Shading

Shading:

Shading, shadows

• How do we use ray to determine shade of pixel?
• At closest intersection point, perform Phong shading.

  Gives essentially the same images as standard polygon renderer, but with more primitives.

• Idea: Before adding contribution from a light, cast ray to light.
  • If ray hits another object before hitting light, then don't perform shading calculation.
  • This gives shadows.

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Shading:

Reflections

• Idea: Cast a ray in the mirror direction.
• Add the colour coming from this ray to the shade of the initial ray.
• This gives mirror reflections

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• We perform a full lighting calculation at the first intersection of this reflected ray.
• If we send another reflected ray from here, when do we stop?
  • Answer 1: Stop at a fixed depth.
  • Answer 2: Accumulate product of reflection coefficients and stop when this product is too small.
• Refraction similar