Day09 - Texture Mapping Applications Bump Mapping a family...

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Texture Mapping Applications
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Bump Mapping a family of techniques for representing small-scale detail better than ordinary texture mapping but usually less realistic than actual geometry implemented in the fragment shader idea: adjust shading parameters so that the viewer sees fine surface detail without actually changing the base geometry use texture values to change the normal vector
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Bump Mapping bump map encodes the change in the normal vector direction in which coordinate system? world (or eye) rotate the object and the surface appearance changes object works for rigid transformations hard to reuse between different objects
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Bump Mapping modern bump mapping is usually done in surface- local coordinate space each point has coordinates (0, 0, 0) the unperturbed normal vector at the point has coordinates (0, 0, 1) the tangent vector at the point has coordinates (1, 0, 0) the bitangent vector at the point has coordinates (0, 1, 0) need to store (or calculate) the tangent vector at each point
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Bump Mapping
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Bump Mapping one kind of bump mapping perturbs the normal vector in the tangent and bitangent directions one channel of the texture encodes the perturbation magnitude in the tangent direction one channel of the texture encodes the perturbation magnitude in the bitangent direction
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Bump Mapping 0______128______255 no perturbation 0______128______255 +’ve perturbation 0______128______255 -’ve perturbation
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Bump Mapping if the normal vector perturbation is defined in surface-local coordinates then we have to either: transform light and view direction vectors into surface- local coordinates, or transform the perturbed normal vector into whatever coordinate system the lighting is being performed
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Bump Mapping tangent vector in eye coordinates bitangent vector in eye coordinates normal vector in eye coordinates the rotation matrix transforms vectors (but not points!) in surface-local coordinates to eye coordinates eye t eye b eye n = | | | | | | eye eye eye eye surf n b t R
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This note was uploaded on 02/13/2012 for the course CSE 4431 taught by Professor Burton during the Winter '12 term at York University.

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Day09 - Texture Mapping Applications Bump Mapping a family...

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