glm::vec2 end_tan(){
return(tans(1.0f));
}
//===== Compute Tangents Using Forward and Reverse Difference Method =====//
void herm_curve::comp_tans()
{
int i = 0;
float temp_dist1 = 0.0, temp_dist2 = 0.0;
Dyn_array_dbl dist_mag;
dist_mag.set_chunk_size(num_pnts);
dist_mag.init(num_pnts);
for ( i = 1 ; i < num_pnts-1 ; i++)
{
temp_dist1 = (float) (pnts(i) - pnts(i+1)).mag();
temp_dist2 = (float) (pnts(i-1) - pnts(i)).mag();
if ( temp_dist1 < temp_dist2)
dist_mag(i) = temp_dist1;
else
dist_mag(i) = temp_dist2;
}
temp_dist1 = (float) (pnts(1) - pnts(0)).mag();
temp_dist2 = (float) (pnts(num_pnts-2) - pnts(0)).mag();
if ( temp_dist1 < temp_dist2)
dist_mag(0) = temp_dist1;
else
dist_mag(0) = temp_dist2;
dist_mag(num_pnts-1) = dist_mag(0);
if (open_closed_flag == OPEN_CURVE)
{
tans(0) = pnts(1) - pnts(0);
tans(num_pnts-1) = pnts(num_pnts-1) - pnts(num_pnts-2);
}
else
{
tans(0) = pnts(1) - pnts(num_pnts-2);
tans(0).normalize();
tans(0) = tans(0) * dist_mag(0);
tans(num_pnts-1) = tans(0);
}
for ( i = 1 ; i < num_pnts-1 ; i++)
{
tans(i) = pnts(i+1) - pnts(i-1);
tans(i).normalize();
tans(i) = tans(i) * dist_mag(i);
}
for ( i = 0 ; i < num_pnts ; i++)
{
tans(i) = tans(i)*tan_k(i);
}
}
glm::vec2 start_tan(){
return(tans(0.0f));
}
void mesh::calculateTangents() {
std::vector<float> tans(3*vertCount, 0);
std::vector<float> bitans(3*vertCount, 0);
tangents.resize(4 * vertCount);
//calculate tentative tangents and bitangents for each triangle
for (int i = 0; i < triCount; i++) {
//find the vertices of the current triangle, and their UV coords
int vi1 = triangles[3*i];
int vi2 = triangles[3*i + 1];
int vi3 = triangles[3*i + 2];
glm::vec3 vert0(vertices[3*vi1], vertices[3*vi1 + 1], vertices[3*vi1 + 2]);
glm::vec3 vert1(vertices[3*vi2], vertices[3*vi2 + 1], vertices[3*vi2 + 2]);
glm::vec3 vert2(vertices[3*vi3], vertices[3*vi3 + 1], vertices[3*vi3 + 2]);
glm::vec2 uv0(texCoords[2*vi1], texCoords[2*vi1 + 1]);
glm::vec2 uv1(texCoords[2*vi2], texCoords[2*vi2 + 1]);
glm::vec2 uv2(texCoords[2*vi3], texCoords[2*vi3 + 1]);
//differences in position and UV coords
glm::vec3 dPos1 = vert1 - vert0;
glm::vec3 dPos2 = vert2 - vert0;
glm::vec2 dUV1 = uv1 - uv0;
glm::vec2 dUV2 = uv2 - uv0;
//calculate and store the tangent and bitangent
float coeff = 1.0f / (dUV1.x * dUV2.y - dUV1.y * dUV2.x);
glm::vec3 tan = dPos1 * dUV2.y - dPos2 * dUV1.y;
glm::vec3 bitan = dPos2 * dUV1.x - dPos1 * dUV2.x;
tan *= coeff;
bitan *= coeff;
tans[3*vi1] += tan.x;
tans[3*vi1 + 1] += tan.y;
tans[3*vi1 + 2] += tan.z;
tans[3*vi2] += tan.x;
tans[3*vi2 + 1] += tan.y;
tans[3*vi2 + 2] += tan.z;
tans[3*vi3] += tan.x;
tans[3*vi3 + 1] += tan.y;
tans[3*vi3 + 2] += tan.z;
bitans[3*vi1] += bitan.x;
bitans[3*vi1 + 1] += bitan.y;
bitans[3*vi1 + 2] += bitan.z;
bitans[3*vi2] += bitan.x;
bitans[3*vi2 + 1] += bitan.y;
bitans[3*vi2 + 2] += bitan.z;
bitans[3*vi3] += bitan.x;
bitans[3*vi3 + 1] += bitan.y;
bitans[3*vi3 + 2] += bitan.z;
}
//find the final tangent (and bitangent) for each vertex
for (int j = 0; j < vertCount; j++) {
glm::vec3 normal (normals[3*j], normals[3*j + 1], normals[3*j + 2]);
glm::vec3 tangent (tans[3*j], tans[3*j + 1], tans[3*j + 2]);
glm::vec3 bitangent (bitans[3*j], bitans[3*j + 1], bitans[3*j + 2]);
glm::normalize(tangent);
glm::normalize(bitangent);
//orthagonalize
glm::vec3 tangent_orth(normal);
tangent_orth *= glm::dot(normal, tangent);
tangent_orth = tangent - tangent_orth;
glm::normalize(tangent_orth);
//compute handedness
float handedness = 1.0f;
glm::vec3 nCrossT = glm::cross(normal, tangent_orth);
if(glm::dot(nCrossT, bitangent) > 0) {
handedness = 1.0f;
} else {
handedness = -1.0f;
}
//store the orthagonalized tangent and handedness
tangents[4*j] = tangent_orth.x;
tangents[4*j + 1] = tangent_orth.y;
tangents[4*j + 2] = tangent_orth.z;
tangents[4*j + 3] = handedness;
}
}
