was generated from the following file:
- Inventor/nodes/SoBufferedShape.h