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celestia/src/celengine/spheremesh.cpp

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// spheremesh.cpp
//
// Copyright (C) 2001-2009, the Celestia Development Team
// Original version by Chris Laurel <claurel@gmail.com>
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// IMPORTANT: This file is a relic from the early days of Celestia.
// It's sole function now is to handle the now-deprecated .cms mesh files;
// it will eventually be removed from Celestia.
#include <cmath>
#include <cstdint>
#include <cstring>
#include <utility>
#include <vector>
#include <celmodel/mesh.h>
#include "spheremesh.h"
SphereMesh::SphereMesh(float radius, int _nRings, int _nSlices)
{
createSphere(radius, _nRings, _nSlices);
}
SphereMesh::SphereMesh(const Eigen::Vector3f& size, int _nRings, int _nSlices)
{
createSphere(1.0f, _nRings, _nSlices);
scale(size);
}
SphereMesh::SphereMesh(const Eigen::Vector3f& size,
const DisplacementMap& dispmap,
float height)
{
createSphere(1.0f, dispmap.getHeight(), dispmap.getWidth());
scale(size);
displace(dispmap, height);
generateNormals();
fixNormals();
}
SphereMesh::SphereMesh(const Eigen::Vector3f& size,
int _nRings, int _nSlices,
DisplacementMapFunc func,
void* info)
{
createSphere(1.0f, _nRings, _nSlices);
scale(size);
displace(func, info);
generateNormals();
fixNormals();
}
SphereMesh::~SphereMesh()
{
delete[] vertices;
delete[] normals;
delete[] texCoords;
delete[] indices;
delete[] tangents;
}
void SphereMesh::createSphere(float radius, int _nRings, int _nSlices)
{
nRings = _nRings;
nSlices = _nSlices;
nVertices = nRings * (nSlices + 1);
vertices = new float[nVertices * 3];
normals = new float[nVertices * 3];
texCoords = new float[nVertices * 2];
nIndices = (nRings - 1) * (nSlices + 1) * 2;
indices = new unsigned short[nIndices];
tangents = new float[nVertices * 3];
int i;
for (i = 0; i < nRings; i++)
{
float phi = (static_cast<float>(i) / static_cast<float>(nRings - 1) - 0.5f) * static_cast<float>(PI);
for (int j = 0; j <= nSlices; j++)
{
float theta = static_cast<float>(j) / static_cast<float>(nSlices) * static_cast<float>(PI * 2.0);
int n = i * (nSlices + 1) + j;
auto x = std::cos(phi) * std::cos(theta);
auto y = std::sin(phi);
auto z = std::cos(phi) * std::sin(theta);
vertices[n * 3] = x * radius;
vertices[n * 3 + 1] = y * radius;
vertices[n * 3 + 2] = z * radius;
normals[n * 3] = x;
normals[n * 3 + 1] = y;
normals[n * 3 + 2] = z;
texCoords[n * 2] = 1.0f - static_cast<float>(j) / static_cast<float>(nSlices);
texCoords[n * 2 + 1] = 1.0f - static_cast<float>(i) / static_cast<float>(nRings - 1);
// Compute the tangent--required for bump mapping
auto tx = std::sin(phi) * std::sin(theta);
auto ty = -std::cos(phi);
auto tz = std::sin(phi) * std::cos(theta);
tangents[n * 3] = tx;
tangents[n * 3 + 1] = ty;
tangents[n * 3 + 2] = tz;
}
}
for (i = 0; i < nRings - 1; i++)
{
for (int j = 0; j <= nSlices; j++)
{
int n = i * (nSlices + 1) + j;
indices[n * 2 + 0] = i * (nSlices + 1) + j;
indices[n * 2 + 1] = (i + 1) * (nSlices + 1) + j;
}
}
}
// Generate vertex normals for a quad mesh by averaging face normals
void SphereMesh::generateNormals()
{
int nQuads = nSlices * (nRings - 1);
Eigen::Vector3f* faceNormals = new Eigen::Vector3f[nQuads];
int i;
// Compute face normals for the mesh
for (i = 0; i < nRings - 1; i++)
{
for (int j = 0; j < nSlices; j++)
{
float* p0 = vertices + (i * (nSlices + 1) + j) * 3;
float* p1 = vertices + ((i + 1) * (nSlices + 1) + j) * 3;
