Hello

I want to flip the normals in a custom shader but I’ve some trooble making it work. I’ve try some tutorials but from my understanding each engine handle glsl differently. So here is the code.

**The fragment shader**

```
varying vec2 vUv0;
uniform sampler2D uDiffuseMap;
varying mat4 matrix_model;
varying vec4 verpos;
varying float effect;
void main(void)
{
gl_FragColor = vec4(0.0);
vec4 color = texture2D(uDiffuseMap, vUv0);
color = vec4(color.x+ ((verpos.y*0.0009) * (effect - 0.9) * 2.0), color.y+ ((verpos.y*0.0009) * (effect - 0.9) * 2.0),color.z+((verpos.y*0.0009) * (effect - 0.90) * 2.0),1);
gl_FrontFacing = false;
gl_FragColor = color;
}
```

**The Vertex shader**

```
attribute vec3 aPosition;
attribute vec2 aUv0;
varying vec2 texCoord;
uniform mat4 matrix_model;
uniform mat4 matrix_viewProjection;
uniform float scale;
varying float effect;
varying vec2 vUv0;
varying vec4 verpos;
void main(void)
{
effect = scale;
vUv0 = aUv0;
verpos = vec4(aPosition ,scale);
gl_Position = matrix_viewProjection * matrix_model * vec4(aPosition ,scale);
}
```

[the link I followed] (http://stackoverflow.com/questions/28160756/normals-are-inverted)

I’ve a compilation error on the **gl_FontFacing = false;**. Is there any other way I can access this function.

I tried to find some documentation about it but couldn’t find one wich actually work on playcanvas. Is it beceause it is on web gl?

that’s a lot of questions and i’m a bit noob in shader programming. If anyone can link me to a documentation that would be great

thanks!