This is a shader I use to add extra detail to a low resolution texture. You can think of it as colour keying. Running this shader is costing me about 6fps and I think it’s because of the way I use the dynamic branching. Any idea’s on speeding it up?
I did a test were the if’s were always true and it ran quicker so it’s not the extra texture sampling, I think…
My best bet is to use lessThan function cast the result to a vec4 and do a mix.
For example
vec3 diff = texel.xyz - detail_mapping[0].xyz;
vec3 replace = lessThan(dot(diff,diff),detail_mapping[0].www);
texel.xyz = mix(texel.xyz, texture2D(tex_sampler1,v_texcoord_detail),replace);
But for just doing a simple “replace colour with another colour if colour == A_value” seems a lot of work.
precision lowp float;
uniform bvec4 flags;
uniform sampler2D tex_sampler0;
uniform vec4 fog_colour;
uniform vec4 detail_mapping[2];
uniform sampler2D tex_sampler1;
uniform sampler2D tex_sampler2;
varying mediump vec2 v_texcoord;
varying mediump vec2 v_texcoord_detail;
varying vec4 v_colour;
varying float v_fog_factor;
void main()
{
vec4 texel = texture2D(tex_sampler0,v_texcoord);
vec3 diff = texel.xyz - detail_mapping[0].xyz;
if( dot(diff,diff) < detail_mapping[0].w )
{
texel = texture2D(tex_sampler1,v_texcoord_detail);
}
diff = texel.xyz - detail_mapping[1].xyz;
if( dot(diff,diff) < detail_mapping[1].w )
{
texel = texture2D(tex_sampler2,v_texcoord_detail);
}
gl_FragColor = texel * v_colour;
if( flags[2] )
{
gl_FragColor = mix(fog_colour,gl_FragColor,v_fog_factor);
}
}
I’ve gained an extra 4 to 5 fps using step to do the test and mix to do the replacement.
vec3 diff = texel.xyz - detail_mapping[0].xyz;
float replace = step(dot(diff,diff),detail_mapping[0].w);
texel = mix(texel,texture2D(tex_sampler1,v_texcoord_detail),replace);
I would have thought the compiler would have done the same???
