Texture MappingTexture Mapping Ltjg Omer ArisutLtjg Omer Arisut

Turkish NavyTurkish Navy

Texture MappingTexture Mapping Ltjg Omer ArisutLtjg Omer Arisut

Turkish NavyTurkish Navy

Texture Mapping

-A texture is a rectangular pixel map -A texture is a rectangular pixel map that is mapped onto some surfacethat is mapped onto some surface

-Texture mapping is the process of -Texture mapping is the process of mapping a scanned or hand-drawn mapping a scanned or hand-drawn image (called the texture map or image (called the texture map or simply the texture) onto a polygon.simply the texture) onto a polygon.

-A texture is a rectangular pixel map -A texture is a rectangular pixel map that is mapped onto some surfacethat is mapped onto some surface

-Texture mapping is the process of -Texture mapping is the process of mapping a scanned or hand-drawn mapping a scanned or hand-drawn image (called the texture map or image (called the texture map or simply the texture) onto a polygon.simply the texture) onto a polygon.

Texture Mapping Methods

-2D texture mapping -2D texture mapping

•Color, bump, displacement, transparency Color, bump, displacement, transparency mapping, etc. mapping, etc.

•3D texture mapping 3D texture mapping

•Reflection and solid texture mapping Reflection and solid texture mapping

-2D texture mapping -2D texture mapping

•Color, bump, displacement, transparency Color, bump, displacement, transparency mapping, etc. mapping, etc.

•3D texture mapping 3D texture mapping

•Reflection and solid texture mapping Reflection and solid texture mapping

2D texture mapping

--A ‘cheap’ way of enhancing the the surface definition A ‘cheap’ way of enhancing the the surface definition

In real life, many surfaces are multi-colored In real life, many surfaces are multi-colored

•2D texture mapping involves applying a 2D image to the surface of 2D texture mapping involves applying a 2D image to the surface of a 3D object a 3D object

•Textures may be ‘real’, manually generated or procedurally Textures may be ‘real’, manually generated or procedurally generated generated

•The process of applying the texture is the ‘mapping’ The process of applying the texture is the ‘mapping’

•The two mapping processes: The two mapping processes:

•Projecting the image onto the surface Projecting the image onto the surface

•Stretching the image to fit on the surface Stretching the image to fit on the surface

--A ‘cheap’ way of enhancing the the surface definition A ‘cheap’ way of enhancing the the surface definition

In real life, many surfaces are multi-colored In real life, many surfaces are multi-colored

•2D texture mapping involves applying a 2D image to the surface of 2D texture mapping involves applying a 2D image to the surface of a 3D object a 3D object

•Textures may be ‘real’, manually generated or procedurally Textures may be ‘real’, manually generated or procedurally generated generated

•The process of applying the texture is the ‘mapping’ The process of applying the texture is the ‘mapping’

•The two mapping processes: The two mapping processes:

•Projecting the image onto the surface Projecting the image onto the surface

•Stretching the image to fit on the surface Stretching the image to fit on the surface

Basic Idea

Take a source polygon defined within a Take a source polygon defined within a texture map and project it onto a texture map and project it onto a destination polygondestination polygon

The texture map is most often defined in The texture map is most often defined in rectangular (u,v) coordinates called rectangular (u,v) coordinates called texels. texels.

Take a source polygon defined within a Take a source polygon defined within a texture map and project it onto a texture map and project it onto a destination polygondestination polygon

The texture map is most often defined in The texture map is most often defined in rectangular (u,v) coordinates called rectangular (u,v) coordinates called texels. texels.

