bump mapping with 2 normal maps

Question

I was wondering if its actually possible to do bump mapping with 2 normal maps... I have tried doing it this way however I get a function overload on max and dot.

uniform sampler2D  n_mapTex;
uniform sampler2D  n_mapTex2;
uniform sampler2D  refTex;

varying mediump vec2  TexCoord;
varying mediump float vTime;

void main()
{   
    mediump vec4 wave = texture2D(n_mapTex, TexCoord - vTime);
    mediump vec4 wave2 = texture2D(n_mapTex2, TexCoord + vTime);
    mediump vec4 bump = mix(wave2, wave, 0.5);
    //this extracts the normals from the combined normal maps
    mediump vec4 normal = normalize(bump.xyzw * 2.0 - 1.0);
    //determines light position
    mediump vec3 lightPos = normalize(vec3(0.0, 1.0, 3.0));

    mediump float diffuse = max(dot(normal, lightPos),0.0);
    gl_FragColor = mix(texture2D(refTex, TexCoord), bump, 0.5);
}

Answer 1

I'm not really sure what exactly you hope to achieve, the proposition sounds sketchy.

In any case, I'm pretty sure you get your error for trying to calculate the dot product between a vec4 and a vec3. The mathematical dot product is only defined for vectors with the same number of dimensions, most programming languages mirror this.