20 replies to this topic

[Vifani]

Hi guys,

someone have some ideas about how realize a per pixel lighting model in OpenGL without using nVidia register combiners ?

[anubis]

if you don't want to use register combiners you're not in for fragment programs as well, right ? but first of all... why do you need to do this ?

[Vifani]

I have an ATi Radeon 9800 Pro graphic card so I can't use nVidia Registers Combiner.

I want to realize a good lighting system for my game engine and I have decided to use a per pixel lighting instead of per vertex light and lightmap that I think are obsolete.

[Dia]

Well, you don't have to use the nVidia register combiners. You can simply use normal vertex and fragment shaders.

If you are implementing Phong lighting, check this link.

Hope it helps.

[anubis]

i have several fragment shader implementations ready for different lighting models. i was going to use them in my demo, which i won't be able to complete. so if you want to see them feel free to contact me...

[davepermen]

just run ARB_fragment_program. its great, and on all new radeons and gfFX cards supported.

[anubis]

even on gf4 i think

[davepermen]

no. gf4 cannot run it.

reason one: it does not have floatingpoint but only 9bit fixedpoint math (or 10bit)
reason two: it cannot excecute that much instructions
reason three: it cannot do programable texture fetches, only confiruable predefined settings, and thats it

but the main reason: its no dx9 card. because ARB_fragment_program == ps2.0

[anubis]

oi mate, my per pixel lighting code just ran on a gf4 using the ARB_fragment_program extension. i saw it and for once i believe my eyes

[baldurk]

from my glxinfo output:

OpenGL renderer string: GeForce4 Ti 4600/AGP/SSE/3DNOW!
OpenGL version string: 1.4.0 NVIDIA 43.49
OpenGL extensions:
  GL_ARB_depth_texture, GL_ARB_imaging, GL_ARB_multisample, 
  GL_ARB_multitexture, GL_ARB_point_parameters, GL_ARB_shadow, 
  GL_ARB_texture_border_clamp, GL_ARB_texture_compression, 
  GL_ARB_texture_cube_map, GL_ARB_texture_env_add, 
  GL_ARB_texture_env_combine, GL_ARB_texture_env_dot3, 
  GL_ARB_texture_mirrored_repeat, GL_ARB_transpose_matrix, 
  GL_ARB_vertex_buffer_object, GL_ARB_vertex_program, GL_ARB_window_pos, 
  GL_S3_s3tc, GL_EXT_abgr, GL_EXT_bgra, GL_EXT_blend_color, 
  GL_EXT_blend_minmax, GL_EXT_blend_subtract, GL_EXT_compiled_vertex_array, 
  GL_EXT_draw_range_elements, GL_EXT_fog_coord, GL_EXT_multi_draw_arrays, 
  GL_EXT_packed_pixels, GL_EXT_paletted_texture, GL_EXT_point_parameters, 
  GL_EXT_rescale_normal, GL_EXT_secondary_color, 
  GL_EXT_separate_specular_color, GL_EXT_shadow_funcs, 
  GL_EXT_shared_texture_palette, GL_EXT_stencil_wrap, GL_EXT_texture3D, 
  GL_EXT_texture_compression_s3tc, GL_EXT_texture_cube_map, 
  GL_EXT_texture_edge_clamp, GL_EXT_texture_env_add, 
  GL_EXT_texture_env_combine, GL_EXT_texture_env_dot3, 
  GL_EXT_texture_filter_anisotropic, GL_EXT_texture_lod, 
  GL_EXT_texture_lod_bias, GL_EXT_texture_object, GL_EXT_vertex_array, 
  GL_HP_occlusion_test, GL_IBM_texture_mirrored_repeat, 
  GL_KTX_buffer_region, GL_NV_blend_square, GL_NV_copy_depth_to_color, 
  GL_NV_depth_clamp, GL_NV_fence, GL_NV_fog_distance, 
  GL_NV_light_max_exponent, GL_NV_multisample_filter_hint, 
  GL_NV_occlusion_query, GL_NV_packed_depth_stencil, GL_NV_pixel_data_range, 
  GL_NV_point_sprite, GL_NV_register_combiners, GL_NV_register_combiners2, 
  GL_NV_texgen_reflection, GL_NV_texture_compression_vtc, 
  GL_NV_texture_env_combine4, GL_NV_texture_rectangle, GL_NV_texture_shader, 
  GL_NV_texture_shader2, GL_NV_texture_shader3, GL_NV_vertex_array_range, 
  GL_NV_vertex_array_range2, GL_NV_vertex_program, GL_NV_vertex_program1_1, 
  GL_NVX_ycrcb, GL_SGIS_generate_mipmap, GL_SGIS_multitexture, 
  GL_SGIS_texture_lod, GL_SGIX_depth_texture, GL_SGIX_shadow

So anubis, you must be mistaken. Unless you were running in software mode.

[anubis]

i swear to god i saw it running on a gf4 smoothly...

[Vifani]

Hi guys,

I have some news for you. I have used Cg for a simple Per Pixel lighting system (specular + diffuse) and it works very well.

[anubis]

i have tried using cg but droped it again...
you should rather rely on fragmen/vertex programs. you could use the cg compiler to generate those and hand optimize them. please don't use the cg runtime. also writing the assembler programs isn't much harder if you are used to it, believe me. i won't touch a hlsl again until glslang is out.

[Noor]

Why? What's wrong with Cg?

[anubis]

- their runtime library sux ( imo ). it's way overcomplicated for no good reason
- it's still buggy
- looking at the glslang spec you will notice that it's design is much clearer
- overall CG is just a big PR campaing to promte nvidias line of gforce cards

[Noor]

But Cg supports both OpenGL and DirectX.
glslang is only for opengl.

ain't I right?

[anubis]

i was being ignorant about DirectX since i don't use it... you are right if you want to write shaders for both you could make use of cg... but still i would use it just as a compiler and run the generated shaders after i went through them by hand

[Vifani]

I think Cg is very easy to use. I have implementated a per pixel lighting (diffuse + specular without bump mapping) in only 3 hours. So I haven't found it overcomplicated.

Where can I find glslang spec ?

[baldurk]

Unless it's changed since I checked, the Cg toolkit for linux is terrible. The documentation also seemed quite poor, although to be fair I didn't really look into that much after the toolkit. Assuming this is still true, this negates the quality of OpenGL I like (second) best - portability. GLSlang will be true OpenGL, and won't require any additional libraries. I never like having too many libraries hanging around.

[CyraX]

baldurk you are right about only a part of the complaint regarding the CG tookit for GNU/LINUX. The documentation is bad wrt getting CG started on GNU/Linux. The rest of it is just a matter of being able to read thru the standard CG Toolkit pdf.

However you should understand one thing - CG is not supported for Fragment shaders (or pixel shaders) by ATI. So that puts you pretty much in a fix.
Cg is elegant yes. It helps in faster coding - not really.
GLSlang - find it in opengl.org its a link on the right.