diff options
| -rw-r--r-- | src/mesa/main/get.c | 4 | ||||
| -rw-r--r-- | src/mesa/main/texcompress.c | 117 | ||||
| -rw-r--r-- | src/mesa/main/texcompress.h | 2 |
3 files changed, 93 insertions, 30 deletions
diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c index 0492e1585c3..d32c68a53a4 100644 --- a/src/mesa/main/get.c +++ b/src/mesa/main/get.c @@ -1569,11 +1569,11 @@ find_custom_value(struct gl_context *ctx, const struct value_desc *d, union valu break; case GL_NUM_COMPRESSED_TEXTURE_FORMATS_ARB: - v->value_int = _mesa_get_compressed_formats(ctx, NULL, GL_FALSE); + v->value_int = _mesa_get_compressed_formats(ctx, NULL); break; case GL_COMPRESSED_TEXTURE_FORMATS_ARB: v->value_int_n.n = - _mesa_get_compressed_formats(ctx, v->value_int_n.ints, GL_FALSE); + _mesa_get_compressed_formats(ctx, v->value_int_n.ints); ASSERT(v->value_int_n.n <= 100); break; diff --git a/src/mesa/main/texcompress.c b/src/mesa/main/texcompress.c index 040be943e82..42bd1eee5ca 100644 --- a/src/mesa/main/texcompress.c +++ b/src/mesa/main/texcompress.c @@ -131,16 +131,101 @@ _mesa_gl_compressed_format_base_format(GLenum format) * Return list of (and count of) all specific texture compression * formats that are supported. * + * Some formats are \b not returned by this function. The + * \c GL_COMPRESSED_TEXTURE_FORMATS query only returns formats that are + * "suitable for general-purpose usage." All texture compression extensions + * have taken this to mean either linear RGB or linear RGBA. + * + * The GL_ARB_texture_compress_rgtc spec says: + * + * "19) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and + * GL_COMPRESSED_TEXTURE_FORMATS queries return the RGTC formats? + * + * RESOLVED: No. + * + * The OpenGL 2.1 specification says "The only values returned + * by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those + * corresponding to formats suitable for general-purpose usage. + * The renderer will not enumerate formats with restrictions that + * need to be specifically understood prior to use." + * + * Compressed textures with just red or red-green components are + * not general-purpose so should not be returned by these queries + * because they have restrictions. + * + * Applications that seek to use the RGTC formats should do so + * by looking for this extension's name in the string returned by + * glGetString(GL_EXTENSIONS) rather than + * what GL_NUM_COMPRESSED_TEXTURE_FORMATS and + * GL_COMPRESSED_TEXTURE_FORMATS return." + * + * There is nearly identical wording in the GL_EXT_texture_compression_rgtc + * spec. + * + * The GL_EXT_texture_rRGB spec says: + * + * "22) Should the new COMPRESSED_SRGB_* formats be listed in an + * implementation's GL_COMPRESSED_TEXTURE_FORMATS list? + * + * RESOLVED: No. Section 3.8.1 says formats listed by + * GL_COMPRESSED_TEXTURE_FORMATS are "suitable for general-purpose + * usage." The non-linear distribution of red, green, and + * blue for these sRGB compressed formats makes them not really + * general-purpose." + * + * The GL_EXT_texture_compression_latc spec says: + * + * "16) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and + * GL_COMPRESSED_TEXTURE_FORMATS queries return the LATC formats? + * + * RESOLVED: No. + * + * The OpenGL 2.1 specification says "The only values returned + * by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those + * corresponding to formats suitable for general-purpose usage. + * The renderer will not enumerate formats with restrictions that + * need to be specifically understood prior to use." + * + * Historically, OpenGL implementation have advertised the RGB and + * RGBA versions of the S3TC extensions compressed format tokens + * through this mechanism. + * + * The specification is not sufficiently clear about what "suitable + * for general-purpose usage" means. Historically that seems to mean + * unsigned RGB or unsigned RGBA. The DXT1 format supporting alpha + * (GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) is not exposed in the list (at + * least for NVIDIA drivers) because the alpha is always 1.0 expect + * when it is 0.0 when RGB is required to be black. NVIDIA's even + * limits itself to true linear RGB or RGBA formats, specifically + * not including EXT_texture_sRGB's sRGB S3TC compressed formats. + * + * Adding luminance and luminance-alpha texture formats (and + * certainly signed versions of luminance and luminance-alpha + * formats!) invites potential comptaibility problems with old + * applications using this mechanism since old applications are + * unlikely to expect non-RGB or non-RGBA formats to be advertised + * through this mechanism. However no specific misinteractions + * with old applications is known. + * + * Applications that seek to use the LATC formats should do so + * by looking for this extension's name in the string returned by + * glGetString(GL_EXTENSIONS) rather than + * what GL_NUM_COMPRESSED_TEXTURE_FORMATS and + * GL_COMPRESSED_TEXTURE_FORMATS return." + * + * There is no formal spec for GL_ATI_texture_compression_3dc. Since the + * formats added by this extension are luminance-alpha formats, it is + * reasonable to expect them to follow the same rules as + * GL_EXT_texture_compression_latc. At the very least, Catalyst 11.6 does not + * expose the 3dc formats through this mechanism. + * * \param ctx the GL context * \param formats the resulting format list (may be NULL). - * \param all if true return all formats, even those with some kind - * of restrictions/limitations (See GL_ARB_texture_compression - * spec for more info). * * \return number of formats. */ GLuint -_mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats, GLboolean all) +_mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats) { GLuint n = 0; if (ctx->Extensions.TDFX_texture_compression_FXT1) { @@ -152,24 +237,15 @@ _mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats, GLboolean a n += 2; } } - /* don't return RGTC - ARB_texture_compression_rgtc query 19 */ + if (ctx->Extensions.EXT_texture_compression_s3tc) { if (formats) { formats[n++] = GL_COMPRESSED_RGB_S3TC_DXT1_EXT; - /* This format has some restrictions/limitations and so should - * not be returned via the GL_COMPRESSED_TEXTURE_FORMATS query. - * Specifically, all transparent pixels become black. NVIDIA - * omits this format too. - */ - if (all) - formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT; formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT; formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT; } else { n += 3; - if (all) - n += 1; } } if (ctx->Extensions.S3_s3tc) { @@ -183,19 +259,6 @@ _mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats, GLboolean a n += 4; } } -#if FEATURE_EXT_texture_sRGB - if (ctx->Extensions.EXT_texture_sRGB) { - if (formats) { - formats[n++] = GL_COMPRESSED_SRGB_S3TC_DXT1_EXT; - formats[n++] = GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT; - formats[n++] = GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT; - formats[n++] = GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT; - } - else { - n += 4; - } - } -#endif /* FEATURE_EXT_texture_sRGB */ return n; #if FEATURE_ES1 || FEATURE_ES2 diff --git a/src/mesa/main/texcompress.h b/src/mesa/main/texcompress.h index 922da00912d..375cf90c8a2 100644 --- a/src/mesa/main/texcompress.h +++ b/src/mesa/main/texcompress.h @@ -37,7 +37,7 @@ extern GLenum _mesa_gl_compressed_format_base_format(GLenum format); extern GLuint -_mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats, GLboolean all); +_mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats); extern gl_format _mesa_glenum_to_compressed_format(GLenum format); |