remove some un-used data from b3Generic6DofConstraint

add GLRenderToTexture helper class
enable OpenGLTrueTypeFont test

btgui/OpenGLWindow/GLRenderToTexture.cpp

@@ -0,0 +1,78 @@
+
+///See http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/
+
+#include "GLRenderToTexture.h"
+
+GLRenderToTexture::GLRenderToTexture()
+:m_framebufferName(0)
+{
+}
+	
+void GLRenderToTexture::init(int width, int height)
+{
+	glGenFramebuffers(1, &m_framebufferName);
+	glBindFramebuffer(GL_FRAMEBUFFER, m_framebufferName);
+	
+	GLuint m_renderedTexture;
+	glGenTextures(1, &m_renderedTexture);
+
+	// "Bind" the newly created texture : all future texture functions will modify this texture
+	glBindTexture(GL_TEXTURE_2D, m_renderedTexture);
+
+	// Give an empty image to OpenGL ( the last "0" )
+	glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, width, height, 0,GL_RGB, GL_UNSIGNED_BYTE, 0);
+
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+
+
+	// The depth buffer
+	glGenRenderbuffers(1, &m_depthrenderbuffer);
+	glBindRenderbuffer(GL_RENDERBUFFER, m_depthrenderbuffer);
+	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
+	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, m_depthrenderbuffer);
+
+	glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, m_renderedTexture, 0);
+
+}
+
+bool GLRenderToTexture::enable()
+{
+	bool status = false;
+
+		// Set the list of draw buffers.
+	GLenum drawBuffers[2] = {GL_COLOR_ATTACHMENT0,0};
+	glDrawBuffers(1, drawBuffers);
+
+	// Always check that our framebuffer is ok
+	if(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE)
+	{
+		status = true;
+	}
+
+	return status;
+
+}
+
+void GLRenderToTexture::disable()
+{
+	glBindFramebuffer( GL_FRAMEBUFFER, 0 );
+	glBindTexture(GL_TEXTURE_2D, 0);
+}
+	
+GLRenderToTexture::~GLRenderToTexture()
+{
+	glBindFramebuffer( GL_FRAMEBUFFER, 0 );
+
+	if (m_depthrenderbuffer)
+		glDeleteRenderbuffers(1,&m_depthrenderbuffer);
+
+	if(m_renderedTexture) 
+		glDeleteTextures(1, &m_renderedTexture);
+
+	if( m_framebufferName)
+	{ 
+		glDeleteFramebuffers(1, &m_framebufferName);
+	}
+}
+