Dolfyn: G95 and F03GL

1. Introduction

Stuff needed:

g95: www.g95.org
f03gl: www-stone.ch.cam.ac.uk/pub/f03gl

Install g95 and build f03gl on a GNU/Linux system. The programms presented here were created, compiled and run on openSuSE 10.3 and Debian etch systems. They have not been tested on other platforms. Note that the OpenGL (or Mesa) development libraries (incl. GLUT) have to be installed prior to compiling f03gl and the examples.

More Fortran OpenGL information can be found at math.nist.gov/f90gl. In the examples symbolic links have been made to:

GLUT_fonts.o (needed for bitfonts).
opengl_gl.mod (GL module name is in lower case)
OpenGL_gl.o
opengl_glu.mod (GLu module name is in lower case)
OpenGL_glu.o
opengl_glut.mod (GLut module name is in lower case)
OpenGL_glut.o

A typical compilation command could be
$ g95 -o binary source.f90 \
OpenGL_glut.o OpenGL_glu.o OpenGL_gl.o -L/usr/lib -lglut -lGL -lGLU

G95 already incorporates many Fortran2003 features. Some are needed for f03gl:

Value type declaration value.
The BIND(C) construct.
ISO_C_BINDING.
ENUMERATION support.
Fortran 2003 BOZ in INT, REAL etc.
Stream I/O has been used for reading in the textures (see below).
Note that character strings need to be terminated with char(0) when passed on to a C function.

Note that OpenGL relies on constants (Fortran does not know about the concept of unsigned variables, so they have to be casted to the base form and converted by hand):

GL type	F95/F03 type	kind	value	C type
GLbyte	C_SIGNED_CHAR	integer	1	signed char
GLshort	C_SHORT	integer	2	short
GLint	C_INT	integer	4	int
GLsizei	C_INT	integer	4	int
GLboolean	C_SIGNED_CHAR	integer	1	unsigned char
GLenum	C_INT	integer	4	unsigned int
GLbitfield	C_INT	integer	4	unsigned int
GLcint	C_INT	integer	4	signed char
GLubyte	C_SIGNED_CHAR	integer	1	unsigned char
GLushort	C_SHORT	integer	2	unsigned short
GLuint	C_INT	integer	4	unsigned int
GLfloat	C_FLOAT	real	4	float
GLdouble	C_DOUBLE	real	8	double
GLclampf	C_FLOAT	real	4	float
GLclampd	C_DOUBLE	real	8	double

Finally some very important ISO_C_BINDING constants:

C_NULL_CHAR for the C null character '\0' (or char(0)).
C_PTR is interoperable with any C data pointer type.
C_NULL_PTR is of type C_PTR; it has the value of a C null data pointer.
C_FUNPTR is interoperable with any C function pointer type.
C_NULL_FUNPTR is of type C_FUNPTR; it has the value of a C null function pointer.
C_F_POINTER(CPTR, FPTR [,SHAPE]), associates a data pointer with the target of a C pointer and specifies its shape.
C_FUNLOC(X), returns the C address of a function pointer.
C_LOC(X), returns the C address of the argument.

Step by step instructions:

Create a directory (eg. 'tmpdir').
Download the files and save them in there:
- f03gl.tgz
- cc.tgz
- rb.tgz
- sb.tgz
'cd' into the directory and unpack the tar-balls:
- tar xvzof f03gl.tgz
- tar xvzof cc.tgz
- tar xvzof rb.tgz
- tar xvzof sb.tgz
'cd' into the f03gl directory and hit 'make'.
'cd' into the other directories and hit 'make'.