Operations in Texture Mapping

- Determining which texture pixel (texel) - Determining which texture pixel (texel) should be used for the mapping on to the should be used for the mapping on to the target fragment (done during scan conversion)target fragment (done during scan conversion)

-- Filtering the texel color value (with or Filtering the texel color value (with or without mipmapping)—Pixel Operationwithout mipmapping)—Pixel Operation

-- Blending the texel with the fragment -- Blending the texel with the fragment -- Pixel OperationPixel Operation

- Determining which texture pixel (texel) - Determining which texture pixel (texel) should be used for the mapping on to the should be used for the mapping on to the target fragment (done during scan conversion)target fragment (done during scan conversion)

-- Filtering the texel color value (with or Filtering the texel color value (with or without mipmapping)—Pixel Operationwithout mipmapping)—Pixel Operation

-- Blending the texel with the fragment -- Blending the texel with the fragment -- Pixel OperationPixel Operation

Projection mapping

--In projection mapping the image is projected through In projection mapping the image is projected through

space space

•Wherever it ‘hits’ the surface the surface becomes the Wherever it ‘hits’ the surface the surface becomes the color of the texture color of the texture

•Cylindrical projection, Rectangular Cylindrical Cylindrical projection, Rectangular Cylindrical projection, Spherical projection, and Planar projection projection, Spherical projection, and Planar projection are projection mapping methods.are projection mapping methods.

--In projection mapping the image is projected through In projection mapping the image is projected through

space space

•Wherever it ‘hits’ the surface the surface becomes the Wherever it ‘hits’ the surface the surface becomes the color of the texture color of the texture

•Cylindrical projection, Rectangular Cylindrical Cylindrical projection, Rectangular Cylindrical projection, Spherical projection, and Planar projection projection, Spherical projection, and Planar projection are projection mapping methods.are projection mapping methods.

Cylindrical Mapping

Applying a texture map to a cylinder is easy if we use Applying a texture map to a cylinder is easy if we use cylindrical coordinates. The texture just wraps cylindrical coordinates. The texture just wraps

around the cylinder.around the cylinder. Image is bent into a cylinder Image is bent into a cylinder

before projection takes place. Object is then placed before projection takes place. Object is then placed

‘in’ the cylinder‘in’ the cylinder

Applying a texture map to a cylinder is easy if we use Applying a texture map to a cylinder is easy if we use cylindrical coordinates. The texture just wraps cylindrical coordinates. The texture just wraps

around the cylinder.around the cylinder. Image is bent into a cylinder Image is bent into a cylinder

before projection takes place. Object is then placed before projection takes place. Object is then placed

‘in’ the cylinder‘in’ the cylinder

More examples on cylindrical mapping

Rectangular Cylindrical Mapping

Spherical Mapping

We can apply a texture map to a sphere by using We can apply a texture map to a sphere by using spherical coordinates. Image bent onto an spherical coordinates. Image bent onto an imaginary sphere before projection. imaginary sphere before projection.

Object placed ‘in’ sphere Object placed ‘in’ sphere

We can apply a texture map to a sphere by using We can apply a texture map to a sphere by using spherical coordinates. Image bent onto an spherical coordinates. Image bent onto an imaginary sphere before projection. imaginary sphere before projection.

Object placed ‘in’ sphere Object placed ‘in’ sphere

More Spherical Mapping

Planar Mapping

a planar projection on a cube will have one side a planar projection on a cube will have one side mapped with the texture while the other sides show the mapped with the texture while the other sides show the texture streakedtexture streaked

a planar projection on a cube will have one side a planar projection on a cube will have one side mapped with the texture while the other sides show the mapped with the texture while the other sides show the texture streakedtexture streaked

Parameterised mapping• Imagine printing the texture image onto thin transparent film Imagine printing the texture image onto thin transparent film

• Then stretch the film over the surface Then stretch the film over the surface

• This is the principle of parameterised texture mapping This is the principle of parameterised texture mapping

• The 2D texture image is an array of rectangular pixels The 2D texture image is an array of rectangular pixels

• These can be referenced by Cartesian coordinates, usually with the lower left pixel being (0,0) These can be referenced by Cartesian coordinates, usually with the lower left pixel being (0,0) (and for a 512 x 512 image the top right being (511,511)) (and for a 512 x 512 image the top right being (511,511))

• Each pixel rectangle is then mapped to a corresponding area of the 3D surface Each pixel rectangle is then mapped to a corresponding area of the 3D surface

