gcad-GL

• is a hi-level library connecting CAD-applications with OpenGL
• written in C, under Gpl3 license.
• create objects by calling C-functions
• with attributes for each individual object:

persistance-attributes (permanent or temporay)
grafic-attributes (color or line thickness or line-stipple)
and operational-attributes (normal or hilited or dimmed);

OBJECTS:

• points,polygons
• surface-triangles triangles, fan, stripe
• surface-indexed indexed triangles, normals
• surface-textured triangle-mesh, image
• symbols-2D eg 2D-Text, dimensions, tag, balloon ..
  always normal to eyevector, rotated
• symbols-3D eg vectors, arrow(head)s, axis, ..

ATTRIBUTES:

persistance-attribute:

• permanent - objects have DL-record
• dynamic - have no DL-record, unlimited nr,
  exist only until creation of next permanent object
• temporary - have no DL-record, limited nr, can be created, remove individually

grafic-attributes:

• surfaces: ColRGB - color,texture,transparency;
  style (shaded | symbolic)
• point,curves: Att_ln - color,thickness,stipple

grafic-attributes are stored in the DL,
can be modified for individual objects,
next redraw updates this objects

operational-attributes (only for permanent-objects):

• normal | hilite | dimmed | hidden
• operational-attributes are stored in the DL
• can be modified for individual objects,
  next redraw updates this objects

Modules of gcad-GL:

  GUI    user interface independent from drivers (Gtk, OpenGL)
         callbacks from mouse, keys, ..
    Gtk    menus, OpenGL-binding
    
  GR     grafic-functions independent from drivers (Gtk, OpenGL)
    GL     OpenGL V3.3 or V1
    
  DL     DisplayList (control of grafical attributes)

SHADERS:

• shadSUn vertices
  triangles (triangles, triangle-loops, triangle-fans)

• shadSUi vertices + normals + indices
  surfaces with boundaries

• shadSUt vertices + texture-uv + indices (textured quads)
  surfaces with texture

• shadCV vertices only
  points, curves

• shadSY2 vertices (3D WCS)
  2D-symbols (points, polygons, rotated)
  text, dimensions, ballons, leaderlines, ..
  tags - colored 2D-rectangles [with text]
  images

• shadSY3 vertices (3D WCS)
  3D-symbols (text, plane, axis, arrow[head], ..)

EXAMPLE:

	int GUI_CB_win_is_up () {
	  // window has started; display a triangle
	  GR_perm_sur (..);
	  // redraw all active objects
	  GR_redraw ();
	  return 0;
	}

	int GUI_CB_key (int iKey) {
	  // callback - user has pressed a key
	  if(iKey == GUI_KeyEsc) exit (0);
	  if(iKey == 't') {
	    // add permanent surface ..
	    GR_perm_sur (..);
	    GR_redraw ();
	  }
	  return 0;
	}

Full code see app.c

Build:

Prerequisites:
gcc with tools (ctags)

On debian-OS:
sudo apt install libgtk-3-dev mesa-common-dev

On redhat-OS:
sudo yum install gtk3-devel mesa-libGL-devel

• in console goto directory ~/gcad-GL/app/
• build list-tool ../bin/GUI_dlg1_gtk3 with:
  ./GUI_dlg1.sh
• build and execute demoprogram a.out with:
  make && ./a.out
  For using see Help-file using.txt and console-output

TODO: (not yet implemented, help wanted)

• shaded_faces - geometry-shader ?
  get angle normal-eyeVector = shading-factor
• selection of objects
• select-box (display box, select all objects in box)
• line-stipple (dashed, dashed-long, dash-dot)
• tesselate with shader (may not modify boundary - to be tested)
• perspectivic projection
• make shared overlay (libgcad-GL-gtk3-gl3.so)

Already working:

• orthographic projection with zoom, pan, rotate
• create points, curves, triangles, vectors, 2D-buttons
• change colors, width of curves, points
• hide / redisplay objects

Opengl-legacy-testprograms

In directory tests_gl_legacy are several minimum-code-programs for
checking legacy-Opengl with Gtk.
nvidia-driver-495 with Gtk2 works OK;
nvidia-driver-495 with Gtk3 cannot get the Z-buffer (only 2D works).
Gtk3 with openglarea does not support legacy-Opengl.
Compile / Link programs with eg -
make -f gtk3_glx.mak
Run programs with eg -
./gtk3_glx

glx_only	GLX -	OK
gtk2_glx	Gtk2 GLX	OK (also OK with driver nvidia-driver-495)
gtk3_glx	Gtk3 GLX	only 2D (no Z-buffer) with nvidia-driver-495
		OK with driver readeon
		OK with driver nouveau (NV137)
gtk3_gla	Gtk3 openglarea	does not provide Legacy-OpenGL-window

History:

2022-01-24 V-0.06 Update Makefile. 2021-12-23 V-0.05 legacy-Opengl-testprogs added
2021-11-26 V-0.04 vectors - true-length, normalized
2021-10-11 dynamic-symbols, directory-structure, cursors, blocking ..
2021-09-10 First release.

Report bugs, improvements to support at gcad3d.org

// EOF