2. NIST f90gl

Modifications of the original tarball and the NIST examples are available here. f90gl

	trivial. Simple white square. Glutinit call simplified to call glutinit().
	blender. Antialiased text.
	checker. Location of image changed to c_loc(checkImage).
	fscene. Minor changes.
	glutdino (same result as gltdino2). Alter tobj definition to: type(c_ptr) :: tobj and the calls to the C functions ... call glutesscallback(tobj, GLU_TESS_BEGIN, & c_funloc(glbegin)) call glutesscallback(tobj, GLU_TESS_VERTEX, & c_funloc(glvertex2fv)) call glutesscallback(tobj, GLU_TESS_END, & c_funloc(glend)) ... and the call to the data into: call glutessvertex(tobj, vertex, & c_loc(data(i)%val))
	logo. Set target for: real(GLfloat), dimension(90), target :: cva(3,30000) and then ... call glNormalPointer(GL_FLOAT,12,c_loc(cva(1,n0))) call glVertexPointer(3,GL_FLOAT,12, & c_loc(cva(1,n0+1)) ) ... Next glIsList returns an integer... so ... if(glIsList(thelist)==1) & call gldeletelists(thelist,1_glsizei) ...
	modview. Add //char(0) and create the menu with: ... button_left = glutCreateMenu(set_left_button) call glutAddMenuEntry('rotate'//char(0),ROTATE) call glutAddMenuEntry('zoom'//char(0),ZOOM) ...
	molehill. Change the declaration of nurb into type(c_ptr) :: nurb
	olympic (same result as olympic3). Mismatch of interface for Key: subroutine Key(%VAL(ikey), %VAL(x), %VAL(y)) use olympic_mod integer(GLubyte), intent(inout):: ikey integer(glInt), intent(inout):: x, y end subroutine key Finally ikey is GLubyte and not glInt.
	scube.
	sphere.
	stars.
	torus. Glutinit call simplified to call glutinit().
	fbitfont.
	eps. In select constructs as in: case (int(GL_PASS_THROUGH_TOKEN)) the GL_PASS_THROUGH_TOKEN should be an integer... and not a real. In OpenGL_gl.f90 however they were defined as floats. Finally glIsList returns an integer.
	array. Introduce type(c_ptr), pointer :: cstr and change the pointer to the string into: cstr=glGetString(GL_VENDOR) call c_f_pointer(cptr=cstr, fptr=str)
	polyoff. Glutinit call simplified to call glutinit().
	plotfunc. Avoided name overlap for "menu_handler".

3. OpenGL Green Book

The next examples are based on Computer Graphics with OpenGL. GreenBook

This new edition is a complete revision, bringing the text up to date with current advances in computer graphics technology and applications. Assuming readers have no prior familiarity with computer graphics, the authors' both authorities in their field's present basic principles for design, use, and understanding of computer graphics systems using their well-known, and accessible writing style. It includes an exploration of GL, PHIGS, PHIGS+, GKS and other graphics libraries and covers topics such as distributed ray tracing, radiosity, physically based modeling, particle systems, and visualization techniques. For professionals in any area of computer graphics: CAD, Animation, Software Design, etc.

The g95 files are available here.

