NAME

shader_ugroup - Allocate a uniform group inside a shader

SYNOPSIS

out_shid or nil
shader_ugroup( shid )

DESCRIPTION

All shaders have a default group of shaders that the shader_uniform function applies to. In many cases, however, one might want to have multiple objects that uses the same shader but with a slightly different set of uniforms. shader_ugroup can be used to create a derivative shader that uses most of the same underlying resources but switches to a different set of uniforms when activated. The returned shader is valid for all shader related calls but has its lifecycle to the shader it was derived from. Any forced uniform at the time of group creation will be copied from the group associated with the specified shid. There's a finite amount of uniform group slots available to each shader, and if the provided shid is invalid or there are not enough free group slots left in the shader, the out_shid will be nil.

NOTES

1

Though it is bad form to ever rely in the specific value of a shid, shaders that are derived typically have a value > 65535.

EXAMPLE

function shader_ugroup0()


      local frag = [[


            uniform float r;


            uniform float g;


            uniform float b;


            void shader_ugroup0(){


                  gl_FragColor = vec4(r, g, b, 1.0);


            }
]];


      local shid = build_shader(nil, frag, "csh");


      a = fill_surface(64, 64, 0, 0, 0);


      b = fill_surface(64, 64, 0, 0, 0);


      show_image({a, b});


      move_image(b, 64, 0);


      image_shader(a, shid);


      shader_uniform(shid, "r", "f", 1.0);


      shader_uniform(shid, "b", "f", 0.0);
-- r and b values will be inherited, g is undefined


      local shid2 = shader_ugroup(shid);


      image_shader(b, shid2);
-- g is now defined in shid1, undefined in shid2


      shader_uniform(shid, "g", "f", 1.0);


      shader_uniform(shid2, "g", "f", 0.0);
end

SEE ALSO:

build_shader(3) delete_shader(3)