293 lines
6.2 KiB
C++
293 lines
6.2 KiB
C++
/*
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* Copyright (c) 2016-2019 Irlan Robson https://irlanrobson.github.io
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef SOFT_BODY_H
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#define SOFT_BODY_H
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#include <bounce/meshgen/sphere_mesh.h>
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struct b3QClothMesh : public b3ClothMesh
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{
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b3StackArray<b3Vec3, 256> clothVertices;
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b3StackArray<b3ClothMeshTriangle, 256> clothTriangles;
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b3ClothMeshMesh clothMesh;
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b3QClothMesh()
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{
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vertices = nullptr;
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vertexCount = 0;
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triangles = nullptr;
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triangleCount = 0;
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meshCount = 0;
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meshes = nullptr;
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sewingLineCount = 0;
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sewingLines = nullptr;
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}
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void SetAsSphere(float32 radius = 1.0f)
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{
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smMesh mesh;
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smCreateMesh(mesh, 2);
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clothVertices.Resize(mesh.vertexCount);
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for (u32 i = 0; i < mesh.vertexCount; ++i)
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{
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clothVertices[i] = radius * mesh.vertices[i];
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}
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clothTriangles.Resize(mesh.indexCount / 3);
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for (u32 i = 0; i < mesh.indexCount / 3; ++i)
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{
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clothTriangles[i].v1 = mesh.indices[3 * i + 0];
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clothTriangles[i].v2 = mesh.indices[3 * i + 1];
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clothTriangles[i].v3 = mesh.indices[3 * i + 2];
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}
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clothMesh.startTriangle = 0;
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clothMesh.triangleCount = clothTriangles.Count();
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clothMesh.startVertex = 0;
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clothMesh.vertexCount = clothVertices.Count();
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vertices = clothVertices.Begin();
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vertexCount = clothVertices.Count();
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triangles = clothTriangles.Begin();
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triangleCount = clothTriangles.Count();
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meshCount = 1;
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meshes = &clothMesh;
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}
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};
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class SoftBody : public Test
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{
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public:
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SoftBody()
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{
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m_mesh.SetAsSphere(2.0f);
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// Translate the cloth mesh upwards
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for (u32 i = 0; i < m_mesh.vertexCount; ++i)
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{
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m_mesh.vertices[i].y += 10.0f;
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}
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// Create cloth
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b3ClothDef def;
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def.mesh = &m_mesh;
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def.density = 0.2f;
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def.structural = 10000.0f;
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def.bending = 0.0f;
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def.damping = 0.0f;
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m_cloth = new b3Cloth(def);
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for (b3Particle* p = m_cloth->GetParticleList().m_head; p; p = p->GetNext())
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{
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p->SetRadius(0.05f);
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p->SetFriction(0.5f);
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}
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b3Vec3 gravity(0.0f, -9.8f, 0.0f);
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m_cloth->SetGravity(gravity);
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// Attach a world to the cloth
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m_cloth->SetWorld(&m_world);
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// Create static shapes
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{
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b3BodyDef bd;
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bd.type = e_staticBody;
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b3Body* b = m_world.CreateBody(bd);
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static b3BoxHull boxHull(10.0f, 1.0f, 10.0f);
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b3HullShape boxShape;
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boxShape.m_hull = &boxHull;
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b3ShapeDef sd;
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sd.shape = &boxShape;
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sd.friction = 0.5f;
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b->CreateShape(sd);
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}
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m_clothDragger = new b3ClothDragger(&m_ray, m_cloth);
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}
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~SoftBody()
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{
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delete m_clothDragger;
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delete m_cloth;
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}
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// Compute the volume of soft body
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float32 ComputeVolume() const
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{
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const b3ClothMesh* mesh = m_cloth->GetMesh();
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b3StackArray<b3Vec3, 256> positions;
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positions.Resize(mesh->vertexCount);
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for (u32 i = 0; i < mesh->vertexCount; ++i)
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{
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b3Particle* p = m_cloth->GetVertexParticle(i);
