gistfile1.txt

-(void) draw:(CCRenderer *)renderer transform:(const GLKMatrix4 *)transform
{
	// Drawing the triangle fan. Simple explanation of how a triangle fan is drawn:
	// http://stackoverflow.com/questions/8043923/gl-triangle-fan-explanation
	
	// in a triangle fan the first 3 vertices form one triangle, then each additional vertex forms another triangle
	// thus number of triangles is number of vertices minus the initial 2 vertices for the first triangle
	int numTriangles = _numVertices - 2;
	CCRenderBuffer buffer = [renderer enqueueTriangles:numTriangles
										   andVertexes:_numVertices
											 withState:self.renderState
									   globalSortOrder:0];
	
	// update the vertex coordinates using each child node's current position, and add them to the render buffer
	int i = 0;
	CGPoint centerPos = ((CCNode*)_children[0]).position;
	
	for (CCNode* child in _children)
	{
		CGPoint vertexPos = child.position;
		if (i > 0)
		{
			// elongate vertex position outwards by the body size
			CGPoint vectorToCenter = ccpSub(child.position, centerPos);
			CGFloat length = ccpLength(vectorToCenter);
			CGPoint normalVector = ccpMult(vectorToCenter, 1.0 / length);
			vectorToCenter = ccpMult(normalVector, length + _enlargeDrawRadius);
			vertexPos = ccpAdd(vectorToCenter, centerPos);
		}
		
		_vertices[i].position = GLKVector4Make(vertexPos.x, vertexPos.y, 0.0, 1.0);
		
		CCRenderBufferSetVertex(buffer, i, CCVertexApplyTransform(_vertices[i], transform));
		i++;
	}
	
	// adding the first circumference vertex as the last vertex closes the (circular) polygon
	int lastIndex = _numVertices - 1;
	_vertices[lastIndex].position = GLKVector4Make(_vertices[1].position.x, _vertices[1].position.y, 0.0, 1.0);
	CCRenderBufferSetVertex(buffer, lastIndex, CCVertexApplyTransform(_vertices[lastIndex], transform));
	
	for (int i = 0; i < numTriangles; i++)
	{
		// draw triangle from center (0) to circumference vertices (i+1, i+2), re-using each circumference vertex twice
		CCRenderBufferSetTriangle(buffer, i, 0, i+1, i+2);
	}
}

above code draws a sprite by using the physicsbody child nodes as initial vertices and texture coordinates
(ie draws a soft-body physics sprite)