# 3fill in all pixels between pairs of intersections

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Unformatted text preview: e polygon. 2.Sort the intersections in the increasing order of the x coordinate. 3.Fill in all pixels between pairs of　 intersections. Can also deal with concave polygons Span extrema Only turn on pixels whose centers are interior to the polygon: Otherwise will intrude other adjacent polygons round up values on the left edge of a span, round down on the right edge Scanline Algorithm Cons and Pros - Simple - Very serial (cannot be efficiently parallelized) - Special cases require exception handling Triangle Rasterization by Barycentric Coordinates Barycentric coordinates ● Can check whether a pixel is inside / outside the triangle ● Can interpolate the attributes at the vertices ● Often used in modern graphics cards ● Can be easily parallelized Triangle Rasterization * Barycentric Coordinates * Computing Barycentric Coordinates The triangle is composed of 3 points p0 (x0,y0), p1 (x1, y1), p2(x2,y2). For point (x,y), its barycentric coordinates can be computed by where Bounding Box of a Triangle Calculate a tight bounding box for a triangle: simply calculate pixel coordinates for each vertex, and find the minimum/maximum for each axis min (x0,x1,x2), max (x0,x1,x2) min (y0,y1,y2), max (y0,y1,y2) * Scanning inside the triangle ● For each pixel, compute the barycentric coordinates ● Color it if all the three values are in the range of [0,1] * Interpolation by Barycentric Coordinates We can use the barycentric coordinates to interpolate attributes of the triangle vertices •color, depth, normal vectors, texture coordinates c1 c2 (α,β,γ) αc1+βc2 +γc3 c3 Interpolation of Depth •When triangles are overlapped, need t...
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## This document was uploaded on 03/26/2014.

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