// File: outline.txt
// Desc: Vertex shader renders silhouette edges.
//
// Globals
//
extern matrix WorldViewMatrix;
extern matrix ProjMatrix;
static vector Black = {0.0f, 0.0f, 0.0f, 0.0f};
//
// Structures
//
struct VS_INPUT
{
vector position : POSITION;
vector normal : NORMAL0;
vector faceNormal1 : NORMAL1;
vector faceNormal2 : NORMAL2;
};
struct VS_OUTPUT
{
vector position : POSITION;
vector diffuse : COLOR;
};
//
// Main
//
VS_OUTPUT Main(VS_INPUT input)
{
// zero out each member in output
VS_OUTPUT output = (VS_OUTPUT)0;
// transform position to view space
input.position = mul(input.position, WorldViewMatrix);
// Compute a vector in the direction of the vertex
// from the eye. Recall the eye is at the origin
// in view space - eye is just camera position.
Introduction to Vertex Shaders 315
Part IV
vector eyeToVertex = input.position;
// transform normals to view space. Set w
// components to zero since we're transforming vectors.
// Assume there are no scalings in the world
// matrix as well.
input.normal.w = 0.0f;
input.faceNormal1.w = 0.0f;
input.faceNormal2.w = 0.0f;
input.normal = mul(input.normal, WorldViewMatrix);
input.faceNormal1 = mul(input.faceNormal1, WorldViewMatrix);
input.faceNormal2 = mul(input.faceNormal2, WorldViewMatrix);
// compute the cosine of the angles between
// the eyeToVertex vector and the face normals.
float dot0 = dot(eyeToVertex, input.faceNormal1);
float dot1 = dot(eyeToVertex, input.faceNormal2);
// if cosines are different signs (positive/negative)
// then we are on a silhouette edge. Do the signs
// differ?
if( (dot0 * dot1) < 0.0f )
{
// yes, then this vertex is on a silhouette edge,
// offset the vertex position by some scalar in the
// direction of the vertex normal.
input.position += 0.1f * input.normal;
}
// transform to homogeneous clip space
output.position = mul(input.position, ProjMatrix);
// set outline color
output.diffuse = Black;
return output;
}

// Globalsextern matrix vertexTransform;extern matrix normalTransform;extern vector colour;// Structuresstruct VS_INPUT{    vector position : POSITION;    vector normal: NORMAL;};struct VS_OUTPUT{    vector position : POSITION;    vector diffuse  : COLOR;};// MainVS_OUTPUT Main(VS_INPUT input){	// zero out each member in output	VS_OUTPUT output = (VS_OUTPUT)0;	 input.position.x *= 1.05f;	 input.position.y *= 1.05f;	 input.position.z *= 1.05f;   	output.position = mul(input.position, vertexTransform);   	input.normal.w   = 0.0f;   	input.normal     = mul(input.normal,normalTransform);   	input.normal.x = -input.normal.x;   	input.normal.y = -input.normal.y;   	input.normal.z = -input.normal.z;       	// save color    	output.diffuse = colour;        	return output;}