From Ogre Wiki

You could always generate a sphere in your favorite modeller, but given the nature of some of the Ogre exporters, it's not always so easy.

The following code snippet will make a sphere, making full use of hardware vertex and index buffers for performance.

Original credit for this code goes to mcspy0312 from a post of his on the forums, but it looks like he got it from elsewhere too. His initial code was for a "sky sphere," with the faces pointing inwards. I modified it so that the faces had an outwards orientation and fixed a bug in the texture coordinate code.

C# version is also available in MOGRE ManualSphereMeshes.

If you have a screenshot of a sphere, please upload and add it.

Snippet

This code creates a sphere mesh with the given name:

void createSphere(const std::string& strName, const float r, const int nRings = 16, const int nSegments = 16)
{
	MeshPtr pSphere = MeshManager::getSingleton().createManual(strName, ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
	SubMesh *pSphereVertex = pSphere->createSubMesh();

	pSphere->sharedVertexData = new VertexData();
	VertexData* vertexData = pSphere->sharedVertexData;

	// define the vertex format
	VertexDeclaration* vertexDecl = vertexData->vertexDeclaration;
	size_t currOffset = 0;
	// positions
	vertexDecl->addElement(0, currOffset, VET_FLOAT3, VES_POSITION);
	currOffset += VertexElement::getTypeSize(VET_FLOAT3);
	// normals
	vertexDecl->addElement(0, currOffset, VET_FLOAT3, VES_NORMAL);
	currOffset += VertexElement::getTypeSize(VET_FLOAT3);
	// two dimensional texture coordinates
	vertexDecl->addElement(0, currOffset, VET_FLOAT2, VES_TEXTURE_COORDINATES, 0);
	currOffset += VertexElement::getTypeSize(VET_FLOAT2);

	// allocate the vertex buffer
	vertexData->vertexCount = (nRings + 1) * (nSegments+1);
	HardwareVertexBufferSharedPtr vBuf = HardwareBufferManager::getSingleton().createVertexBuffer(vertexDecl->getVertexSize(0), vertexData->vertexCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY, false);
	VertexBufferBinding* binding = vertexData->vertexBufferBinding;
	binding->setBinding(0, vBuf);
	float* pVertex = static_cast<float*>(vBuf->lock(HardwareBuffer::HBL_DISCARD));

	// allocate index buffer
	pSphereVertex->indexData->indexCount = 6 * nRings * (nSegments + 1);
	pSphereVertex->indexData->indexBuffer = HardwareBufferManager::getSingleton().createIndexBuffer(HardwareIndexBuffer::IT_16BIT, pSphereVertex->indexData->indexCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY, false);
	HardwareIndexBufferSharedPtr iBuf = pSphereVertex->indexData->indexBuffer;
	unsigned short* pIndices = static_cast<unsigned short*>(iBuf->lock(HardwareBuffer::HBL_DISCARD));

	float fDeltaRingAngle = (Math::PI / nRings);
	float fDeltaSegAngle = (2 * Math::PI / nSegments);
	unsigned short wVerticeIndex = 0 ;

	// Generate the group of rings for the sphere
	for( int ring = 0; ring <= nRings; ring++ ) {
		float r0 = r * sinf (ring * fDeltaRingAngle);
		float y0 = r * cosf (ring * fDeltaRingAngle);

		// Generate the group of segments for the current ring
		for(int seg = 0; seg <= nSegments; seg++) {
			float x0 = r0 * sinf(seg * fDeltaSegAngle);
			float z0 = r0 * cosf(seg * fDeltaSegAngle);

			// Add one vertex to the strip which makes up the sphere
			*pVertex++ = x0;
			*pVertex++ = y0;
			*pVertex++ = z0;

			Vector3 vNormal = Vector3(x0, y0, z0).normalisedCopy();
			*pVertex++ = vNormal.x;
			*pVertex++ = vNormal.y;
			*pVertex++ = vNormal.z;

