its center lies exactly on the triangle edge (or multiple edges in case of corners) that is (or, in case of corners, all are) either top or left edge.Ī top edge is an edge that is exactly horizontal and lies above other edges, and a left edge is a non-horizontal edge that is on the left side of the triangle.its center lies completely inside the triangle.One set of such rules is called a top-left rule, which states that a pixel is rasterized if and only if This leads to establishing rasterization rules to guarantee the above conditions.
Overdrawing pixels can also mean wasting computing power on pixels that would be overwritten. This is to guarantee that the result doesn't depend on the order in which the triangles are rasterized. no pixel is rasterized more than once, i.e.leaves no holes (non-rasterized pixels) between the triangles, so that the rasterized area is completely filled (just as the surface of adjacent triangles).
Properties that are usually required from triangle rasterization algorithms are that rasterizing two adjacent triangles (i.e.
Before rasterization, individual polygons are broken down into triangles, therefore a typical problem to solve in 3D rasterization is rasterization of a triangle. Rasterizing triangles using the top-left ruleĪ common representation of digital 3D models is polygonal. This is because there is no motivation for modifying the techniques for rasterization used at render time and a special-purpose system allows for high efficiency. The process of rasterizing 3D models onto a 2D plane for display on a computer screen (" screen space") is often carried out by fixed function (non-programmable) hardware within the graphics pipeline. Shading may take into account physical effects such as light position, their approximations or purely artistic intent. The specific color of each pixel is assigned by a pixel shader (which in modern GPUs is completely programmable). However, rasterization is simply the process of computing the mapping from scene geometry to pixels and does not prescribe a particular way to compute the color of those pixels. Compared with other rendering techniques such as ray tracing, rasterization is extremely fast and therefore used in most realtime 3D engines. Rasterization is one of the typical techniques of rendering 3D models. Bresenham's line algorithm is an example of algorithm used to render a line.Īlgorithms such as Midpoint circle algorithm are used to render circle onto a pixelated canvas.
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