• You therefore have to divide the surface into the same number of steps You therefore have to divide the surface into the same number of steps

• The surface patch is defined to use the coordinate system U and V to specify locations on it The surface patch is defined to use the coordinate system U and V to specify locations on it

• The area defined by (0,0) on the surface has the color applied to it from the image pixel at (0,0) The area defined by (0,0) on the surface has the color applied to it from the image pixel at (0,0)

• Imagine printing the texture image onto thin transparent film Imagine printing the texture image onto thin transparent film

• Then stretch the film over the surface Then stretch the film over the surface

• This is the principle of parameterised texture mapping This is the principle of parameterised texture mapping

• The 2D texture image is an array of rectangular pixels The 2D texture image is an array of rectangular pixels

• These can be referenced by Cartesian coordinates, usually with the lower left pixel being (0,0) These can be referenced by Cartesian coordinates, usually with the lower left pixel being (0,0) (and for a 512 x 512 image the top right being (511,511)) (and for a 512 x 512 image the top right being (511,511))

• Each pixel rectangle is then mapped to a corresponding area of the 3D surface Each pixel rectangle is then mapped to a corresponding area of the 3D surface

• You therefore have to divide the surface into the same number of steps You therefore have to divide the surface into the same number of steps

• The surface patch is defined to use the coordinate system U and V to specify locations on it The surface patch is defined to use the coordinate system U and V to specify locations on it

• The area defined by (0,0) on the surface has the color applied to it from the image pixel at (0,0) The area defined by (0,0) on the surface has the color applied to it from the image pixel at (0,0)

Parametrization

Each (x,y) vertex in the destination polygon is the Each (x,y) vertex in the destination polygon is the projected (u,v) vertex from the source polygon. projected (u,v) vertex from the source polygon. The projected (x,y) pixels drawn in the destination The projected (x,y) pixels drawn in the destination polygon are taken from the corresponding polygon are taken from the corresponding

original (u,v) pixels in the source polygon.original (u,v) pixels in the source polygon.

Each (x,y) vertex in the destination polygon is the Each (x,y) vertex in the destination polygon is the projected (u,v) vertex from the source polygon. projected (u,v) vertex from the source polygon. The projected (x,y) pixels drawn in the destination The projected (x,y) pixels drawn in the destination polygon are taken from the corresponding polygon are taken from the corresponding

original (u,v) pixels in the source polygon.original (u,v) pixels in the source polygon.

ParametrizationDDefine a mapping from object space (x,y,z) to efine a mapping from object space (x,y,z) to texture space (s,t). texture space (s,t).

DDefine a mapping from object space (x,y,z) to efine a mapping from object space (x,y,z) to texture space (s,t). texture space (s,t).

Parameterised mapping Example scene without textures Same scene with textures appliedExample scene without textures Same scene with textures applied Example scene without textures Same scene with textures appliedExample scene without textures Same scene with textures applied

Texture Mapping in Terms of the Shading Equation

Texture mapping can be used to alter some or all Texture mapping can be used to alter some or all of the constants in the shading equation. We of the constants in the shading equation. We can simply use the texture as the final color for can simply use the texture as the final color for the pixel, we can just use it as diffuse color, or the pixel, we can just use it as diffuse color, or we can use the texture to alter the normal.we can use the texture to alter the normal.

Texture mapping can be used to alter some or all Texture mapping can be used to alter some or all of the constants in the shading equation. We of the constants in the shading equation. We can simply use the texture as the final color for can simply use the texture as the final color for the pixel, we can just use it as diffuse color, or the pixel, we can just use it as diffuse color, or we can use the texture to alter the normal.we can use the texture to alter the normal.

Texture Mapping in Terms of the Shading Equation

The resultThe result

Sphere Texture Map I = Texture(s,t) CSphere Texture Map I = Texture(s,t) Cdd = Texture(s,t) = Texture(s,t)

The resultThe result

Sphere Texture Map I = Texture(s,t) CSphere Texture Map I = Texture(s,t) Cdd = Texture(s,t) = Texture(s,t)

Bump Mapping

--Texture map can be used to alter the surface normal of an object. Texture map can be used to alter the surface normal of an object.

