Advanced, Experimental VFX Animation and Techniques.
Blog WK#16 (May 18), Neuronal Modelling cont'd.
The NURBS Approach
My first effort with modelling a single neuron implemented the basic extrusion technique to create dendrites and axons that converge upon and emanate from the central cell body. This extrusion technique was demonstrated in the first term. This approach however, was actually prompted by my loss of internet access during wk #5 of this term. Prior to the loss of internet access, i.e. from my one opportunity to watch the Andrew Tran maya modelling tutorial (2014), I recalled that he had used NURBS to model the dendritic and axonal projections. However, because I was unable to watch the tutorial again, I simply opted to model these projections by means of the only technique that I knew, which was extrusion. It appears I may regain internet access on Weds the 20th, but instead of waiting until then, I am reading about NURBS from Maya textbooks.
Blog WK#16 (May 18), Neuronal Modelling cont'd.
The NURBS Approach
My first effort with modelling a single neuron implemented the basic extrusion technique to create dendrites and axons that converge upon and emanate from the central cell body. This extrusion technique was demonstrated in the first term. This approach however, was actually prompted by my loss of internet access during wk #5 of this term. Prior to the loss of internet access, i.e. from my one opportunity to watch the Andrew Tran maya modelling tutorial (2014), I recalled that he had used NURBS to model the dendritic and axonal projections. However, because I was unable to watch the tutorial again, I simply opted to model these projections by means of the only technique that I knew, which was extrusion. It appears I may regain internet access on Weds the 20th, but instead of waiting until then, I am reading about NURBS from Maya textbooks.
NURBS Default Objects and Curves
From college math, it can be recalled that a spline is simply a function that defines a line segment or curve across some range of X values. Accordingly, NURBS is an acronym standing for ‘non-uniform rational B-spline’. NURBS modelling involves generating default objects, curves, and freeform surfaces. Default objects are invoked by either ‘dynamic’ or ‘keyboard’ approach. The dynamic approach involves selecting the default obj of interest (e.g. a sphere, cube, torus, plane, cone or cylinder) and then dragging in the viewport until the obj appears. The keyboard approach involves using tool settings panel to set the properties of the obj, e.g. for a sphere this includes radios and number of sections, and then simply clicking in the viewport. After generating a core default obj and perhaps combining multiple objects as necessary, the addition of curves is also frequently necessary (and this is certainly the case for my neuronal modelling). Curves are invoked by the Create drop down in the menu bar; Create > objects > Curve Tool > CV Curve Tool (Tickoo 2017).
From college math, it can be recalled that a spline is simply a function that defines a line segment or curve across some range of X values. Accordingly, NURBS is an acronym standing for ‘non-uniform rational B-spline’. NURBS modelling involves generating default objects, curves, and freeform surfaces. Default objects are invoked by either ‘dynamic’ or ‘keyboard’ approach. The dynamic approach involves selecting the default obj of interest (e.g. a sphere, cube, torus, plane, cone or cylinder) and then dragging in the viewport until the obj appears. The keyboard approach involves using tool settings panel to set the properties of the obj, e.g. for a sphere this includes radios and number of sections, and then simply clicking in the viewport. After generating a core default obj and perhaps combining multiple objects as necessary, the addition of curves is also frequently necessary (and this is certainly the case for my neuronal modelling). Curves are invoked by the Create drop down in the menu bar; Create > objects > Curve Tool > CV Curve Tool (Tickoo 2017).
NURBS Curve Fitting: Minimum Points
The Curve Tool Option Box will invoke a tool settings interface that allows one to modify the number of CV points (control vertices). A primary issue in this regard is the ‘degree’ of the curve, in other words, this algorithm is fitting a curve to a spline function, specifically a polynomial equation, with options for polynomials from the 1st to the 7th degree. For a simple 3 segment curve, i.e. a 3rd order polynomial, it is obvious that a cubic function will overlay a tighter curve than a second order function or a bezier curve. And, as below, when working with higher order polynomials, it is important to acknowledge that overlay of a curve needs to respect the need for minimum number of data points (plot points) corresponding to the function of interest (e.g. a 7th order polynomial will obviously require a minimum of 8 vertex points to assign a curve).
The Curve Tool Option Box will invoke a tool settings interface that allows one to modify the number of CV points (control vertices). A primary issue in this regard is the ‘degree’ of the curve, in other words, this algorithm is fitting a curve to a spline function, specifically a polynomial equation, with options for polynomials from the 1st to the 7th degree. For a simple 3 segment curve, i.e. a 3rd order polynomial, it is obvious that a cubic function will overlay a tighter curve than a second order function or a bezier curve. And, as below, when working with higher order polynomials, it is important to acknowledge that overlay of a curve needs to respect the need for minimum number of data points (plot points) corresponding to the function of interest (e.g. a 7th order polynomial will obviously require a minimum of 8 vertex points to assign a curve).