float* p2 = vertices + ((i + 1) * (nSlices + 1) + j + 1) * 3;
float* p3 = vertices + (i * (nSlices + 1) + j + 1) * 3;
// Compute the face normal. Watch out for degenerate (zero-length)
// edges. If there are two degenerate edges, the entire face must
// be degenerate and we'll handle that later
Eigen::Vector3f v0 = Eigen::Map<Eigen::Vector3f>(p1) - Eigen::Map<Eigen::Vector3f>(p0);
Eigen::Vector3f v1 = Eigen::Map<Eigen::Vector3f>(p2) - Eigen::Map<Eigen::Vector3f>(p1);
if (v0.norm() < 1e-6f)
{
v0 = Eigen::Map<Eigen::Vector3f>(p2) - Eigen::Map<Eigen::Vector3f>(p1);
v1 = Eigen::Map<Eigen::Vector3f>(p3) - Eigen::Map<Eigen::Vector3f>(p2);
}
else if (v1.norm() < 1e-6f)
{
v0 = Eigen::Map<Eigen::Vector3f>(p3) - Eigen::Map<Eigen::Vector3f>(p2);
v1 = Eigen::Map<Eigen::Vector3f>(p0) - Eigen::Map<Eigen::Vector3f>(p3);
}
Eigen::Vector3f faceNormal = v0.cross(v1);
float length = faceNormal.norm();
if (length != 0)
faceNormal *= (1 / length);
faceNormals[i * nSlices + j] = faceNormal;
}
}
auto* faceCounts = new int[nVertices];
for (i = 0; i < nVertices; i++)
{
faceCounts[i] = 0;
normals[i * 3] = 0;
normals[i * 3 + 1] = 0;
normals[i * 3 + 2] = 0;
}
for (i = 1; i < nRings - 1; i++)
{
for (int j = 0; j <= nSlices; j++)
{
int vertex = i * (nSlices + 1) + j;
faceCounts[vertex] = 4;
int face = (i - 1) * nSlices + j % nSlices;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
face = (i - 1) * nSlices + (j + nSlices - 1) % nSlices;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
face = i * nSlices + (j + nSlices - 1) % nSlices;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
face = i * nSlices + j % nSlices;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
}
}
// Compute normals at the poles
for (i = 0; i <= nSlices; i++)
{
int vertex = i;
int j;
faceCounts[vertex] = nSlices;
for (j = 0; j < nSlices; j++)
{
int face = j;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
}
vertex = (nRings - 1) * (nSlices + 1) + i;
faceCounts[vertex] = nSlices;
for (j = 0; j < nSlices; j++)
{
int face = nQuads - j - 1;
normals[vertex * 3] += faceNormals[face].x();
normals[vertex * 3 + 1] += faceNormals[face].y();
normals[vertex * 3 + 2] += faceNormals[face].z();
}
}
for (i = 0; i < nVertices; i++)
{
if (faceCounts[i] > 0)
{
float s = 1.0f / static_cast<float>(faceCounts[i]);
float nx = normals[i * 3] * s;
float ny = normals[i * 3 + 1] * s;
float nz = normals[i * 3 + 2] * s;
auto length = std::sqrt(nx * nx + ny * ny + nz * nz);
if (length > 0)
{
length = 1 / length;
normals[i * 3] = nx * length;
normals[i * 3 + 1] = ny * length;
normals[i * 3 + 2] = nz * length;
}
}
}
delete[] faceCounts;
delete[] faceNormals;
}
// Fix up the normals along the seam at longitude zero
void SphereMesh::fixNormals()
{
for (int i = 0; i < nRings; i++)
{
float* v0 = normals + (i * (nSlices + 1)) * 3;
float* v1 = normals + ((i + 1) * (nSlices + 1) - 1) * 3;
Eigen::Map<Eigen::Vector3f> n0(v0);
Eigen::Map<Eigen::Vector3f> n1(v1);
Eigen::Vector3f normal = n0 + n1;
normal.normalize();
v0[0] = normal.x();
v0[1] = normal.y();
v0[2] = normal.z();
v1[0] = normal.x();
v1[1] = normal.y();
v1[2] = normal.z();
}
}
void SphereMesh::scale(const Eigen::Vector3f& s)
{
int i;
for (i = 0; i < nVertices; i++)
{
vertices[i * 3] *= s.x();
vertices[i * 3 + 1] *= s.y();
vertices[i * 3 + 2] *= s.z();
}
// Modify the normals
if (normals != nullptr)
{
// TODO: Make a fast special case for uniform scale factors, where
// renormalization is not required.
