Texturing - hallym.ac.krgraphics.hallym.ac.kr/teach/2005/gp1/src/08texture.pdf · 2008-09-10 · To learn how to specify the part of a texture that gets mapped to the triangle

Game Programming

Sun-Jeong Kim http://www.hallym.ac.kr/~sunkim/teach/2005/gp1

Texturing

May 02, 2005


Texturing


Objectives

To learn how to specify the part of a texturehow to specify the part of a texture

that gets mapped to the triangle

To find out how to create textureshow to create textures

To learn how textures can be filteredhow textures can be filtered to create

a smoother image


Texture Mapping

Technique that allows us to map image data onto a triangle

to increase the details and realism of our scene

TextureTexturea matrix pixels similar to a surface but can be mapped to triangles

TextureTexture

MappingMapping


Texture Coordinates (1)

Texture coordinate systemconsist of a u-axis and v-axis

TexelTexela pair of u, v coordinates to identify an element on the texture (0, 0) (1, 0)

(0, 1) (1, 1)

+U

+V

normalizednormalizedcoordinatecoordinate

intervalinterval[0, 1][0, 1]



Define a corresponding triangle on the texture that is to be mapped to the 3D triangle

(0, 0) (1, 0)

(0, 1) (1, 1)

+U

+V

(x1, y1, z1) (x2, y2, z2)

(x3, y3, z3)

(u2, v2)

(u3, v3)

(u1, v1)

3D Triangle Corresponding Texture Triangle

TextureTexture

MappingMapping



Modify a vertex structure

texture isn’t mapping until the rasterization stage where the 3D triangle has been transformed to screen space

struct Vertex{

float x, y, z;float nx, ny, nz;float u, v;float u, v;

static const DWORD FVF;};const DWORD Vertex::FVF = D3DFVF_XYZ|D3DFVF_NORMAL|D3DFVF_TEXD3DFVF_TEX;


Creating and Enabling a Texture (1)

Load texture data into IDirect3DTexture9object

read from an image file: BMP, DDS, DIB, JPG, PNG, and TGA

ex)

HRESULT D3DXCreateTextureFromFile( LPDIRECT3DDEVICE9 pDevice,LPCSTR pSrcFile,LPDIRECT3DTEXTURE9* ppTexture

);

IDirect3DTexture9* _stonewall;D3DXCreateTextureFromFileD3DXCreateTextureFromFile( _device, “stonwall.bmp”,

&_stonwall );


Creating and Enabling a Texture (2)

Set the current texture

cf) multitexturing – eight textures can be set up

ex)

Disable a texture at a particular texturing stage

Use different textures

HRESULT IDirect3DDevice9::SetTexture( DWORD Stage,IDriect3DBaseTexture9* pTexture

);

_device->SetTextureSetTexture( 0, _stonwall );

_device->SetTexture( 0, 00 );renderObjectWithoutTexture( );

_device->SetTexture( 0, tex0tex0 );drawTriangleTex0( );_device->SetTexture( 0, tex1tex1 );drawTriangleTex1( );


Texture Mapping Steps (1)

Define a texture

Specify mapping from a texture to a surface

Look up texture values during rasterization

v

u

ys

xs

(0, 0, 0)

(1, 0, 0)

(1, 1, 0)

(0, 1, 0)

2DTexture

CoordinateSystem

3DModeling

CoordinateSystem

(Local Space)

2DDevice

CoordinateSystem

(Screen or Viewport Space)

y

xz



Rasterizationdevice modeling texture coordinate systems

2D projective transformation (texture device)

v

u

ys

xs

2DTexture

CoordinateSystem

3DModeling

CoordinateSystem

2DDevice

CoordinateSystem

y

xz



Interpolate texture coordinates

Problem distortion!!!due to bilinear interpolation

cut polygons into smaller ones

perspectively divide at each pixel

α βγ

(u1, v1)

(u2, v2)(u3, v3)


Distortion vs. Perspective Division

Linear Interpolationof Texture Coordinates

Corrected Interpolationwith Perspective Division


Texture Filtering (1)

Sample texture to determine color at each pixel in image (or screen)

v

u

ys

xs

y

xz


Texture Filtering (2)

Problem aliasing!!!