	fgl01. Open a window and draw a red line. ... call glClear(GL_COLOR_BUFFER_BIT) call glColor3f(1.0,0.0,0.0) call glBegin(GL_LINES) call glVertex2i(180,20) call glVertex2i( 20,80) call glEnd() ...
	fgl03. Using display lists. ... integer(kind=GLuint) :: Hexagon ... Hexagon = glGenLists(1) call glNewList( Hexagon, GL_COMPILE) call glColor3f( 1.0, 0.0, 0.0 ) call glBegin(GL_POLYGON) do i=1,7 ... call glVertex2i( ix, iy) end do call glEnd call glEndList ...
	fgl04. A bar chart with characters. ... call glColor3f(0.0,0.0,0.0) xRaster = 20 do i=1,12 call glRasterPos2i(xraster,yraster) do j=3(i-1)+1,3(i-1)+3 call glutBitmapCharacter( & GLUT_BITMAP_HELVETICA_12, & iachar(label(j))) end do xraster=xraster+50 end do ...
	fgl05. Three dimensional viewing example. ... call glColor3f(0.0,1.0,0.0) call glPolygonMode(GL_FRONT,GL_FILL) call glPolygonMode(GL_BACK,GL_LINE) call glBegin(GL_QUADS) call glVertex3f( 0.0, 0.0, 0.0) call glVertex3f(100.0, 0.0, 0.0) call glVertex3f(100.0, 100.0, 0.0) call glVertex3f( 0.0, 100.0, 0.0) call glEnd ...
	fgl06. A perspective view of the five GLUT polyhedra, scaled and positioned within the display window. ... call glutWirecube(1.0_gldouble) ... call glutWireDodecahedron() ... call glutWireTetrahedron() ... call glutWireOctahedron() ... call glutWireIcosahedron() ...
	fgl07. Display of the GLUT sphere, GLUT cone and GLUT cylinder (using quadrics). ... type(c_ptr) :: ptr = c_null_ptr ... ptr = gluNewQuadric() call gluQuadricDrawStyle(ptr,GLU_LINE) call gluCylinder(ptr,s1,s2,s3,6,4) ...
	fgl08. Mouse droppings. subroutine mouse(ibutton,iaction,ix,iy) ... integer(GLint), intent(in), value :: & ibutton, iaction, ix, iy ... if( ibutton == GLUT_LEFT_BUTTON .and. & iaction == GLUT_DOWN )then call plotpoint(ix,winHeight-iy) call glFlush() endif ...
	fgl09. Example of an interactive mouse procedure. subroutine drawline(p1,p2) ... type(Point), intent(in) :: p1, p2 ... call glBegin(GL_LINES) call glVertex2i(p1%x,p1%y) call glVertex2i(p2%x,p2%y) call glEnd() ...

4. OpenGL Red Book

These examples are based on the Red Book. RedBook

The OpenGL Programming Guide, Fifth Edition, provides definitive and comprehensive information on OpenGL and the OpenGL Utility Library. This fifth edition of the 'red book' describes the latest features of OpenGL Versions 1.5 and 2.0, including the introduction of the OpenGL Shading Language. You will find clear explanations of OpenGL functionality and many basic computer graphics techniques, such as building and rendering 3D models; interactively viewing objects from different perspective points; and using shading, lighting, and texturing effects for greater realism. In addition, this book provides in-depth coverage of advanced techniques, including texture mapping, antialiasing, fog and atmospheric effects, NURBS, image processing, and more.

The g95 files are available here.

