Ray Casting and Rasterization - Computer Graphics: Principles and Practice - page 400

(although one can typically determine its gamma exponent) or the exact viewing
conditions of the room, so precise color correction and tone mapping is beyond
our ability here. However, the simple act of applying gamma correction arguably
captures some of the most important aspects of that process and is computationally
inexpensive and robust.

Inline Exercise 15.3: Two images are shown below. Both have been gamma-
encoded with

= 2.0 for printing and online display. The image on the left is
a gradient that has been rendered to give the impression of linear brightness .
It should appear as a linear color ramp. The image on the right was rendered
with linear radiance (it is the checkerboard on the right of Figure 15.2 without
the blue squares). It should appear as a nonlinear color ramp. The image was
rendered at 200

γ

200 pixels. What equation did we use to compute the value
(in [ 0, 1 ] ) of the pixel at ( x , y ) for the gradient image on the left?

×

Linear brightness Linear radiance

15.3.3 Scene Representation
Listing 15.7 shows a Triangle class. It stores each triangle by explicitly storing
each vertex. Each vertex has an associated normal that is used exclusively for
shading; the normals do not describe the actual geometry. These are sometimes
called shading normals. When the vertex normals are identical to the normal
to the plane of the triangle, the triangle's shading will appear consistent with its
actual geometry. When the normals diverge from this, the shading will mimic that
of a curved surface. Since the silhouette of the triangle will still be polygonal, this
effect is most convincing in a scene containing many small triangles.

Listing 15.7: Interface for a Triangle class.

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class Triangle {
private :
Point3

m_vertex[3];

Vector3 m_normal[3];

BSDF m_bsdf;

public :

const Point3 & vertex( int i) const { return m_vertex[i]; }
const Vector3 & normal( int i) const { return m_normal[i]; }
const BSDF & bsdf() const { return m_bsdf; }
...

};

We also associate a BSDF class value with each triangle. This describes the
material properties of the surface modeled by the triangle. It is described in Sec-
tion 15.4.5. For now, think of this as the color of the triangle.