Eigen::Vector3f is = s.cwiseInverse();
for (i = 0; i < nVertices; i++)
{
int n = i * 3;
Eigen::Vector3f normal = Eigen::Map<Eigen::Vector3f>(normals).cwiseProduct(is);
normal.normalize();
normals[n] = normal.x();
normals[n + 1] = normal.y();
normals[n + 2] = normal.z();
}
}
}
void SphereMesh::displace(const DisplacementMap& dispmap,
float height)
{
for (int i = 0; i < nRings; i++)
{
for (int j = 0; j <= nSlices; j++)
{
int n = (i * (nSlices + 1) + j) * 3;
Eigen::Map<Eigen::Vector3f> normal(normals);
int k = (j == nSlices) ? 0 : j;
Eigen::Vector3f v = normal * dispmap.getDisplacement(k, i) * height;
vertices[n] += v.x();
vertices[n + 1] += v.y();
vertices[n + 2] += v.z();
}
}
}
void SphereMesh::displace(DisplacementMapFunc func, void* info)
{
for (int i = 0; i < nRings; i++)
{
float v = (float) i / (float) (nRings - 1);
for (int j = 0; j <= nSlices; j++)
{
float u = (float) j / (float) nSlices;
int n = (i * (nSlices + 1) + j) * 3;
Eigen::Map<Eigen::Vector3f> normal(normals);
Eigen::Vector3f vert = normal * func(u, v, info);
vertices[n] += vert.x();
vertices[n + 1] += vert.y();
vertices[n + 2] += vert.z();
}
}
}
cmod::Mesh SphereMesh::convertToMesh() const
{
static_assert(sizeof(float) == sizeof(cmod::VWord), "Float size mismatch with vertex data word size");
constexpr std::uint32_t stride = 8;
std::vector<cmod::VertexAttribute> attributes{
cmod::VertexAttribute(cmod::VertexAttributeSemantic::Position,
cmod::VertexAttributeFormat::Float3,
0),
cmod::VertexAttribute(cmod::VertexAttributeSemantic::Normal,
cmod::VertexAttributeFormat::Float3,
3),
cmod::VertexAttribute(cmod::VertexAttributeSemantic::Texture0,
cmod::VertexAttributeFormat::Float2,
6),
};
cmod::Mesh mesh;
mesh.setVertexDescription(cmod::VertexDescription(std::move(attributes)));
// Copy the vertex data from the separate position, normal, and texture coordinate
// arrays into a single array.
std::vector<cmod::VWord> vertexData(stride * nVertices);
for (int i = 0; i < nVertices; i++)
{
cmod::VWord* vertex = vertexData.data() + stride * i;
std::memcpy(vertex, vertices + (i * 3), sizeof(float) * 3);
std::memcpy(vertex + 3, normals + (i * 3), sizeof(float) * 3);
std::memcpy(vertex + 6, texCoords + (i * 2), sizeof(float) * 2);
}
mesh.setVertices(nVertices, std::move(vertexData));
for (int i = 0; i < nRings - 1; i++)
{
std::vector<cmod::Index32> indexData;
indexData.reserve((nSlices + 1) * 2);
for (int j = 0; j <= nSlices; j++)
{
indexData.push_back(i * (nSlices + 1) + j);
indexData.push_back((i + 1) * (nSlices + 1) + j);
}
mesh.addGroup(cmod::PrimitiveGroupType::TriStrip, ~0u, std::move(indexData));
}
return mesh;
}
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