	fgl10. Wide stippled lines (fig. 2-9). ... call glLineWidth(5.0) ! dotted call glLineStipple(1,z'0101'_Glushort) call drawline( 50.,100.,150.,100.) ! dashed call glLineStipple(1,z'00FF'_Glushort) call drawline(150.,100.,250.,100.) ! dash dot dash call glLineStipple(1,z'1C47'_Glushort) call drawline(250.,100.,350.,100.) ...
	fgl11. Polygon stipple patterns (fig. 2-11). ... call glenable(GL_POLYGON_STIPPLE) call glpolygonstipple(fly) call glrectf(125.0,25.0,225.,125.) call glpolygonstipple(halftone) call glrectf(225.0,25.0,325.,125.) call gldisable(GL_POLYGON_STIPPLE) ...
	fgl12. Transformed cube (fig. 3-3)
	fgl13. Clipped wireframe sphere (fig. 3-23). ... ! clip lower half call glClipPlane(GL_CLIP_PLANE0, eqn1) call glEnable(GL_CLIP_PLANE0) ! clip left half call glClipPlane(GL_CLIP_PLANE1, eqn2) call glEnable(GL_CLIP_PLANE1) call glRotatef(90.0, 1.0, 0.0, 0.0) call glutWireSphere(radius, 20,16) ...
	fgl14. Planetary system. ... ! zon call glutWireSphere(radzon,20,16) ! planeet call glRotatef(Year, 0.0,1.0,0.0) call glTranslatef(2.8,0.0,0.0) call axis(0.4) call glRotatef(Day, 0.0,1.0,0.0) call glColor3f(1.0,1.0,1.0) call glPushMatrix() call glRotatef(20.0, 0.0,0.0,1.0) call glutWireSphere(radplan,10,8) call glPopMatrix() ...
	fgl15. Plate 11. A smooth shaded triangle. ... call glBegin(GL_TRIANGLES) call glColor3f(1.0,0.0,0.0) call glVertex2f(5.0,5.0) call glColor3f(0.0,1.0,0.0) call glVertex2f(25.0,5.0) call glColor3f(0.0,0.0,1.0) call glVertex2f(5.0,25.0) call glEnd ...
	fgl16. A lit sphere. ... call glShadeModel(GL_SMOOTH) call glMaterialfv(GL_FRONT, GL_SPECULAR, spec) call glMaterialfv(GL_FRONT, GL_SHININESS, shine) call glLightfv(GL_LIGHT0, GL_POSITION, pos) call glLightfv(GL_LIGHT0, GL_DIFFUSE, white) call glLightfv(GL_LIGHT0, GL_SPECULAR, white) call glLightModelfv(GL_LIGHT_MODEL_AMBIENT, amb) call glEnable(GL_LIGHTING) call glEnable(GL_LIGHT0) call glEnable(GL_DEPTH_TEST) ... call glutSolidSphere(radius,32,32) ...
	fgl17. Triangle selection example. Depth values (which are in the range [0,1]) are multiplied by 2^32 - 1, before being placed in the hit record as an unsigned integer. So this needs to be converted into something usable: double precision function & convert_uint_to_double( uint ) ... ! check highest bit if( btest(uint,31) )then big = 4294967295.0 else big = 0.0 endif ! clear highest bit iconv = ibclr(uint,31) ! simple type conversion: convert_uint_to_double = dble(iconv) + big end function convert_uint_to_double
	fgl18. Clicking. Relates to fgl17. ... hits = glRendermode(GL_RENDER) call processhits(hits, selectBuf) call glutPostRedisplay ...
	fgl19. Shows the use of 'PassThrough tokens'. ... if( mode == GL_FEEDBACK ) call glPassThrough(2.0) call glBegin(GL_POINTS) call glNormal3f( 0.0, 0.0, 1.0) call glVertex3f( 50.0, 50.0, 0.0) call glEnd ...
	fgl20.
	fgl21.

5. OpenGL Blue Book

The next examples are based on the Blue Book. BlueBook

OpenGL SuperBible, Fourth Edition, begins by illuminating the core techniques of 'classic' OpenGL graphics programming, from drawing in space to geometric transformations, from lighting to texture mapping. The authors cover newer OpenGL capabilities, including OpenGL 2.1's powerful programmable pipeline, vertex and fragment shaders, and advanced buffers. They also present thorough, up-to-date introductions to OpenGL implementations on multiple platforms, including Windows, Mac OS X, GNU/Linux, UNIX, and embedded systems. The reference pages for all of the OpenGL 2.1 commands are included!

These examples rely on textures. The function interface is:
interface
  function fgltLoadTGA(FileName,width,height,components,eform,image)
    use, intrinsic :: iso_c_binding
    type(c_ptr), target :: fgltloadTGA
    character, dimension(*), intent(IN) :: FileName
    integer(c_int), intent(out) :: width, height
    integer(c_int), intent(out) :: components, eform
    integer(c_char), dimension(:), allocatable, &
        intent(out), target :: image
  end function
end interface

The g95 files are available here.

