Active pixel determination for line generation in regionalized rasterizer displays

A method for selecting a pixel in a screen region on a screen of a monitor of a computer graphics display system to activate in rendering a straight line segment by a rasterizer assigned to the screen region, comprising:

• aligning a rectangular grid to pixel boundaries, wherein the screen comprises a screen space divided into at least one screen region, wherein the screen region comprises multiple pixels;
• identifying each pixel in the screen region through which the straight line segment passes, wherein a locus of the straight line segment is specified by equation A*x+B*y+C=0, wherein A, B, and C are respectively a first, second, and third constants and wherein x and y are respectively Cartesian coordinate system x-axis and y-axis values of points on the straight line segment;
• selecting each identified pixel to activate for rendering the straight line segment on the screen when the straight line segment passes through a diamond shaped area of the pixel whose boundary is defined by the lower, upper, left, and right pixel grid mid-points, wherein the pixel grid mid-points are the mid-points of the pixel boundaries and wherein the step of selecting each pixel to activate comprises:
• successively selecting once each pixel grid mid-point of the pixel grid until the pixel is marked as selected:
• evaluating expression A*x+B*y+C=0, at the pixel grid mid-point,
• storing in a memory the algebraic sign of the evaluated expression for the selected pixel grid mid-point, and
• if the algebraic sign of the evaluated expression for the selected pixel grid mid-point differs from the stored algebraic sign, marking the pixel as selected.

A program storage medium readable by a computer, embodying a software program of instructions executable by the computer to perform steps for selecting a pixel in a screen region of a screen on a monitor of a computer graphics display system to activate in rendering a straight line segment by a rasterizer assigned to the screen region, comprising:

• aligning a rectangular grid to pixel boundaries, wherein the screen comprises a screen space divided into at least one screen region, wherein the screen region comprises multiple pixels;
• identifying each pixel in the screen region through which the straight line segment passes, wherein a locus of the straight line segment is specified by equation A*x+B*y+C=0, wherein A, B, and C are respectively a first, second, and third constants and wherein x and y are respectively Cartesian coordinate system x-axis and y-axis values of points on the straight line segment;
• selecting each identified pixel to activate for rendering the straight line segment on the screen when the straight line segment passes through a diamond shaped area of the pixel whose boundary is defined by the lower, upper, left, and right pixel grid mid-points, wherein the pixel grid mid-points are the mid-points of the pixel boundaries and wherein selecting each pixel to activate comprises:
• marking the pixel as other than selected;
• setting a control variable equal to a preselected value;
• for each pixel grid mid-point of the pixel grid,
• while the pixel is marked as other than selected, multiplying the first constant by the x-axis coordinate of the pixel grid mid-point;
• multiplying the second constant by the y-axis coordinate of the pixel grid mid-point;
• adding the third constant, the result of multiplying the first constant by the x-axis coordinate of the pixel grid mid-point, and the result of multiplying the second constant by the y-axis coordinate of the pixel grid mid-point;
• and
• when the control variable is equal to the preselected value,
• storing in a memory the algebraic sign of the result of adding the third constant;
• and
• setting the control variable to a value other than the preselected value;
• otherwise, when the algebraic sign of the result of the adding the third constant differs from the stored algebraic sign,
• marking the pixel as selected.

A program storage medium readable by a computer, embodying a software program of instructions executable by the computer to perform steps for selecting a pixel in a screen region of a screen on a monitor of a computer graphics display system to activate in rendering a straight line segment by a rasterizer assigned to the screen region, comprising:

• aligning a rectangular grid to pixel boundaries, wherein the screen comprises a screen space divided into at least one screen region, wherein the screen region comprises multiple pixels;
• identifying each pixel in the screen region through which the straight line segment passes, wherein a locus of the straight line segment is specified by equation A*x+B*y+C=0, wherein A, B, and C are respectively a first, second, and third constants- and wherein x and y are respectively Cartesian coordinate system x-axis and y-axis values of points on the straight line segment;
• selecting each identified pixel to activate for rendering the straight line segment on the screen when the straight line segment passes through a diamond shaped area of the pixel whose boundary is defined by the lower, upper, left, and right pixel grid mid-points, wherein the pixel grid mid-points are the mid-points of the pixel boundaries and wherein selecting each pixel to comprises:
• successively selecting once each pixel grid mid-point of the pixel grid until the pixel is marked as selected:
• evaluating expression A*x+B*y+C at the pixel grid mid-point,
• storing in a memory the algebraic sign of the evaluated expression for the selected pixel grid mid-point, and
• if the algebraic sign of the evaluated expression for the selected pixel grid mid-point differs from the stored algebraic sign, marking the pixel as selected.