class MGeometryManager

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public members:

enum	GeometricShape Default geometry shapes kDefaultSphere Sphere with radius 1, centered at 0,0,0. kDefaultPlane Plane with width and height of 1, centered at 0,0,0. Assuming "Y-Up" orientation: width = x-axis, and height = y-axis. kDefaultCube Cube with width, height and depth of 1, centered at 0,0,0.
static MGeometry	getGeometry ( const MDagPath & shape, const MGeometryRequirements & requirements, MObject * components = NULL)
static MGeometryList *	referenceDefaultGeometry (const MGeometryManager::GeometricShape geomShape, const MGeometryRequirements & requirements)
static MStatus	dereferenceDefaultGeometry ( MGeometryList * data)

Documentation

Description

The MGeometryManager provides an interface for loading and using hardware textures.

Functions

MGeometry MGeometryManager:: getGeometry ( const MDagPath & shape, const MGeometryRequirements & requirements, MObject * components)

Description

Access the Geometry cache for a shape.

Arguments

• shape the surface
• requirements the surface data you want in the cache. Attempting to access cache data not included in the requirements will fail.
• components an optional component group, for accessing a sub-selection of faces (e.g. the faces assigned to a material)

Return Value

• the cached geometry

MGeometryList * MGeometryManager:: referenceDefaultGeometry (const MGeometryManager::GeometricShape geomShape, const MGeometryRequirements & requirements)

Description

Obtain a reference to geometry for some "default" shapes maintained by the manager such that the geometry returned will match a set of geometric requirements (MGeometryRequirements). The actual form is a geometric iterator (MGeometryList), which can be used to iterate over the internal data kept (MGeometry).

Note that all data is assumed to be "read-only", as the data is not owned by the caller. To maintain proper reference counting of internal data, the user must "deference" the data when no longer using it via the MGeometryManager::dereferenceGeometry() calls. It is recommended to immediately dereference the data after each use. There is negligable overhead to reference and dereference data in this manner.

Available default shapes include:

• A polygonal sphere : Sphere has radius of 1 and is centered at the origin (0,0,0) in object space.
• A polygonal cube : Cube has dimensions of 1 and is centered at the origin (0,0,0) in object space.
• A polygonal plane : Plane has dimensions of 1 is centered at the origin (0,0,0) in object space. Assuming "Y-Up" orientation, the width is the along the x-axis and the height is along the y-axis.

The following is an example usage via a hardware shader plugin for swatch rendering:

	{
		// Set up a NULL path	
		MDagPath path;						

		// Get the requirements from the hardware shader
		MGeometryRequirements requirements;
		populateRequirements(path, requirements);

		// Ask for a default sphere
		MGeometryManager::GeometricShape shape = MGeometryManager::kDefaultSphere;
		MGeometryList* geomIter = MGeometryManager::referenceDefaultGeometry(shape, requirements);

		if(geomIter == NULL) {
			return MStatus::kFailure;
		}

		// Set up where to draw to ....

		// Now draw using the geometry iterator returned.
		//
		for( ; !geomIter->isDone(); geomIter->next())
		{
			// Get the current geometry
			MGeometry& geometry = geomIter->geometry(MGeometryList::kNone);

			// Get the current object to world matrix
			const MMatrix& mtm = geomIter->objectToWorldMatrix();

			glMatrixMode(GL_MODELVIEW);
			glLoadMatrixd(mtm[0]);

			// Get some data tro draw
			MGeometryPrimitive primitives = geometry.primitiveArray(0);
			const MGeometryData pos = geometry.position();
			const MGeometryData normal = geometry.normal();

			if (pos.data() != NULL && primitives.data() != NULL) 
			{
				// Set up position and normals for drawing
				//
				glEnableClientState(GL_VERTEX_ARRAY);
				glVertexPointer(3, GL_FLOAT, 0, (float*) pos.data());

				if (normal.data()) {
					glEnableClientState(GL_NORMAL_ARRAY);
					glNormalPointer(GL_FLOAT, 0,  normal.data());
				}

				// Draw with the current indexing structure 
				MGeometryPrimitive primitives = geometry.primitiveArray(0);
				glDrawElements(GL_TRIANGLES, primitives.elementCount(), GL_UNSIGNED_INT, primitives.data());

				glDisableClientState(GL_VERTEX_ARRAY);
				if (normal.data()) 
					glDisableClientState(GL_NORMAL_ARRAY);
			}
		}

		// Now dereference the geometry iterator used.
		MGeometryManager::dereferenceDefaultGeometry(geomIter);
	}


	

Arguments

• geomShape : Desired geometry shape.
• requirements : Geometry requirements (MGeometryRequirements).

Return Value

• A pointer to a geometry iterator (MGeometryList), which contains a reference to the geometric data (MGeometry). The MGeometry information which tries to match the requirements passed in. ( e.g. position, normal, texture coordinates, tangents, and binormals etc). It can be assumed that all data is floating point such that:
  • Positions are 3 float (x,y,z) positions
  • Normals are 3 float (x,y,z) vectors.
  • Texture coordinates are 2 float (u,v) tuples.
  • Tangents are 3 float (x,y,z) vectors.
  • Binormals are 3 float (x,y,z) vectors.

MStatus MGeometryManager:: dereferenceDefaultGeometry ( MGeometryList * geomIterator)

Description

This is the companion method to referenceDefaultGeometry() and must always be called immediately after usage of data supplied by the reference call.

This call simply maintains proper internal state for any data used.

Arguments

• geomIterator : The geometry iterator returned from referenceDefaultGeometry().

Return Value MStatus::kSuccess if successfull, otherwise MStatus::kFailure.

This class has no child classes.