	block. Display changes everytime the spacebar is hit.
	pointsz. Loop around in a circle three times. Set the point size and draw the point. ... ! Specify the point size call glPointSize(curSize) ! Draw the point call glBegin(GL_POINTS) call glVertex3f(x, y, z) call glEnd ...
	triangle. Explores depths and culling. ... ! Create the Menu im = glutCreateMenu(ProcessMenu) call glutAddMenuEntry & ('Toggle depth test'//char(0),1) call glutAddMenuEntry & ('Toggle cull backface'//char(0),2) call glutAddMenuEntry & ('Toggle outline back'//char(0),3) call glutAttachMenu(GLUT_RIGHT_BUTTON) ...
	pstipple. ... ! Black background call glClearColor(0.0, 0.0, 0.0, 1.0 ) ! Set drawing color to red call glColor3f(1.0, 0.0, 0.0) ! Enable polygon stippling call glEnable(GL_POLYGON_STIPPLE) ! Specify a specific stipple pattern call glPolygonStipple(fire) ...
	scissor.
	stencil. ... ! Now draw except where the stencil pattern is 0x1 ! dont make any further changes to the stencil buffer call glStencilFunc(GL_NOTEQUAL, z'01', z'01') call glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP) ! Now draw red bouncing square ! (x and y) are modified by a timer function call glColor3f(1.0, 0.0, 0.0) call glRectf(x, y, x + rsize, y - rsize) ...
	solar. ... ! Move the light after we draw the sun! call glLightfv(GL_LIGHT0,GL_POSITION,lightPos) ! Rotate coordinate system call glRotatef(fEarthRot, 0.0, 1.0, 0.0) ! Draw the Earth call glColor3f(0.0,0.0,1.0) call glTranslatef(105.0,0.0,0.0) call glutSolidSphere(dble(15.), 30, 17) ...
	transform.
	transformgl.
	sphereworld1. Introduces OOP-style GLframes class: ... ! Default. At the origin, looking ! down the positive Z axis. type :: GLFrame sequence real,dimension(3) :: Org = (/0.0,0.0, 0.0/) real,dimension(3) :: Up = (/0.0,1.0, 0.0/) real,dimension(3) :: Frw = (/0.0,0.0,-1.0/) end type GLFrame ...
	ambient.
	litjet.
	shinyjet.
	spot.
	shadow.
	sphereworld2.
	reflection.
	smoother.
	sphereworld3.
	fogged.
	motionblur.
	pyramid.
	sphereworld4.
	tunnel.
	toon.
	texgen.
	cubemap.
	snowman.
	bezier.
	bez3d.
	bezlit.
	nurbs.
	nurbt.
	florida. The polygon tesselation fails! This is the only case of this large set which failed.
	sphereworld5.
	starrynight.
	cubedx.
	thunderbird.
	thunderbirdgl. Introduces OOP-style CTriangleMeshes: ... type :: CTriangleMesh integer(GLuint), dimension(:), allocatable :: Indexes real(GLfloat), dimension(:), allocatable :: Verts real(GLfloat), dimension(:), allocatable :: Norms real(GLfloat), dimension(:), allocatable :: TexCoords integer(GLint) :: nMaxIndexes = 0 integer(GLint) :: nNumIndexes = 0 integer(GLint) :: nNumVerts = 0 end type CTriangleMesh ...
	thunderbirdvbo. Same idea but now with Vertex Buffer Objects: ... ! Texture coordinates call glBindBuffer(GL_ARRAY_BUFFER, & self%bufferObjects(TEXTURE_DATA)) call glTexCoordPointer(2, GL_FLOAT, 0, c_null_ptr) ! Indexes call glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, & self%bufferObjects(INDEX_DATA)) call glDrawElements(GL_TRIANGLES, self%nNumIndexes, & GL_UNSIGNED_INT, c_null_ptr) ...
	planets.
	moons.
	planets2.
	oocquery. Chapter 13, demonstrates occlusion queries. ... if( occlusionDetection == GL_TRUE )then ! Check if this sphere would be occluded call glGetQueryObjectiv(queryIDs(i),& GL_QUERY_RESULT, passingSamples(i)) if( passingSamples(i) == 0 ) occluded = GL_TRUE endif ...
	shadowmap.

6. Warning

You need to know what to do. The codes and files are 'as is'. The software and files are there to give you an impression only without any guarantee whatsoever.

Enjoy g95 and f03gl!


	Franken Consultancy