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OrangyTang
05-26-2009, 06:18 AM
So I had a user report a problem when running on their X3100 chipset, as glActiveTexture doesn't appear to be available. Here's the stats dump from their machine:


Graphics vendor: Intel GMA X3100 OpenGL Engine
Graphics renderer: Intel Inc.
OpenGL version: 1.2 APPLE-1.5.44

OpenGL max texture size (GL_MAX_TEXTURE_SIZE): 2048
OpenGL multitexture units (GL_MAX_TEXTURE_UNITS): 1

OpenGL Extensions:
GL_ARB_transpose_matrix
GL_ARB_vertex_program
GL_ARB_vertex_blend
GL_ARB_window_pos
GL_ARB_shader_objects
GL_ARB_vertex_shader
GL_ARB_shading_language_100
GL_EXT_multi_draw_arrays
GL_EXT_clip_volume_hint
GL_EXT_rescale_normal
GL_EXT_draw_range_elements
GL_EXT_fog_coord
GL_EXT_gpu_program_parameters
GL_EXT_geometry_shader4
GL_EXT_transform_feedback
GL_APPLE_client_storage
GL_APPLE_specular_vector
GL_APPLE_transform_hint
GL_APPLE_packed_pixels
GL_APPLE_fence
GL_APPLE_vertex_array_object
GL_APPLE_vertex_program_evaluators
GL_APPLE_element_array
GL_APPLE_flush_render
GL_APPLE_aux_depth_stencil
GL_NV_texgen_reflection
GL_NV_light_max_exponent
GL_IBM_rasterpos_clip
GL_SGIS_generate_mipmap
GL_ARB_texture_env_crossbar
GL_ARB_texture_border_clamp
GL_ARB_multitexture
GL_ARB_texture_env_add
GL_ARB_texture_cube_map
GL_ARB_texture_env_dot3
GL_ARB_texture_env_combine
GL_ARB_texture_compression
GL_ARB_texture_mirrored_repeat
GL_ARB_shadow
GL_ARB_depth_texture
GL_ARB_fragment_program
GL_ARB_fragment_program_shadow
GL_ARB_fragment_shader
GL_ARB_occlusion_query
GL_ARB_point_sprite
GL_ARB_texture_non_power_of_two
GL_ARB_vertex_buffer_object
GL_ARB_pixel_buffer_object
GL_ARB_draw_buffers
GL_EXT_framebuffer_object
GL_EXT_framebuffer_blit
GL_EXT_texture_rectangle
GL_ARB_texture_rectangle
GL_EXT_texture_env_add
GL_EXT_blend_color
GL_EXT_blend_minmax
GL_EXT_blend_subtract
GL_EXT_texture_lod_bias
GL_EXT_abgr
GL_EXT_bgra
GL_EXT_stencil_wrap
GL_EXT_texture_filter_anisotropic
GL_EXT_separate_specular_color
GL_EXT_secondary_color
GL_EXT_blend_func_separate
GL_EXT_shadow_funcs
GL_EXT_stencil_two_side
GL_EXT_texture_compression_s3tc
GL_EXT_texture_compression_dxt1
GL_EXT_texture_sRGB
GL_EXT_blend_equation_separate
GL_EXT_packed_depth_stencil
GL_APPLE_flush_buffer_range
GL_APPLE_ycbcr_422
GL_APPLE_vertex_array_range
GL_APPLE_texture_range
GL_APPLE_pixel_buffer
GL_APPLE_object_purgeable
GL_NV_blend_square
GL_ATI_texture_env_combine3
GL_SGIS_texture_edge_clamp
GL_SGIS_texture_lod

Now I'd decided that minimum specs for my game would be two-texture multitexturing, on the basis that every desktop/laptop chip has supported that for years, but that doesn't seem to be the case here. The dump says that it supports GLSL shaders, VBOs, FBOs and multitexturing, yet the GL version is way down at 1.2, and the number of multitexturing units is only one (which begs the question, why include the GL_ARB_multitexture extension at all?).

What's going on here? Is this an accurate reflection of the actual hardware capabilities or some crazy intel/apple driver quirk? Hard information on this card seems a little difficult to come by, but it seems recent (released ~2007 from what I can tell) and the driver version seems up to date too.

Any information and hints as to how to deal with this appreciated. Thanks.

Jackis
05-26-2009, 07:20 AM
I think, somebody in their drivers developer group is not very orderly person. They implemented VS+GS+FS, but didn't want to be in a stew with fixed pipeline functionality support, and that's all.
Broadly speaking, that's not a problem at all. You can write shaders. I might say, you have to write shaders. If you look forward in bright future of GL 3.X or DX1X, there you wouldn't have fixed pipeline functionality at all.

Ilian Dinev
05-26-2009, 08:02 AM
Intel's non-linux drivers have always been flashy (lying) in their hw-caps reports.

As glActiveTexture is missing, then you're completely out of luck.

OrangyTang
05-26-2009, 08:13 AM
I think, somebody in their drivers developer group is not very orderly person. They implemented VS+GS+FS, but didn't want to be in a stew with fixed pipeline functionality support, and that's all.
Not very helpful from a backwards compatibility point of view though. And why advertise ARB_Multitexture if it only has one multitexture unit?


Broadly speaking, that's not a problem at all. You can write shaders. I might say, you have to write shaders. If you look forward in bright future of GL 3.X or DX1X, there you wouldn't have fixed pipeline functionality at all.
Ironically I didn't base the rendering around shaders because it's just a 2d game and I wanted to support intel chips without GLSL. Now I'm in the odd position where I've got a fixed function path which works on nVidia, ATi and older intel chips, but not this newer one.

I really don't want to write an entirely new render path because intel's driver team are too damn lazy to maintain backwards compatibility, however it seems rude to users to pop up a message saying "I'm sorry your intel chip is too new to play this game".

overlay
05-26-2009, 08:23 AM
Multitexturing is core feature in OpenGL 1.3. With OpenGL<1.3 you have to deal with extension GL_ARB_multitexture and functions like glActiveTextureARB().


Still, even if you use the ARB extension, this reported line shows you with not be able to do much with it:

OpenGL multitexture units (GL_MAX_TEXTURE_UNITS): 1

... and this is not conform to the spec. Spec 1.3 states that the minimum value for GL_MAX_TEXTURE_UNITS should be 2 (Table 6.29, Implementation Dependent Values).

arekkusu
05-26-2009, 09:25 AM
Something is wrong with your query. See MAX_TEXTURE_UNITS in the GLinfo table (http://homepage.mac.com/arekkusu/bugs/GLInfo.html).

It really supports 16 samplers, as indicated by MAX_TEXTURE_IMAGE_UNITS_ARB. Only 8 are exposed for fixed function.

OrangyTang
05-26-2009, 09:45 AM
Something is wrong with your query. See MAX_TEXTURE_UNITS in the GLinfo table (http://homepage.mac.com/arekkusu/bugs/GLInfo.html).

It really supports 16 samplers, as indicated by MAX_TEXTURE_IMAGE_UNITS_ARB. Only 8 are exposed for fixed function.


Now that's a useful table, thanks. So the 1.2 gl version is expected, I'll see if I can find anything suspicious going on in my texture units query.