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PRIMITIVES

Advanced Computer Graphics

SEMINAR 2

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Primitive Shading

  • Light source located at camera position
  • Lower light intensity of distant objects
  • Creates illusion of depth

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Double intensity = MaxIntensity / ray.HitParam;

return ray.HitModel.Color * intensity;

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zNear & zFar

  • Objects too close to camera would block all visible space
      • zNear clips objects too close
  • Objects too far from camera are negligibly small
      • zFar clips invisible objects
  • Why z?

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Bias

 

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ray

camera

sun

shadow

ray

P – intersection point

sphere

Unexpected intersections

Can be corrected with bias

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AABB (Axis Aligned Bounding Box)

 

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AABB – intersection parameters

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2D case:

 

For x coordinate:

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AABB checking for intersection

 

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Ring (3D Circle)

 

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Sphere

  • Defined by a center point C and radius R
  • Intersection point can be solved analytically or geometrically

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Sphere – Geometric Solution

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C

P

P’

O

 

d

R

 

 

tca

thc

 

 

L

t1

t0

r

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Sphere – Analytical Solution

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where:

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Triangle

  • Defined by three points A, B, C
  • Intersection can be found using barycentric coordinates

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where:

 

 

If ray intersects triangle they have a common point:

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Template Assignment

  • Define primitive objects, similarly to Plane
      • Add class Sphere
      • Add class AABB
      • Add class Circle

​

  • Bonus
      • Add class Triangle
      • Add class Cylinder
      • Add class Cone

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