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Texture Filtering
MipMaps
“Optimal” case
Minification Magnification
Pixel Footprint
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Exploring Texture Filtering & Environment Maps: MipMaps, Anisotropic Filtering & Billboard, Assignments of Computer Science
This document delves into the concepts of texture filtering, specifically focusing on mipmaps, anisotropic filtering, and billboards. Topics include pyramid textures, linear vs. Nearest filtering, trilinear filtering, anisotropic filtering, environment maps, spherical environment maps, parabolic environment maps, cube environment maps, and billboards. The document also covers the works of gene miller, gerri's game, and paul debevec, as well as techniques like lightmaps and opengl lighting.
Typology: Assignments
Pre 2010
1 / 9
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Texture Filtering
MipMaps
“Optimal” case
Minification Magnification
Pixel Footprint
Pyramid Textures (Mipmapping)
Linear vs. Nearest
Trilinear Anisotropic
Gene Miller In practice
• Shiny spheres
Gene Miller
• Interface
(L. Williams 1985)
• Terminator 2 (1991)
Gerri’s Game Story of Reflection Mapping
Spherical Environment Maps
• Pros:
– Single texture (no “if’s”)
– Triangles don’t span texture boundaries
- Per-vertex computation!
• Cons:
– Bad sampling
– Only works for single
viewpoint / view direction
Parabolic Environment Maps
Parabolic Environment Maps Nayar ‘
Cube Environment Maps
• Per-fragment
• Suported in HW
• No warp
(perspective maps)
Nvidia Cube Mapping
Billboards
up = arbitrary axis look = camera_pos - point_pos; right = up x look; look = right x up;
Billboards Hack
• Trees don’t face camera
Billboards Hack
• Trees don’t face
camera
• Use the Modelview
• Set rotation to identity
Billboards Hack 2
• Trees don’t face
camera
• Use the Modelview
• Make billboard
cylindrical
• Set part of rotation to
identity
Billboards Hack 3
- Modify the verticies of the
Billboard quad
- Reverses the orientations
in the Modelview Maxtrix
- Draw quad using right/up
offsets
+ only get modelview once
- Must xform all verticies
right (^) up
Billboards Correct
• Trees face camera
Billboards Correct
• Trees face camera
• Need
- Object in world coords
- Target position in world coords
• Assume
Right = [1,0,0]
Up = [0,1,0]
LookAt = [0,0,1]
Billboards Correct
Billboards Correct
objToCamProj is the projection to the XZ plane (y=0)
**1. Normalize objToCamProj
- aux=LookAt dot objToCamProj
- Up’= lookAt X objToCamProj
- glRotate(acos(aux), Up’[0], Up’[1], Up’[2]**
Billboards Correct
objToCamProj is the projection to the XZ plane (y=0)
**1. Normalize objToCamProj
- aux=LookAt dot objToCamProj
- Up’= lookAt X objToCamProj
- glRotate(acos(aux), Up’[0], Up’[1], Up’[2]**
Billboards Correct
objToCamProj is the projection to the XZ plane (y=0)
**1. Normalize objToCamProj
- aux=LookAt dot objToCamProj
- Up’= lookAt X objToCamProj
- glRotate(acos(aux), Up’[0], Up’[1], Up’[2]**
Tilt towards Camera
**1. Aux’= objToCamProj dot objToCam
- glRotate(acos(aux’), right[0], right[1],** right[2])
Billboards Correct
Object Position
objPosWC = camPos + (M1-1) * V