adding surface detail

Graphics

Graphics Lab @ Korea University Graphics Lab @ Korea University

http://kucg.korea.ac.kr

Adding Surface DetailAdding Surface Detail

고려대학교 컴퓨터 그래픽스 연구실

KUCG



3D Rendering Pipeline

Model TransformationModel Transformation

LightingLighting

Viewing TransformationViewing Transformation

Projection TransformationProjection Transformation

ClippingClipping

Viewport TransformationViewport Transformation

Scan ConversionScan Conversion

3D Primitives

Image

3D Modeling Coordinates

3D World Coordinates

3D World Coordinates

3D Viewing Coordinates

2D Projection Coordinates

2D Projection Coordinates

2D Device Coordinates

2D Device Coordinates

Surface detailsSurface detailscan be added...can be added...

KUCG



Overview

Texture mapping methods Mapping Filtering

Texture mapping applications Modulation texture Bump mapping Environment mapping

KUCG



Texture Surface

Add visual detail to surfaces of 3D objects

Polygonal ModelPolygonal Model

With Surface TextureWith Surface Texture

KUCG



Texture Mapping

2D projective transformation Texture coordinate system (ss, tt) to Device coordinate system (xx, yy)

KUCG



Textures

Color variation in interior of 3D polygon When scan converting a polygon

Vary pixel colors according to values fetched from a texture

tt

ss

Texture SpaceTexture Space

yy

zz

xx

Object SpaceObject Space

yyss

xxss

Image SpaceImage Space

Viewing and ProjectionViewing and ProjectionTransformationTransformation

Texture-SurfaceTexture-SurfaceTransformationTransformation

KUCG



Texture Mapping

Steps: Define texture Specify mapping from texture to surface Lookup texture values during scan conversion

TextureTextureCoordinateCoordinate

SystemSystem

ModelingModelingCoordinateCoordinate

SystemSystem

DeviceDeviceCoordinateCoordinate

SystemSystem

tt

ssvvuu

(0, 1)(0, 1)

(0, 0)(0, 0)

(1, 0)(1, 0)

yyxx

KUCG



Texture Mapping

Scan conversion Interpolate texture coordinates Distortion due to the bilinear interpolation

Subdivide the polygon into smaller ones

αα ββ

(u(u11, v, v11))

(u(u33, v, v33))(u(u22, v, v22))

KUCG



Texture Mapping

Linear InterpolationLinear Interpolationof Texture Coordinateof Texture Coordinate Corrected InterpolationCorrected Interpolation

KUCG



Texture Sampling

To determine color at each pixel in image

tt

ss

yy

zz

xx

yyss

xxss

KUCG



Texture Filtering

To avoid aliasing problem

Point SamplingPoint Sampling Corrected ResultCorrected Result

KUCG



Texture Filtering

Ideally, use elliptically shaped convolution filters In practice, use rectangles

Texture SpaceTexture Space Screen SpaceScreen Space

KUCG



Mip Maps

Keep textures prefiltered at multiple resolutions For each pixel

Linearly interpolate between two closest levels Trilinear filtering

Fast and easy for hardware

KUCG



Overview


Texture mapping applications Modulation texture Bump mapping Environment mapping

KUCG



Modulation Texture

))RV((, TTRSL LLn

SDAAE IKIKISKLNKIKIstTI ))RV((, TTRSL LLn

SDAAE IKIKISKLNKIKIstTI Texture Value

TextureTexture

Shaded ColorShaded Color

KUCG



Bump Mapping

Perturbate surface normals

KUCG



Bump Mapping

KUCG



Environment Mapping

Map texture values to the environment map

Surface

ProjectionReference Point

Pixel Area

Pixel Projectiononto Environment

Map

KUCG



Summary


Texture mapping applications Modulation textures Bump mapping Environment mapping

KUCG



Wireframe

KUCG



Ambient Illumination Only

KUCG



Flat Shaded Polygonswith Diffuse Reflection

KUCG



Gouraud Shaded Polygonswith Diffuse Reflection

KUCG



Gouraud Shaded Polygonswith Specular Reflection

KUCG



Phong Shaded Polygonswith Specular Reflection

KUCG



Curved Surfaceswith Specular Reflection

KUCG



Improved Illumination Modelwith Multiple Lights

KUCG



Texture Mapping

KUCG



Bump Mapping

KUCG



Reflection Mapping

adding surface detail

Documents