-The actual shape of the surface is unchanged. -The actual shape of the surface is unchanged.

-It is only being shaded as if it were a different shape! -It is only being shaded as if it were a different shape!

-This technique is called bump mapping. -This technique is called bump mapping.

-The texture map is treated as a single-valued function which -The texture map is treated as a single-valued function which represents height. represents height.

--Texture map can be used to alter the surface normal of an object. Texture map can be used to alter the surface normal of an object.

-The actual shape of the surface is unchanged. -The actual shape of the surface is unchanged.

-It is only being shaded as if it were a different shape! -It is only being shaded as if it were a different shape!

-This technique is called bump mapping. -This technique is called bump mapping.

-The texture map is treated as a single-valued function which -The texture map is treated as a single-valued function which represents height. represents height.

Bump Mapping

Bump mapping can give the visual illusion of Bump mapping can give the visual illusion of the presence in the surface of small bumps, the presence in the surface of small bumps, holes, irregularities, carvings, engraving, holes, irregularities, carvings, engraving, scales, and so on; if managed efficiently, this scales, and so on; if managed efficiently, this can be achieved at a very small fraction of the can be achieved at a very small fraction of the rendering time that would be necessary for an rendering time that would be necessary for an object with similar characteristics modeled as object with similar characteristics modeled as

geometry.geometry.

Bump mapping can give the visual illusion of Bump mapping can give the visual illusion of the presence in the surface of small bumps, the presence in the surface of small bumps, holes, irregularities, carvings, engraving, holes, irregularities, carvings, engraving, scales, and so on; if managed efficiently, this scales, and so on; if managed efficiently, this can be achieved at a very small fraction of the can be achieved at a very small fraction of the rendering time that would be necessary for an rendering time that would be necessary for an object with similar characteristics modeled as object with similar characteristics modeled as

geometry.geometry.

Bump Mapping

Sphere w/ Texture Map Bump Map Sphere w/ Texture & Sphere w/ Texture Map Bump Map Sphere w/ Texture & Bump Bump Maps Maps

Sphere w/ Texture Map Bump Map Sphere w/ Texture & Sphere w/ Texture Map Bump Map Sphere w/ Texture & Bump Bump Maps Maps

Bump Mapping

Cylinder w/ Texture Map Bump Map Cylinder w/ Texture & Bump Cylinder w/ Texture Map Bump Map Cylinder w/ Texture & Bump Maps Maps

Cylinder w/ Texture Map Bump Map Cylinder w/ Texture & Bump Cylinder w/ Texture Map Bump Map Cylinder w/ Texture & Bump Maps Maps

Bump Mapping

Bump Mapping

Bump maps are good for subtle details like panel lines and rivets

Displacement Mapping

TThe texture map is used to actually move the surface point. he texture map is used to actually move the surface point.

This is called displacement mapping. This is fundamentally This is called displacement mapping. This is fundamentally different than bump mapping. This technique is like a texture different than bump mapping. This technique is like a texture map each pixel holding a displacement value.map each pixel holding a displacement value.

TThe texture map is used to actually move the surface point. he texture map is used to actually move the surface point.

This is called displacement mapping. This is fundamentally This is called displacement mapping. This is fundamentally different than bump mapping. This technique is like a texture different than bump mapping. This technique is like a texture map each pixel holding a displacement value.map each pixel holding a displacement value.

