COMPUTER GRAPHICS CS 482 FALL 2014 OCTOBER 6, 2014 TEXTURE
MAPPING TEXTURES BUMP MAPPING ENVIRONMENT MAPPING PROCEDURAL
TEXTURING
Slide 3
TEXTURES CS 482 FALL 2014 BASICS OCTOBER 6, 2014: TEXTURE
MAPPINGPAGE 149 MAPPING A PATTERN ONTO THE OBJECTS SURFACES CAN
GREATLY ENHANCE THE SCENES APPEAL AND/OR REALISM.
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TEXTURES CS 482 FALL 2014 UV COORDINATES OCTOBER 6, 2014:
TEXTURE MAPPINGPAGE 150 ONE APPROACH TO TEXTURE MAPPING DIRECTLY
MAPS THE 2D TEXTURE COORDINATES (CALLED UV SPACE) INTO THE 3D WORLD
SPACE COORDINATES. CYLINDRICAL MAPPING SPHERICAL MAPPING PLANAR
MAPPING
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TEXTURES CS 482 FALL 2014 TILING OCTOBER 6, 2014: TEXTURE
MAPPINGPAGE 151 WHEN THE SURFACE BEING TEXTURED IS MUCH LARGER THAN
THE IMAGE BEING MAPPED, IT IS POSSIBLE TO TILE THE IMAGE REPEATEDLY
OVER THE SURFACE. CARE MUST BE TAKEN TO DEVELOP IMAGES THAT DO NOT
PRODUCE DISCERNIBLE SEAMS OR PATTERNS WHEN TILED. THE SEAMS AND
PATTERNS ARE MORE NOTICEABLE IN THE TILED HEDGE IMAGE ON THE LEFT
THAN THE ONE ON THE RIGHT.
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BUMP MAPPING CS 482 FALL 2014 ADJUSTING NORMAL VECTORS OCTOBER
6, 2014: TEXTURE MAPPINGPAGE 152 TO ADD MORE REALISM TO A
TEXTURE-MAPPED IMAGE, AN ADDITIONAL ACTION, KNOWN AS A BUMP
MAPPING, CAN BE APPLIED TO THE OBJECTS SURFACE. APPLYING THE
TEXTURE TO THIS SURFACE, WHILE COMPUTATIONALLY EXPENSIVE, PRODUCES
A SENSE OF DEPTH FAR SUPERIOR TO SIMPLE TEXTURE MAPPING. BUMP
MAPPING (LEFT) ALTERS THE SURFACES NORMAL VECTOR, WHILE
DISPLACEMENT MAPPING (RIGHT) ALTERS THE SURFACE ITSELF.
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BUMP MAPPING CS 482 FALL 2014 INTACT SILHOUETTE OCTOBER 6,
2014: TEXTURE MAPPINGPAGE 153 BUMP MAPPING BASICALLY APPLIES A
PATTERN OF PERTURBATIONS TO THE NORMAL VECTORS ON THE SURFACE OF
THE OBJECT BEING RENDERED. = WHEN AN ILLUMINATION MODEL (E.G.,
PHONG SHADING) IS APPLIED WITH THESE ALTERED NORMAL VECTORS, THE
APPEARANCE OF A RICH, DETAILED TEXTURE RESULTS.
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BUMP MAPPING CS 482 FALL 2014 DISPLACEMENT MAPPING OCTOBER 6,
2014: TEXTURE MAPPINGPAGE 154 DISPLACEMENT MAPPING, WHICH ACTUALLY
ALTERS THE OBJECTS UNDERLYING GRID TO IMPLEMENT THE 3D SURFACE
DETAILS, ELIMINATING THE SILHOUETTE INCONSISTENCIES, BUT GREATLY
INCREASING THE PROCESSING COST.