			*pVertex++ = (float) seg / (float) nSegments;
			*pVertex++ = (float) ring / (float) nRings;

			if (ring != nRings) {
                               // each vertex (except the last) has six indices pointing to it
				*pIndices++ = wVerticeIndex + nSegments + 1;
				*pIndices++ = wVerticeIndex;               
				*pIndices++ = wVerticeIndex + nSegments;
				*pIndices++ = wVerticeIndex + nSegments + 1;
				*pIndices++ = wVerticeIndex + 1;
				*pIndices++ = wVerticeIndex;
				wVerticeIndex ++;
			}
		}; // end for seg
	} // end for ring

	// Unlock
	vBuf->unlock();
	iBuf->unlock();
	// Generate face list
	pSphereVertex->useSharedVertices = true;

	// the original code was missing this line:
	pSphere->_setBounds( AxisAlignedBox( Vector3(-r, -r, -r), Vector3(r, r, r) ), false );
	pSphere->_setBoundingSphereRadius(r);
        // this line makes clear the mesh is loaded (avoids memory leaks)
        pSphere->load();
 }

The parameters are

• strName - The Mesh's name. You'll use this to access it.
• r - The sphere's radius.
• nRings - Number of lines of longitude in the sphere. Defaults to 16.
• nSegments - Number of lines of latitude in the sphere. Also defaults to 16.

Example

Here's an example of how you would use this function and attach the new mesh to a SceneNode:

createSphere("mySphereMesh", 10, 64, 64);
Entity* sphereEntity = sceneMgr->createEntity("mySphereEntity", "mySphereMesh");
SceneNode* sphereNode = sceneMgr->getRootSceneNode()->createChildSceneNode();
sphereEntity->setMaterialName("material_name_goes_here");
sphereNode->attachObject(sphereEntity);

Don't forget to replace "material_name_goes_here" with the name of your material.

Creating a sphere with ManualObject

You can also create the mesh with the ManualObject class:

void createSphere(const std::string& strName, const float r, const int nRings = 16, const int nSegments = 16)
{
	ManualObject * manual = sceneMgr->createManualObject(strName);
	manual->begin("BaseWhiteNoLighting", RenderOperation::OT_TRIANGLE_LIST);
		
	float fDeltaRingAngle = (Math::PI / nRings);
	float fDeltaSegAngle = (2 * Math::PI / nSegments);
	unsigned short wVerticeIndex = 0 ;

	// Generate the group of rings for the sphere
	for( int ring = 0; ring <= nRings; ring++ ) {
		float r0 = r * sinf (ring * fDeltaRingAngle);
		float y0 = r * cosf (ring * fDeltaRingAngle);

		// Generate the group of segments for the current ring
		for(int seg = 0; seg <= nSegments; seg++) {
			float x0 = r0 * sinf(seg * fDeltaSegAngle);
			float z0 = r0 * cosf(seg * fDeltaSegAngle);

			// Add one vertex to the strip which makes up the sphere
			manual->position( x0, y0, z0);
			manual->normal(Vector3(x0, y0, z0).normalisedCopy());
			manual->textureCoord((float) seg / (float) nSegments, (float) ring / (float) nRings);

			if (ring != nRings) {
				// each vertex (except the last) has six indicies pointing to it
				manual->index(wVerticeIndex + nSegments + 1);
				manual->index(wVerticeIndex);               
				manual->index(wVerticeIndex + nSegments);
				manual->index(wVerticeIndex + nSegments + 1);
				manual->index(wVerticeIndex + 1);
				manual->index(wVerticeIndex);
				wVerticeIndex ++;
				}
		}; // end for seg
	} // end for ring
	manual->end();
	MeshPtr mesh = manual->convertToMesh(name);
	mesh->_setBounds( AxisAlignedBox( Vector3(-r, -r, -r), Vector3(r, r, r) ), false );

	mesh->_setBoundingSphereRadius(r);
       unsigned short src, dest;
   	if (!mesh->suggestTangentVectorBuildParams(VES_TANGENT, src, dest))
   	{
      	       mesh->buildTangentVectors(VES_TANGENT, src, dest);
   	}
}

You can use the above example to include it in your code.