•Displacement shaders applied to a box and a sphere in a simple Displacement shaders applied to a box and a sphere in a simple scene. Accurate computation of shadows and refractions is scene. Accurate computation of shadows and refractions is illustratedillustrated

•Displacement shaders applied to a box and a sphere in a simple Displacement shaders applied to a box and a sphere in a simple scene. Accurate computation of shadows and refractions is scene. Accurate computation of shadows and refractions is illustratedillustrated

Depending on  values, the surface will appear dull and dirty or bright Depending on  values, the surface will appear dull and dirty or bright and clean. Works well for illustratingand clean. Works well for illustrating

grease grime and worn paintgrease grime and worn paint

Depending on  values, the surface will appear dull and dirty or bright Depending on  values, the surface will appear dull and dirty or bright and clean. Works well for illustratingand clean. Works well for illustrating

grease grime and worn paintgrease grime and worn paint

Diffusion MappingDiffusion Mapping

Color Mapping

These are full color images that are applied to the model's surface. Any These are full color images that are applied to the model's surface. Any markings or graphics are incorporated into the color map. The markings or graphics are incorporated into the color map. The completed model below wears a total of 131 texture maps.completed model below wears a total of 131 texture maps.

These are full color images that are applied to the model's surface. Any These are full color images that are applied to the model's surface. Any markings or graphics are incorporated into the color map. The markings or graphics are incorporated into the color map. The completed model below wears a total of 131 texture maps.completed model below wears a total of 131 texture maps.

Transparency Mapping

Texture mapping may be used to lay transparent or semi-Texture mapping may be used to lay transparent or semi-transparent objects over a scene by representing transparency transparent objects over a scene by representing transparency values in the texture image as well as color values. This technique values in the texture image as well as color values. This technique

is useful for simulating cloudsis useful for simulating clouds

[Gardner 85] and trees for [Gardner 85] and trees for

example, by drawing example, by drawing

appropriately textured polygons appropriately textured polygons

over a background.over a background.

Texture mapping may be used to lay transparent or semi-Texture mapping may be used to lay transparent or semi-transparent objects over a scene by representing transparency transparent objects over a scene by representing transparency values in the texture image as well as color values. This technique values in the texture image as well as color values. This technique

is useful for simulating cloudsis useful for simulating clouds

[Gardner 85] and trees for [Gardner 85] and trees for

example, by drawing example, by drawing

appropriately textured polygons appropriately textured polygons

over a background.over a background.

Light Mapping

Light maps are stored pre-computed lighting information that is Light maps are stored pre-computed lighting information that is mapped on to surfaces. Quake uses light maps in addition to texture mapped on to surfaces. Quake uses light maps in addition to texture maps.Both texture maps and light maps are multiplied together at maps.Both texture maps and light maps are multiplied together at run-time, and cached for efficiency. run-time, and cached for efficiency.

Light maps are stored pre-computed lighting information that is Light maps are stored pre-computed lighting information that is mapped on to surfaces. Quake uses light maps in addition to texture mapped on to surfaces. Quake uses light maps in addition to texture maps.Both texture maps and light maps are multiplied together at maps.Both texture maps and light maps are multiplied together at run-time, and cached for efficiency. run-time, and cached for efficiency.

Light Mapping

More ExamplesMore ExamplesMore ExamplesMore Examples

Noise and turbulence

We sometimes want to add random variations to our texture, We sometimes want to add random variations to our texture, but in a controlled way. but in a controlled way. NoiseNoise and and turbulenceturbulence are very useful are very useful tools for doing just that. tools for doing just that.

To calculate the noise value of any point in space, we first To calculate the noise value of any point in space, we first determine which cube of the lattice the point is in. Next, we determine which cube of the lattice the point is in. Next, we interpolate the values of the 8 corners of the cube: interpolate the values of the 8 corners of the cube:

We sometimes want to add random variations to our texture, We sometimes want to add random variations to our texture, but in a controlled way. but in a controlled way. NoiseNoise and and turbulenceturbulence are very useful are very useful tools for doing just that. tools for doing just that.

