Ray Casting and Rasterization - Computer Graphics: Principles and Practice - page 437

Listing 15.31 shows how this code is used to model the triangle-and-ground-
plane scene. In it, the process of uploading the geometry to the graphics device is
entirely abstracted within the Mesh class.

Listing 15.31: Host code to create indexed triangle meshes for the
triangle-plus-ground scene.

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void makeTrianglePlusGroundScene(MeshScene& s) {
std::vector< Vector3 > vertex, normal;
std::vector<int> index;

// Green triangle geometry
vertex.push_back( Point3 (0,1,-2)); vertex.push_back( Point3 (-1.9f,-1,-2));
vertex.push_back( Point3 (1.6f,-0.5f,-2));
normal.push_back( Vector3 (0,0.6f,1).direction()); normal.
push_back( Vector3 (-0.4f,-0.4f, 1.0f).direction()); normal.
push_back( Vector3 (0.4f,-0.4f, 1.0f).direction());
index.push_back(0); index.push_back(1); index.push_back(2);
index.push_back(0); index.push_back(2); index.push_back(1);
shared_ptr< BSDF > greenBSDF(new PhongBSDF( Color3 ::green() * 0.8f,
Color3 ::white() * 0.2f, 100));

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s.meshArray.push_back(Mesh(vertex, normal, index, greenBSDF));
vertex.clear(); normal.clear(); index.clear();

/////////////////////////////////////////////////////////
// Ground plane geometry
const float groundY = -1.0f;
vertex.push_back( Point3 (-10, groundY, -10)); vertex.push_back( Point3 (-10,
groundY, -0.01f));
vertex.push_back( Point3 (10, groundY, -0.01f)); vertex.push_back( Point3 (10,
groundY, -10));

normal.push_back( Vector3 ::unitY()); normal.push_back( Vector3 ::unitY());
normal.push_back( Vector3 ::unitY()); normal.push_back( Vector3 ::unitY());

index.push_back(0); index.push_back(1); index.push_back(2);
index.push_back(0); index.push_back(2); index.push_back(3);

const Color3 groundColor = Color3 ::white() * 0.8f;
s.meshArray.push_back(Mesh(vertex, normal, index, groundColor));

//////////////////////////////////////////////////////////
// Light source
s.lightArray.resize(1);
s.lightArray[0].position = Vector3 (1, 3, 1);
s.lightArray[0].power = Color3 ::white() * 31.0f;

}

15.7.2.3 Creating Shaders
The vertex shader must transform the input vertex in global coordinates to a homo-
geneous point on the image plane. Listing 15.32 implements this transformation.
We chose to use the OpenGL Shading Language (GLSL). GLSL is representative
of other contemporary shading languages like HLSL, Cg, and RenderMan. All
of these are similar to C++. However, there are some minor syntactic differences
between GLSL and C++ that we call out here to aid your reading of this example.
In GLSL,