Please enable JavaScript.
Coggle requires JavaScript to display documents.
Surface Rendering & Shading (Light source models (Point Source: All…
Surface Rendering & Shading
displacement mapping
Displaces each point on the surface. Texture values gives amount to move in direction normal to surface.
Light source models
Point Source: All light rays originate at a point and radially
diverge.
Parallel source: Light rays are all parallel. May be modelled as a point source at infinite distance (the sun).
Distributed source: All light rays originate at a finite area in space. It models a nearby source, such as a fluorescent light.
definition
Illumination - how light source interacts w/ object surfaces
shading : given illumination, how to render faces of polygons
shading tech
• Flat Shading: No interpolation
same values are used to render the entire polygon
Misses out on shading variations.
faster, simpler
Suitable when:
polygon too small
too far away
Mach Band effect
Exaggerates the contrast between edges of the slightly differing
shades of a colour, as soon as they contact one another
Triggered by edge-detection enabled by the human eye, it
accentuates the discontinuity at the boundary
• Smooth Shading: Linear change (interpolation)
lighting is computed at multiple points on
each polygon. thus, avoid Mach Band effect
Phong Shading
similar to Gouraud
interpolates surface normals
full shading calculation at every pixel using interpolated normals
much slower than Gouraud
better at highlights than Gouraud
procedure:
normal at each polygon vertex (average of the
normal of adjacent faces)
Linearly interpolate the vertex normals over the surface polygon
Apply the illumination model along each scan line to calculate
intensity of each surface point
Gouraud Shading
Lighting per each polygon
vertex
Color interpolation for interior pixels
assumption: Linear change between vertices
high curvature in polygon -> inaccurate shading
procedure
calc normal at each polygon vertex
Apply an illumination model to each vertex to calculate the
vertex intensity
Linearly interpolate the vertex intensities over the surface
polygon
Cel / toon shading
non-realistic shading
technique aimed at making objects look like comic books.
texture mapping
maps planar image (typically 2D) onto a three dimensional object, adding visual detail.
texture < surface
replicate -> not natural
not replicate -> not cover whole surface
texture synthesis can address, but only on random looking textures
need to correctly align them.
bump mapping
generate rough surfaces w/out increasing # of poly. (can add realism)
surface not change, bbut looked like it did. convincing from a distance, not so much when close.