A form of "brushing" an computer graphic image is disclosed. The method includes brushing a simulated brush stroke along a path in a computer graphics image by converting the path to a series of corresponding line segments; determining a current convex brush edge of the path; determining a series of substantially equally spaced points along the convex edge; determining corresponding parametric points along the path; and utilising the parametric points to place brush template structures in the computer graphics image. In a first refinement, the opacity channel is combined such that the maximum of a current brush template opacity value and a current computer graphic image opacity channel value becomes the new current computer graphic image opacity channel value. In a second refinement, the opacity channel is combined such that the minimum of a current brush template opacity value and a current computer graphic image opacity channel value becomes the new current computer graphic image opacity channel value. In a third refinement, the computer graphic image further comprises a footprint channel which is set when each pixel is composited and the opacity channel is only composited with the computer graphic image opacity channel when the footprint channel is not set.
In a method for forming, with the aid of an electron beam (6), a polyline on a substrate (4) coated with a radiation-sensitive resist, the electron beam (6) is directed onto a surface of the substrate (4) in the direction of a Z coordinate, and the substrate (4) is displaced relative to the electron beam (6) in an X-Y plane in individual steps. After each individual step of the displacement, the electron beam (6) acts with a predefined energy input on the substrate (4) during a halt in the displacement motion. The energy input for each individual step is determined as a function of the shape of the polyline ascertained from several preceding individual steps. Also described is a corresponding apparatus with which, using electron beam lithography, it is possible to form polylines with a very uniform line width. The method and apparatus are particularly suitable for writing curved polylines.
A system that allows a user to interactively paint volumetric particles using a brush stroke. The particles are emitted from an area around the stroke path as the stroke is being made. As each stroke input event occurs, the system emits new particles from the new stroke segment and adds a segment to the particles that have already been emitted. This allows the user to interact with the particles as they are being "grown" and change a direction of a stroke thereby affecting the final image. As the particles are growing they can be affected by forces and displacements which change the position of the volumetric particle segments. The user can set or designate the stroke itself as a force which allows the user to control the flow of the generated particles.
A printer forms an approximate of a Bezier curve as a sequence of line segments. Two parametric equations, X(t) and Y(t), are employed. Two methods can be used to evaluate the parametric equations. Both use fixed point integer arithmetic to directly calculate points along the curve which are the values of the X(t) and Y(t) equations. The first method sets the number of steps of the parametric variable are equal to an integral power of 2. This gives a predictable execution time and uses line segments to connect the points as a piecewise straight line approximation to the curve. The number of steps is set as the next higher power of 2 than an estimated length of the curve. The second method allows Y(t), the scan line variable, to change only in predetermined integer steps. The value of X(t) is evaluated for each t corresponding to the integer step in Y(t). This second method has a natural advantage, if a closed path is being decomposed as a run array rather than a collection of trapezoids. Both methods create the lines segments in natural scan line order. This is advantageous for polygon fill algorithms because it eliminates the need for edge sorting.
