add ImplicitCloth demo, by Stan Melax

add SimpleOpenGL3App, used in ImplicitCloth demo. The Bullet 3.x demos should use this as a template, it will clean up some of the mess.

Demos3/ImplicitCloth/main.cpp

@@ -0,0 +1,83 @@
+#include "stan/vecmath.h"
+#include "stan/Cloth.h"
+#include "Bullet3Common/b3Vector3.h"
+#include "../../btgui/OpenGLWindow/SimpleOpenGL3App.h"
+
+Cloth* cloth = 0;
+
+int numX = 60, numY=60;
+const size_t total_points = (numX)*(numY);
+
+void drawCloth(class GLInstancingRenderer* renderer)
+{
+	GLint err = glGetError();
+    assert(err==GL_NO_ERROR);
+	
+	
+	err = glGetError();
+    assert(err==GL_NO_ERROR);
+	
+	b3AlignedObjectArray<unsigned int> indices;
+
+	for (int i=0;i<cloth->springs.count;i++)
+	{
+		indices.push_back(cloth->springs[i].a);
+		indices.push_back(cloth->springs[i].b);
+	}
+	float lineColor[4]={0.4,0.4,1.0,1};
+	renderer->drawLines(&cloth->X[0].x,lineColor,total_points,sizeof(float3),&indices[0],indices.size(),1);
+	err = glGetError();
+    assert(err==GL_NO_ERROR);
+	float pointColor[4]={1,0.4,0.4,1};
+	renderer->drawPoints(&cloth->X[0].x,pointColor,total_points,sizeof(float3),6);
+	err = glGetError();
+    assert(err==GL_NO_ERROR);
+	
+	
+}
+
+int main(int argc, char* argv[])
+{
+	float size=10;
+	cloth = ClothCreate(numX,numY,size);
+	
+	float dt = 1./120.f;
+	
+	SimpleOpenGL3App* app = new SimpleOpenGL3App("title",1024,768);
+	app->m_instancingRenderer->setCameraDistance(13);
+	app->m_instancingRenderer->setCameraPitch(0);
+	app->m_instancingRenderer->setCameraTargetPosition(b3MakeVector3(0,0,0));
+
+	GLint err = glGetError();
+    assert(err==GL_NO_ERROR);
+	
+	do
+	{
+		GLint err = glGetError();
+		assert(err==GL_NO_ERROR);
+		app->m_instancingRenderer->init();
+		app->m_instancingRenderer->updateCamera();
+		
+		app->drawGrid();
+		app->drawText("Cloth simulation using implicit integration, by Stan Melax",10,10);
+		cloth->Simulate(dt);
+		cloth->cloth_gravity.y = -9.8;//-9.8;//-9.8;//-9.8;//0;//-9.8;//0;//-9.8;//0;//-9.8;
+		cloth->cloth_gravity.z =-9.8;//0;//-9.8;//0;//-9.8;
+
+		cloth->spring_struct=10000000.0f;
+		cloth->spring_shear=10000000.0f;
+
+		//cloth->spring_struct=1000000.0f;
+		//cloth->spring_shear=1000000.0f;
+
+		cloth->spring_damp = 0;//100;
+
+		drawCloth(app->m_instancingRenderer);
+
+		app->swapBuffer();
+	} while (!app->m_window->requestedExit());
+
+	delete cloth;
+	delete app;
+	return 0;
+}