CS 380 - GPU and GPGPU ProgrammingLecture 14: GPU Texturing 2

Markus Hadwiger, KAUST

2

Reading Assignment #9 (until Oct 29)

Read (required):

• Rational-Linear Interpolation of Texture Coordinates and Their PartialDerivatives

http://www.hpl.hp.com/techreports/98/HPL-98-113.pdf

• OpenGL 4.6 Core Specification,Chapter 9 (Frame Buffers and Frame Buffer Objects)

https://www.khronos.org/registry/OpenGL/specs/gl/glspec46.core.pdf

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Programming Assignments: Schedule (tentative)

Assignment #1:

• Querying the GPU (OpenGL and CUDA) due Aug 27

----- Eid Break: Aug 31 – Sep 7 -----

Assignment #2:

• Phong shading and procedural texturing (GLSL) due Oct 1

• OpenGL + GLSL Tutorial: this week

Assignment #3:

• Image Processing with (a) GLSL, and (b) CUDA due Oct 22

Assignment #4:

• Linear Algebra (CUDA) due Nov 12

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Quiz #2: Nov 1

Organization

• First 30 min of lecture

• No material (book, notes, ...) allowed

Content of questions

• Lectures (both actual lectures and slides)

• Reading assigments

• Programming assignments (algorithms, methods)

• Solve short practical examples

Next Lectures

Lecture 15: Thursday, Oct 26, 9:00

Markus Hadwiger, KAUST 5

6

GPU Texturing

Rage / id Tech 5 (id Software)

Eduard Gröller, Stefan Jeschke 7

Texturing: General Approach

Texture space (u,v) Object space (xO,yO,zO) Image Space (xI,yI)

Parametrization Rendering(Projection etc.)

Texels

8

Perspective Projection

9

Perspective Projection

10

Perspective Projection

11

Perspective Projection

12

Perspective Projection

13

Perspective Projection

Vienna University of Technology 14

Perspective Texture Mapping

2

2

1

1

21

21

w

xb

w

xa

bwaw

bxax

linear interpolation

in object space

a = b = 0.5

linear interpolationin screen space

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Early Perspective Texture Mapping in Games

DOOM (id Software, 1993)

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Early Perspective Texture Mapping in Games

Quake (id Software, 1996)

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Perspective Projection

Vienna University of Technology 18

Perspective Texture Mapping

Solution: interpolate (s/w, t/w, 1/w)

(s/w) / (1/w) = s etc. at every fragment

each vertex

each fragment

Heckbert and Moreton

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Perspective-Correct Interpolation Recipe

Heckbert and Moreton

2D Texture Mapping

Texture

R G B AFor each fragment:

interpolate thetexture coordinates

(barycentric)Or:

Use arbitrary, computed coordinates

Texture-Lookup:interpolate thetexture data(bi-linear)

Or:Nearest-neighbor for “array lookup”

3D Texture Mapping

R G B A

R

GB

For each fragment:interpolate the

texture coordinates(barycentric)

Or:Use arbitrary, computed coordinates

Texture-Lookup:interpolate thetexture data(tri-linear)

Or:Nearest-neighbor for “array lookup”

Thank you.