This document discusses two methods for adding shadows to objects in 3D scenes - shadows as textures and creating shadows with a shadow buffer. The shadows as textures method works for point light sources casting shadows on flat surfaces by "painting" the shadows as textures, but requires computing the shape of each shadow. The shadow buffer method performs hidden surface removal by marking in a buffer any points hidden from the light source, then rendering the scene in two passes - first loading the shadow buffer and then rendering using the buffer values to determine shading.

1. Adding shadows ofAdding shadows of
objectsobjects
Aravindhan A
Final year CSE | SMIT
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2. Why shadows?

Make image more realistic

Visual clues as how objects are positioned with
respect to each other

4. Two methods

Shadows as Texture

Creating shadows with the use of a shadow
buffer

5. Shadows as Texture

The technique of “painting” shadows as a
texture works for shadows that are cast

On a flat surface by a point light source

Problem is to compute the shape of shadow
that is cast

6. Computing shape of shadow

7. Creating shadows with shadow
buffer

This method performs removal of hidden
surfaces

Principle: Any point in a scene that are hidden
from the light source must in shadow

8. Creating shadows with shadow
buffer

Rendering is done in two stages,
1) Loading the shadow buffer
2) Rendering the scene

9. Loading the shadow buffer

Shadow buffer calculation is independent of
eye position

Shadow buffer must be recalculated and loaded
whenever the objects move relative to the light
source

10. Rendering the scene

Each face of the screen is rendered using eye
camera
1) Pseudo depth from the source to point P
2) Index location in shadow buffer
3) Value stored at index location in shadow buffer

12. Thank you!