From my understanding of the code, `mixmap.g`

is the blend factor between texture1/texture2, `mixmap.b`

the blend factor between texture2/texture3 and `1-mixmap.a`

the blend factor between texture3/texture4. `mixmap.r`

is a static multiplication factor for texture1:

```
vec4 mixColor = texture2D(mixMap1Sampler, vTextureUV);
mixColor.rgb *= vTextureInfos.y;
vec4 diffuse1Color = texture2D(diffuse1Sampler, vTextureUV * diffuse1Infos);
vec4 diffuse2Color = texture2D(diffuse2Sampler, vTextureUV * diffuse2Infos);
vec4 diffuse3Color = texture2D(diffuse3Sampler, vTextureUV * diffuse3Infos);
vec4 diffuse4Color = texture2D(diffuse4Sampler, vTextureUV * diffuse4Infos);
diffuse1Color.rgb *= mixColor.r;
diffuse2Color.rgb = mix(diffuse1Color.rgb, diffuse2Color.rgb, mixColor.g);
diffuse3Color.rgb = mix(diffuse2Color.rgb, diffuse3Color.rgb, mixColor.b);
finalMixColor.rgb = mix(diffuse3Color.rgb, diffuse4Color.rgb, 1.0 - mixColor.a);
```