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positions[i] = p->GetPosition();
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}
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b3AABB3 aabb;
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aabb.Compute(positions.Begin(), positions.Count());
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return aabb.Volume();
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}
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// Apply pressure forces
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// Explanation available in the paper
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// "Pressure Model of Soft Body Simulation"
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void ApplyPressureForces()
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{
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const b3ClothMesh* mesh = m_cloth->GetMesh();
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// Volume in m^3
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float32 V = ComputeVolume();
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// Inverse volume
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float32 invV = V > 0.0f ? 1.0f / V : 0.0f;
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// Apply pressure forces on particles
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for (u32 i = 0; i < m_mesh.triangleCount; ++i)
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{
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u32 i1 = m_mesh.triangles[i].v1;
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u32 i2 = m_mesh.triangles[i].v2;
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u32 i3 = m_mesh.triangles[i].v3;
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b3Particle* p1 = m_cloth->GetVertexParticle(i1);
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b3Particle* p2 = m_cloth->GetVertexParticle(i2);
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b3Particle* p3 = m_cloth->GetVertexParticle(i3);
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b3Vec3 v1 = p1->GetPosition();
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b3Vec3 v2 = p2->GetPosition();
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b3Vec3 v3 = p3->GetPosition();
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b3Vec3 n = b3Cross(v2 - v1, v3 - v1);
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// Triangle area
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float32 A = n.Normalize();
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A *= 0.5f;
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// Ideal Gas Approximation
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// Number of gas moles
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const float32 k_n = 1.0f;
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// Ideal Gas Constant [J / K mol]
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const float32 k_R = 8.31f;
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// Gas temperature in Kelvin
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const float32 k_T = 100.0f;
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// Pressure in Pascals
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float32 P = invV * k_n * k_R * k_T;
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// Pressure vector
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b3Vec3 Pn = P * n;
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// Pressure force
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b3Vec3 FP = Pn * A;
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const float32 inv3 = 1.0f / 3.0f;
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b3Vec3 f = inv3 * FP;
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// Distribute
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p1->ApplyForce(f);
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p2->ApplyForce(f);
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p3->ApplyForce(f);
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}
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}
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void Step()
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{
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Test::Step();
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ApplyPressureForces();
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m_cloth->Step(g_testSettings->inv_hertz);
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m_cloth->Draw();
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if (m_clothDragger->IsDragging())
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{
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b3Vec3 pA = m_clothDragger->GetPointA();
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b3Vec3 pB = m_clothDragger->GetPointB();
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g_draw->DrawPoint(pA, 2.0f, b3Color_green);
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g_draw->DrawPoint(pB, 2.0f, b3Color_green);
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g_draw->DrawSegment(pA, pB, b3Color_white);
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}
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extern u32 b3_clothSolverIterations;
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g_draw->DrawString(b3Color_white, "Iterations = %d", b3_clothSolverIterations);
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float32 E = m_cloth->GetEnergy();
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g_draw->DrawString(b3Color_white, "E = %f", E);
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}
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void MouseMove(const b3Ray3& pw)
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{
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Test::MouseMove(pw);
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if (m_clothDragger->IsDragging() == true)
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{
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m_clothDragger->Drag();
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}
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}
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void MouseLeftDown(const b3Ray3& pw)
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{
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Test::MouseLeftDown(pw);
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if (m_clothDragger->IsDragging() == false)
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{
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m_clothDragger->StartDragging();
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}
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}
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void MouseLeftUp(const b3Ray3& pw)
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{
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Test::MouseLeftUp(pw);
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if (m_clothDragger->IsDragging() == true)
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{
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m_clothDragger->StopDragging();
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}
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}
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static Test* Create()
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{
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return new SoftBody();
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}
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b3QClothMesh m_mesh;
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b3Cloth* m_cloth;
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b3ClothDragger* m_clothDragger;
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};
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#endif |