Class9

# Class9 - Class 9 Procedural Textures and Environment Maps...

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Class 9. Procedural Textures and Environment Maps HW5 Ulrich Neumann CS580 (Computer Graphics Rendering)

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Texture can set any parameters Textures can be used to modify or set any parameters of the rendering process Geometry, surface characteristics, lighting and shading model, Displacement, normal perturbation, shadow maps, reflection, etc. .. (survey of textures - Heckbert, and any books)
Texture I/O Texture output parameters can be 1D, 2D, 3D, . .. any-D Texture input parameters can be 2D (u,v), or 3D (u,v,w) for surface or volume mappings Input/Output parameters can also include surface orientation vectors Tangent (t) , normal (n) , binormal (s) (usually specified in model space) (u,v, t,n,s) can be used to orient a bumpmap texture on a surface Normal perturbation is f(u,v) = (dn/dt, dn/ds) A 2D parameter (uv) maps to a 2D modification of a 3D vector at each pixel – bump mapping

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Bump Mapping Use texture to perturb normals - create a bump-like effect + = original surface bump map modified surface NOTE : Does not alter the actual geometry Bump map only affects the shading process … so there is inconsistency at silhouette edges
Bump Map Examples

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Textures are general mapping functions Lookup table images are only one evaluation method Mathematical or procedural functions are another.
Fractal texture(1) A fractal texture function is evaluated as an iterative function in the plane This is perfect for a texture since we have 2D texture coords A Mandlebrot set X = X 2 + C where X and C are complex numbers X = (Xr + Xi) i=sqrt(-1) C = texture coords u+vi, X = 0+0i initially Complex multiply XY = (Xr Yr - XiYi) r + (Xr Yi + XiYr) i

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Fractal texture(2) The Julia set is also X = X 2 + C – X = u+vi C = constant C = (-0.12375+0.56805i) or (-0.012+0.74i) : possible start values For either function, do N-iterations and evaluate the result X – N = 100 – 500 (for example – higher N means more detail) – Length (X) = sqrt(Xr 2 + |Xi| 2 ) measured after iterations
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## This note was uploaded on 04/22/2010 for the course CS 580 at USC.

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Class9 - Class 9 Procedural Textures and Environment Maps...

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