readme

Algo de codigo de openGL que obtuve en la web :P

GL_shadow: an implementation of the stencil shadow volume technique
Copyright (C) 2005 Angelo "Encelo" Theodorou

Info
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Welcome to a little more complex demo, which required studying Blender Python OBJ importer, 
NeHe's lesson 27 and some other docs about shadow volume technique.
Actually the demo is a merge of an OBJ loader and some code for real-time shadow generation using 
the depth pass test (zpass).
If you are curious about testing the program with something heavier than a cube make it load 
suzanne.obj instead of cube.obj and you will admire the shadow projected by Suzanne, Blender's mascotte. :)
(On my card it scores near 1/5th of cube performance)

Compiling
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In order to compile use the included Makefile.
Should you have any problem with includes or libs, tweak it to suit your needs.

TODO and shortcomings of the current version
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- It would really like to actually implement Carmack's Reverse and volume capping, maybe in the future.
- Calculating the inverse matrix would make calculation of light position relative to object a lot easier.
- Shadow volume should be clipped to the view volume.
- Lights could be represented by a transparent textured quad or an object.
- Take in consideration object material properties.
- Update OBJ loader to the new (and I think more correct) Blender 2.40 importer script.

- Silhouette edge calculation is done twice even if it remains the same for both calls of ShadowVolume() inside 
CastShadow().
- I think there's an issue with normals and back facing polygons because, as you may easily notice, when a light 
is near a wall this become darker instead of brighter! :)

Notes
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- test_obj is a program made for testing OBJ loader routines, invoke it with an OBJ file as parameter.

- cube.mtl is filled with fake materials to show that the loader is actually capable of loading 
parameters from the right one.

- In this demo FrameTiming() and perspectiveGL() were moved in extra.c, leaving to main.c only 
the main() function.

- I have added code for window resizing based on SDL events and OpenGL frustum and viewport recalibration.

- The prgram stops when the window loses input focus or is iconified.
  Strangely SDL_APPINPUTFOCUS event is thrown even when the application regain only mouse focus.

- Projecting the shadow volume to infinity is achieved setting the w component of the 
  projected points of the volume to 0.
  Take a look to shadow.c comments.