Into n regions of equal size and randomly sample

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Unformatted text preview: are more sensitive to aliases than noise Stochastic Sampling ● One approach to solve this is to randomly sample over the pixels ● Jittering : subdivide into n regions of equal size and randomly sample inside each region ● Compute the colour at the sample and average ● Can precompute a table and recycle it or simply jitter on the fly Comparison Accumulation Buffer (A-Buffer) • Use a buffer that has the same resolution as the original image • To obtain a 2x2 sampling of a scene, 4 images are made by shifting the frame buffer horizontally/vertically for half a pixel • The results are accumulated and the final results are obtained by averaging • We can recycle the vertex attributes Pixel center Subsampled point Today • Texture mapping • Antialiasing • Antialiasing textures Aliasing of textures Happens when the camera is zoomed too much into the textured surface (magnification) Several texels (pixels of the texture) covering a pixel’s cell (minification) Texture Magnification • Zooming too much into a surface with a texture • One texel covering many pixels Bilinear Interpolation • Mapping the pixel centre to the uv coordinates • Computing the pixel colour by interpolating the surrounding texel values Bilinear Interpolation - 2 • For (pu, pv), compute its (u,v) coordinates by barycentric coordinates • u = pu – (int)pu, v = pv - (int)pv • xl = pu, xr = pu +1, yb = pv, yt = pv +1, – (pu, pv) : the pixel centre mapped into the texture space – b(pu,pv) : the colour at point pu, pv – t(x,y) : the texel colour at (x,y) – u = pu – (int)pu, v = pv - (int)pv Texture Minification Many texels covering a pixel’s cell • Results in...
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This document was uploaded on 03/26/2014.

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