Point Sampling Area Filtering


Filters (1)

Texture triangle is not the same size as the screen triangle

magnificationmagnification – texture triangle < screen triangle

minificationminification – texture triangle > screen triangle

v

u xs

ys

TexelPixel

Magnification

v

u

Texel

xs

ys

Pixel

Minification


Filters (2)

FilteringFilteringtechnique to help smooth out the distortions which will occur in magnification or minification

Direct3D provides three different types of filters:nearest point sampling

linear filtering

aniotropic filtering

determine the quality of the anisotropic filtering

FastFast_device->SetSampleState(0, D3DSAMP_MAGFILTER, D3DTEXF_POINTD3DTEXF_POINT);_device->SetSampleState(0, D3DSAMP_MINFILTER, D3DTEXF_POINTD3DTEXF_POINT);

_device->SetSampleState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEARD3DTEXF_LINEAR);_device->SetSampleState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEARD3DTEXF_LINEAR);

_device->SetSampleState(0, D3DSAMP_MAGFILTER, D3DTEXF_ANISOTROPICD3DTEXF_ANISOTROPIC);_device->SetSampleState(0, D3DSAMP_MINFILTER, D3DTEXF_ANISOTROPIC);

HighHighQualityQuality

_device->SetSampleState(0, D3DSAMP_MAXANISOTROPIYD3DSAMP_MAXANISOTROPIY, 4);


Mipmaps (1)

A chain of mipmapsmipmaps for a texturepre-filtering images

take a texture and create a series of smaller lower resolution textures but customize the filtering

Each successive mipmap is half the size of the prevous mipmap

256x256 128x128 64x64 32x32 16x16


Mipmaps (2)

Mipmap filter

Filter – D3DTEXF_NONE

D3DTEXF_POINT

D3DTEXF_LINEAR

256x256 128x128 64x64 32x32 16x16

_device->SetSampleState(0, D3DSAMP_MIPFILTERD3DSAMP_MIPFILTER, Filter);


Mipmap (3)

Using mipmaps with Direct3DD3DXCreateTextureFromFile will generate a

mipmap chain if the device supports mipmaps

Direct3D automatically selects the mipmap that matches the screen triangle the best


Address Modes

Behavior for texture coordinates that go outsize the [0, 1] range

four types – wrap, border color, clamp, mirror

Wrap Border Color Clamp Mirror


Sample: Textured Quad


Tasks Required for Adding Textures

Construct the vertices of the objects with the texture coordinates specifiedLoad a texture into an IDirect3DTexture9interface using the D3DXCreateTextureFromFile function

Set the minification, magnification, and mipmapfilters

Before you draw an object, set the texture that is associated with the object with IDirect3DDevice9::SetTexture


Global Variables


Constructing a Quad


Loading a Texture


Rendering a Quad


Sample: Address Modes


Specifying Texture Coordinates


Setting Address Modes


Result – CLAMP


Result – Mirror


Sample: Textured Cube


Vertex Structure


Cube Class


Constructor (1)


Constructor (2)


Constructor (3)


Destructor & draw( )


Setup( ) (1)


Setup( ) (2)


Display( ) (1)


Display( ) (2)


Display( ) (2-1)

Error!!Error!!'draw' : cannot convert parameter 2 from 'const struct _D3DMATERIAL9 *' to 'struct _D3DMATERIAL9 *'


Display( ) (2-2)

Documents

Texturing - hallym.ac.krgraphics.hallym.ac.kr/teach/2005/gp1/src/08texture.pdf · 2008-09-10 · To learn how to specify the part of a texture that gets mapped to the triangle