Texture Mapping: Motivation - Lecture Slides | CS 5501, Study notes of Computer Science

Download Texture Mapping: Motivation - Lecture Slides | CS 5501 and more Study notes Computer Science in PDF only on Docsity! 1 David Luebke 5/6/2000 CS 551 / 645: Introductory Computer Graphics Texture Mapping David Luebke 5/6/2000 Administrivia ● Assignment 4 due – No late days after this – One more assignment David Luebke 5/6/2000 Texture Mapping: Motivation ● Scenes created with diffuse lighting look convincingly three-dimensional, but are flat, chalky, and “cartoonish” ● Phong lighting lets us simulate materials like plastic and (to a lesser extent) metal, but scenes still seem very cartoonish and unreal ● Big problem: polygons are too coarse- grained to usefully model fine surface detail ● Solution: texture mapping David Luebke 5/6/2000 Texture Mapping: Motivation ● Adding surface detail helps keep CG images from looking simple and sterile ● Explicitly modeling this detail in geometry can be very expensive – Zebra stripes, wood grain, writing on a whiteboard ● Texture mapping pastes images onto the surfaces in the scene, adding realistic fine detail without exploding the geometry David Luebke 5/6/2000 Texture Mapping: Examples David Luebke 5/6/2000 Texture Mapping ● In short: it is impractical to explicitly model fine surface detail with geometry ● Solution: use images to capture the “texture” of surfaces ● Texture maps can modulate many factors that affect the rendering of a surface – Color or reflectance (diffuse, ambient, specular) – Transparency (smoke effects) – What else? 2 David Luebke 5/6/2000 Texture Mapping: Fundamentals ● A texture is typically a 2-D image – Image elements are called texels – Value stored at a texel affects surface appearance in some way ■ Example: diffuse reflectance, shininess, transparency… – The mapping of the texture to the surface determines the correspondence, i.e., how the texture lies on the surface ■ Mapping a texture to a triangle is easy (why?) ■ Mapping a texture to an arbitrary 3-D shape is more complicated (why?) David Luebke 5/6/2000 Texturing Fundamentals ● A texture is typically a 2-D array of texels ● Mapping the texture to an arbitrary 3-D shape is complex: David Luebke 5/6/2000 Texturing Fundamentals ● A texture is typically a 2-D array of texels ● Mapping the texture to an arbitrary 3-D shape is complex: David Luebke 5/6/2000 Texturing Fundamentals ● A texture is typically a 2-D array of texels ● Mapping the texture to an arbitrary 3-D shape is complex: David Luebke 5/6/2000 Texturing Fundamentals ● A texture is typically a 2-D array of texels ● Mapping the texture to an arbitrary 3-D shape is complex: http://www.cs.virginia.edu/~cs551/animations/unfold.mov David Luebke 5/6/2000 Texture Mapping: Rendering ● Rendering uses the mapping: – Find the visible surface at a pixel – Find the point on that surface corresponding to that pixel – Find the point in the texture corresponding to that point on the surface – Use the parameters associated with that point on the texture to shade the pixel