Slide 9
ENVIRONMENT MAPPING CS 482 FALL 2014 SPHERICAL MAPPING OCTOBER
6, 2014: TEXTURE MAPPINGPAGE 155 TO PRODUCE AN EFFECT THAT APPEARS
LIKE 3D REFLECTION, ENVIRONMENT MAPPING PROJECTS THE SURROUNDING
ENVIRONMENT ONTO A 2D IMAGE AND THEN TEXTURE MAPS THAT RESULT ONTO
THE REFLECTIVE OBJECT. CROSS-SECTION OF ENVIRONMENT, WITH FRONT ON
THE RIGHT AND REAR ON THE LEFT WITH SPHERICAL MAPPING, THE ENTIRE
ENVIRONMENT IS MAPPED TO A RADIUS- ONE DISK (THE FRONT TO THE INNER
CORE OF THE DISK AND THE REAR TO THE OUTER RING). BAD NEWS: THE
ENTIRE PERIMETER OF THE SPHERE MAP IS MAPPED TO A SINGULARITY ON
THE FAR SIDE OF THE OBJECT.
Slide 10
ENVIRONMENT MAPPING CS 482 FALL 2014 LATITUDE MAPPING OCTOBER
6, 2014: TEXTURE MAPPINGPAGE 156 WITH LATITUDE MAPPING, THE SPHERE
IS TREATED LIKE A GLOBE AND MAPPED FROM 3D TO 2D VIA LONGITUDES AND
LATITUDES. BAD NEWS: THERE IS STILL A SEAM WHERE THE LEFT AND RIGHT
EDGES OF THE TEXTURE MAP MEET WHEN MAPPED TO THE OBJECT.
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ENVIRONMENT MAPPING CS 482 FALL 2014 CUBE MAPPING OCTOBER 6,
2014: TEXTURE MAPPINGPAGE 157 IN CUBE MAPPING, SIX TEXTURES ARE
CREATED FROM EACH POSITIVE AND NEGATIVE CARTESIAN DIRECTION
SURROUNDING THE OBJECT. BAD NEWS: PARTICULAR FACETS OF THE OBJECT
MIGHT REQUIRE UP TO THREE RENDERINGS (E.G., FRONT, RIGHT, AND
BOTTOM) TO ENSURE THAT ALL FACES HIT BY THE REFLECTION RAYS ARE
DISPLAYED.
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PROCEDURAL TEXTURING CS 482 FALL 2014 PERLIN NOISE OCTOBER 6,
2014: TEXTURE MAPPINGPAGE 158 CERTAIN TEXTURES IN NATURE (CLOUDS,
MARBLE, STREAMS, ETC.) TEND TO FOLLOW A PSEUDORANDOM PATTERN THAT
MAY BE SIMULATED BY MEANS OF NOISE FUNCTIONS. A SET OF PSEUDORANDOM
VALUES ARE GENERATED AT SET INTERVALS. A CONTINUOUS CURVE IS
GENERATED BY SMOOTHLY INTERPOLATING BETWEEN THESE VALUES. SEVERAL
CURVES LIKE THIS ARE GENERATED, EACH WITH CERTAIN RESTRICTIONS ON
THE AMPLITUDE (THE DIFFERENCE BETWEEN THE MINIMUM AND MAXIMUM
VALUES GENERATED) AND THE WAVELENGTH (THE INTERVAL GAP). SUMMING
THESE CURVES YIELDS THE FINAL NOISE FUNCTION.
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PROCEDURAL TEXTURING CS 482 FALL 2014 NOISE TEXTURES OCTOBER 6,
2014: TEXTURE MAPPINGPAGE 159 EXTENDING THE GENERATING OF A NOISE
FUNCTION TO TWO DIMENSIONS YIELDS INTERESTING AND USEFUL TEXTURES.
+++++=
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PROCEDURAL TEXTURING CS 482 FALL 2014 TEXTURE SYNTHESIS OCTOBER
6, 2014: TEXTURE MAPPINGPAGE 160 TO SYNTHESIZE A LARGER IMAGE THAT
FOLLOWS THE SAME PATTERN AS A GIVEN SMALLER IMAGE, START WITH A
NOISY IMAGE OF THE DESIRED SIZE. REPLACE EACH PIXEL IN THE NEW
IMAGE BY LOOKING AT ITS ALREADY COLORED NEIGHBORS, FINDING A PIXEL
IN THE ORIGINAL IMAGE WITH THE CLOSEST PATTERN OF NEIGHBORS, AND
COLORING THE NEW PIXEL WITH THAT OLD PIXELS COLOR.