To calculate the noise value of any point in space, we first To calculate the noise value of any point in space, we first determine which cube of the lattice the point is in. Next, we determine which cube of the lattice the point is in. Next, we interpolate the values of the 8 corners of the cube: interpolate the values of the 8 corners of the cube:

Noise and turbulence

Original Object Trilinear Noise Triquadratic NoiseOriginal Object Trilinear Noise Triquadratic Noise Original Object Trilinear Noise Triquadratic NoiseOriginal Object Trilinear Noise Triquadratic Noise

Noise and turbulence

TurbulenceTurbulence

Noise is OK, but it’s not enough all by itself. It can be made more interesting by Noise is OK, but it’s not enough all by itself. It can be made more interesting by turbulenceturbulence. A simple turbulence function can be computed by summing many . A simple turbulence function can be computed by summing many different frequencies of noise functionsdifferent frequencies of noise functions

TurbulenceTurbulence

Noise is OK, but it’s not enough all by itself. It can be made more interesting by Noise is OK, but it’s not enough all by itself. It can be made more interesting by turbulenceturbulence. A simple turbulence function can be computed by summing many . A simple turbulence function can be computed by summing many different frequencies of noise functionsdifferent frequencies of noise functions

Noise and turbulenceMarble ExampleMarble Example

Turbulence can be used to generate Turbulence can be used to generate

beautiful 3D marble textures, such as beautiful 3D marble textures, such as

this marble vase created by Ken Perlin. this marble vase created by Ken Perlin.

The idea is simple. Fill space with black The idea is simple. Fill space with black

and white stripes, using a sine wave function. and white stripes, using a sine wave function.

Then use turbulence at each point to distort Then use turbulence at each point to distort

those planes. those planes.

Marble ExampleMarble Example

Turbulence can be used to generate Turbulence can be used to generate

beautiful 3D marble textures, such as beautiful 3D marble textures, such as

this marble vase created by Ken Perlin. this marble vase created by Ken Perlin.

The idea is simple. Fill space with black The idea is simple. Fill space with black

and white stripes, using a sine wave function. and white stripes, using a sine wave function.

Then use turbulence at each point to distort Then use turbulence at each point to distort

those planes. those planes.

Perspective CorrectionPerspective CorrectionTextures look fine, mapped to a polygon when viewed face-on. Textures look fine, mapped to a polygon when viewed face-on.

But if viewed at an angle, we can get perspective distortion. But if viewed at an angle, we can get perspective distortion.

The problem is that texture coordinates do not vary linearly in screen space. The problem is that texture coordinates do not vary linearly in screen space.

If we interpolate texture coordinates linearly in screen space, we get the image on left left below, when If we interpolate texture coordinates linearly in screen space, we get the image on left left below, when what we would like is the image on the right. what we would like is the image on the right.

Textures look fine, mapped to a polygon when viewed face-on. Textures look fine, mapped to a polygon when viewed face-on.

But if viewed at an angle, we can get perspective distortion. But if viewed at an angle, we can get perspective distortion.

The problem is that texture coordinates do not vary linearly in screen space. The problem is that texture coordinates do not vary linearly in screen space.

If we interpolate texture coordinates linearly in screen space, we get the image on left left below, when If we interpolate texture coordinates linearly in screen space, we get the image on left left below, when what we would like is the image on the right. what we would like is the image on the right.

Perspective CorrectionPerspective Correction

Perspective Distortion Perspective CorrectionPerspective Distortion Perspective Correction Perspective Distortion Perspective CorrectionPerspective Distortion Perspective Correction

SamplingSampling

Textures look pretty good when the size of the texture map is about the same size as the polygon on the screenTextures look pretty good when the size of the texture map is about the same size as the polygon on the screen

Polygon Texture Polygon Texture Map Polygon Map Polygon w/ Texture Mapw/ Texture Map

Textures look pretty good when the size of the texture map is about the same size as the polygon on the screenTextures look pretty good when the size of the texture map is about the same size as the polygon on the screen

Polygon Texture Polygon Texture Map Polygon Map Polygon w/ Texture Mapw/ Texture Map

SamplingSampling

But if we zoom in too close, many pixels on the screen map to the same texel. If we select the closest texel, we get the image on the But if we zoom in too close, many pixels on the screen map to the same texel. If we select the closest texel, we get the image on the left below. We can do better by bilinearly interpolating the 4 texels surrounding the sample, which gives us the image on the right left below. We can do better by bilinearly interpolating the 4 texels surrounding the sample, which gives us the image on the right

below.below.

