2016-03-31 22:58 GMT+02:00 Henri Verbeet hverbeet@gmail.com:
On 31 March 2016 at 19:51, Matteo Bruni mbruni@codeweavers.com wrote:
- shader_addline(buffer, "if (alpha_test)\n");
- if (alpha_func != WINED3D_CMP_NEVER)
shader_addline(buffer, " if (!(%s[0].a %s alpha_ref))\n",get_fragment_output(gl_info), comparison_operator[alpha_func - WINED3D_CMP_NEVER]);- shader_addline(buffer, " discard;\n");
Is there really an advantage to having the "alpha_test" uniform instead of just mapping disabled alpha test to WINED3D_CMP_ALWAYS?
The advantage is to avoid creating two shader variants for alpha test enabled vs disabled and flipping between the two when the WINED3D_RS_ALPHATESTENABLE state is toggled. I only have some limited empiric evidence but it seems like changing the alpha test function is very rare in practice while toggling the alpha test enabled / disabled is relatively common.
@@ -973,6 +981,7 @@ struct ps_compile_args { WORD texcoords_initialized; /* MAX_TEXTURES, 8 */ BOOL pointsprite; BOOL flatshading;
- enum wined3d_cmp_func alpha_func;
};
enum fog_src_type { @@ -2022,6 +2031,7 @@ struct ffp_frag_settings unsigned char pointsprite : 1; unsigned char flatshading : 1; unsigned char padding : 5;
- enum wined3d_cmp_func alpha_func;
"alpha_func" only needs 4 bits (3 if you just mask the 4th bit), so would still fit in the padding. That applies somewhat to struct ps_compile_args as well, although we may care less there.
Yes, it can be compressed. I'll have a look.