3D graphics eBook - Course Materials Repository

Procedural texture 124
References
[1] http:/ / www. spiralgraphics. biz/ gallery. htm
[2] Ebert et al: Texturing and Modeling A Procedural Approach, page 10. Morgan Kaufmann, 2003.
[3] Ebert et al: Texturing and Modeling A Procedural Approach, page 135. Morgan Kaufmann, 2003.
[4] Ebert et al: Texturing and Modeling A Procedural Approach, page 547. Morgan Kaufmann, 2003.
[5] http:/ / www. photoshoproadmap. com
Some programs for creating textures using Procedural texturing
• Allegorithmic Substance
• Filter Forge
• Genetica (program) (http:/ / www. spiralgraphics. biz/ genetica. htm)
• DarkTree (http:/ / www. darksim. com/ html/ dt25_description. html)
• Context Free Art (http:/ / www. contextfreeart. org/ index. html)
• TexRD (http:/ / www. texrd. com) (based on reaction-diffusion: self-organizing textures)
• Texture Garden (http:/ / texturegarden. com)
• Enhance Textures (http:/ / www. shaders. co. uk)
3D projection
3D projection is any method of mapping three-dimensional points to a two-dimensional plane. As most current
methods for displaying graphical data are based on planar two-dimensional media, the use of this type of projection
is widespread, especially in computer graphics, engineering and drafting.
Orthographic projection
When the human eye looks at a scene, objects in the distance appear smaller than objects close by. Orthographic
projection ignores this effect to allow the creation of to-scale drawings for construction and engineering.
Orthographic projections are a small set of transforms often used to show profile, detail or precise measurements of a
three dimensional object. Common names for orthographic projections include plane, cross-section, bird's-eye, and
elevation.
If the normal of the viewing plane (the camera direction) is parallel to one of the primary axes (which is the x, y, or z
axis), the mathematical transformation is as follows; To project the 3D point , , onto the 2D point ,
using an orthographic projection parallel to the y axis (profile view), the following equations can be used:
where the vector s is an arbitrary scale factor, and c is an arbitrary offset. These constants are optional, and can be
used to properly align the viewport. Using matrix multiplication, the equations become:
.
While orthographically projected images represent the three dimensional nature of the object projected, they do not
represent the object as it would be recorded photographically or perceived by a viewer observing it directly. In
particular, parallel lengths at all points in an orthographically projected image are of the same scale regardless of
whether they are far away or near to the virtual viewer. As a result, lengths near to the viewer are not foreshortened
as they would be in a perspective projection.