Paint Strokes |
The shape of the
paint strokes was defined within the tiled texture map used within my shader and created
using Painter. To do
this I used Painters 'loaded oil brush' to create the desired look. The advantage
of this approach was that if the user wished to change the style of paint strokes being
applied they could simply change the shape of the strokes within the texture. Vincent Vangogh used thick daubs of oil paint, applied in a variety of patterns (depending on the painting). The paint daubs clearly showed the grooves left by the brush bristles. The painting below is a good example of his painting style as it shows how, where possible, he applied brush strokes to conform to the contours of the objects being painted. There is little random application of paint. Even in the swirling patterns of the sky it is obvious that he has attempted to follow it's form (emphasising the stars and moon).
The Starry Night (1889): Notice how the paint strokes follow the contours of the objects.
I mimicked this characteristic by applying textures to NURBS surfaces as ST projections. Rather than attempting to wrap the textures around an object in an artificial fashion (such as a spherical projection), ST projection meant that textures were mapped according to the surface paramatization of the underlying NURBS surface. In other words the textures followed the contours of the surface and were spaced according to the position of the isoparms on the NURBS object. By moving isoparms on a surface and by squashing and stretching groups of control vertices, I could control the mapping of the brush strokes.
ST Texture Mapping: Notice how the texture follows the object surface
The orientation and placement of the strokes was controlled using Maya texture placement nodes (referenced in my Renderman shader). The ability to do this was very useful, as it meant I could visualise the placement of the textures within Maya in realtime and then be confident of how they would render in PRman. |