But if we zoom in too close, many pixels on the screen map to the same texel. If we select the closest texel, we get the image on the But if we zoom in too close, many pixels on the screen map to the same texel. If we select the closest texel, we get the image on the left below. We can do better by bilinearly interpolating the 4 texels surrounding the sample, which gives us the image on the right left below. We can do better by bilinearly interpolating the 4 texels surrounding the sample, which gives us the image on the right

below.below.

Mip MappingMip Mapping

Zooming out brings a problem such as trying to display high frequencies in the texture with too small of a sampling rate. Zooming out brings a problem such as trying to display high frequencies in the texture with too small of a sampling rate.

The solution is to pre-filter the texture. The solution is to pre-filter the texture.

A mip-map is a series of down-sampled versions of a texture, each at half the resolution of the previous. Each texture lookup A mip-map is a series of down-sampled versions of a texture, each at half the resolution of the previous. Each texture lookup is performed at the appropriate mip-map level, based on the size of the pixel projected into texture space. is performed at the appropriate mip-map level, based on the size of the pixel projected into texture space.

Zooming out brings a problem such as trying to display high frequencies in the texture with too small of a sampling rate. Zooming out brings a problem such as trying to display high frequencies in the texture with too small of a sampling rate.

The solution is to pre-filter the texture. The solution is to pre-filter the texture.

A mip-map is a series of down-sampled versions of a texture, each at half the resolution of the previous. Each texture lookup A mip-map is a series of down-sampled versions of a texture, each at half the resolution of the previous. Each texture lookup is performed at the appropriate mip-map level, based on the size of the pixel projected into texture space. is performed at the appropriate mip-map level, based on the size of the pixel projected into texture space.

Mip MappingMip Mapping

Point SamplingPoint Sampling Mip-MappingMip-MappingPoint SamplingPoint Sampling Mip-MappingMip-Mapping

Cellular TexturesCellular Textures

Image from Cellular Texture Generation, by Kurt Fleischer, David Laidlaw, Image from Cellular Texture Generation, by Kurt Fleischer, David Laidlaw, Bena Currin, and Alan Barr, SIGGRAPH '95Bena Currin, and Alan Barr, SIGGRAPH '95

Image from A Cellular Texture Basis Function, Image from A Cellular Texture Basis Function, by Steven Worley, SIGGRAPHby Steven Worley, SIGGRAPH '96'96

Environment MappingEnvironment mapping is a technique that simulates the Environment mapping is a technique that simulates the results of ray-tracing. Because environment mapping is results of ray-tracing. Because environment mapping is performed using texture mapping hardware, it can performed using texture mapping hardware, it can obtain global reflection and lighting results in real-time. obtain global reflection and lighting results in real-time.

Environment mapping is essentially the process of pre-Environment mapping is essentially the process of pre-computing a texture map and then sampling texels from computing a texture map and then sampling texels from this texture during the rendering of a model. The texture this texture during the rendering of a model. The texture

map is a projection of 3D space to 2D spacemap is a projection of 3D space to 2D space..

Environment mapping is a technique that simulates the Environment mapping is a technique that simulates the results of ray-tracing. Because environment mapping is results of ray-tracing. Because environment mapping is performed using texture mapping hardware, it can performed using texture mapping hardware, it can obtain global reflection and lighting results in real-time. obtain global reflection and lighting results in real-time.

Environment mapping is essentially the process of pre-Environment mapping is essentially the process of pre-computing a texture map and then sampling texels from computing a texture map and then sampling texels from this texture during the rendering of a model. The texture this texture during the rendering of a model. The texture

map is a projection of 3D space to 2D spacemap is a projection of 3D space to 2D space..

Environment mapping

Environment mapping [Greene 86] may be achieved through texture Environment mapping [Greene 86] may be achieved through texture mapping in one of two ways.mapping in one of two ways.

First way is through texture mapping requiring six texture images, First way is through texture mapping requiring six texture images, each corresponding to a face of a cube, that represent the each corresponding to a face of a cube, that represent the surrounding environment. surrounding environment.

Environment mapping [Greene 86] may be achieved through texture Environment mapping [Greene 86] may be achieved through texture mapping in one of two ways.mapping in one of two ways.

First way is through texture mapping requiring six texture images, First way is through texture mapping requiring six texture images, each corresponding to a face of a cube, that represent the each corresponding to a face of a cube, that represent the surrounding environment. surrounding environment.

Environment mapping

At each vertex, a reflection vector is computed. At each vertex, a reflection vector is computed.

This reflection vector indexes one of the six texture This reflection vector indexes one of the six texture images. images.

The image is mapped onto the polygon using projective The image is mapped onto the polygon using projective texturing. texturing.

If a polygon has reflections into more than one face of If a polygon has reflections into more than one face of the cube, then the polygon is subdivided into pieces, the cube, then the polygon is subdivided into pieces, each of which generates reflections into only one faceeach of which generates reflections into only one face

At each vertex, a reflection vector is computed. At each vertex, a reflection vector is computed.

This reflection vector indexes one of the six texture This reflection vector indexes one of the six texture images. images.

The image is mapped onto the polygon using projective The image is mapped onto the polygon using projective texturing. texturing.

If a polygon has reflections into more than one face of If a polygon has reflections into more than one face of the cube, then the polygon is subdivided into pieces, the cube, then the polygon is subdivided into pieces, each of which generates reflections into only one faceeach of which generates reflections into only one face

Environment mapping

The second method is to generate a single texture image of a The second method is to generate a single texture image of a perfectly reflecting sphere in the environment. This image consists perfectly reflecting sphere in the environment. This image consists of a circle representing the hemisphere of the environment behind of a circle representing the hemisphere of the environment behind the viewer.the viewer.

The second method is to generate a single texture image of a The second method is to generate a single texture image of a perfectly reflecting sphere in the environment. This image consists perfectly reflecting sphere in the environment. This image consists of a circle representing the hemisphere of the environment behind of a circle representing the hemisphere of the environment behind the viewer.the viewer.

Solid Mapping

Mapping a solid texture onto a solid object is a fairly straighforward Mapping a solid texture onto a solid object is a fairly straighforward idea but proved to be challenging to implement. We represent idea but proved to be challenging to implement. We represent volume data by creating z files, representing parallel slices, of size volume data by creating z files, representing parallel slices, of size x by y, where x, y, and z are the dimensions of the volume. The data x by y, where x, y, and z are the dimensions of the volume. The data we used was in ppm format for easy reading. we used was in ppm format for easy reading.

Mapping a solid texture onto a solid object is a fairly straighforward Mapping a solid texture onto a solid object is a fairly straighforward idea but proved to be challenging to implement. We represent idea but proved to be challenging to implement. We represent volume data by creating z files, representing parallel slices, of size volume data by creating z files, representing parallel slices, of size x by y, where x, y, and z are the dimensions of the volume. The data x by y, where x, y, and z are the dimensions of the volume. The data we used was in ppm format for easy reading. we used was in ppm format for easy reading.

Questions

1- What are the ways to generate a texture?1- What are the ways to generate a texture?

Textures may be ‘real’, manually generated or procedurally Textures may be ‘real’, manually generated or procedurally

generated. generated.

2- What is the use of light maps?2- What is the use of light maps?

Light maps are stored pre-computed lighting information that is Light maps are stored pre-computed lighting information that is

mapped on to surfacesmapped on to surfaces

3- Does the actual shape of the object change in “Bump Mapping”?3- Does the actual shape of the object change in “Bump Mapping”?

No, the actual shape of the surface is unchanged. No, the actual shape of the surface is unchanged.

It is only being shaded as if it were a different shape!It is only being shaded as if it were a different shape!

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