WebGL attribute is always null - webgl

Question

I'm trying to make a graphic engine in WebGL, but I'm having lots of trouble.
One of this problems is about attributes being null or -1 when I call them with "gl.getUniformLocation".
My main problem with this right now is "aVertexTextureCoords", which is always -1.
I leave here my shaders, just in case they're the problem.
<script id="shader-vs" type="x-shader/x-vertex">
attribute vec3 aVertexPosition;
attribute vec3 aVertexNormal;
attribute vec4 aVertexColor;
attribute vec2 aVertexTextureCoords;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
uniform mat4 uNMatrix;
uniform float uAlpha;
const int NUM_LIGHTS = 4;
uniform vec4 uMaterialDiffuse;
uniform vec3 uLightPosition[NUM_LIGHTS];
//varyings
varying vec4 vColor;
varying vec2 vTextureCoord;
varying vec3 vNormal;
varying vec3 vLightRay[NUM_LIGHTS];
void main(void) {
//Transformed vertex position
vec4 vertex = uMVMatrix * vec4(aVertexPosition, 1.0);
//Transformed normal position
vNormal = vec3(uNMatrix * vec4(aVertexNormal, 1.0));
//Calculate light ray per each light
for(int i=0; i < NUM_LIGHTS; i++){
vec4 lightPosition = uMVMatrix * vec4(uLightPosition[i], 1.0);
vLightRay[i] = vertex.xyz - lightPosition.xyz;
}
//Final vertex position
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vTextureCoord = aVertexTextureCoords;
}
</script>
<script id="shader-fs" type="x-shader/x-fragment">
#ifdef GL_ES
precision highp float;
#endif
//object uniforms
uniform bool uWireframe;
uniform vec4 uMaterialAmbient;
uniform vec4 uMaterialDiffuse;
//Incluimos un uniform que asociara la textura a un uniform
uniform sampler2D uSampler;
//light uniforms
const int NUM_LIGHTS = 4;
uniform bool uLightSource;
uniform vec4 uLightAmbient;
uniform vec4 uLightDiffuse[NUM_LIGHTS];
uniform float uCutOff;
//varyings
varying vec2 vTextureCoord;
varying vec3 vNormal;
varying vec3 vLightRay[NUM_LIGHTS];
void main(void)
{
if(uWireframe || uLightSource){
gl_FragColor = uMaterialDiffuse;
}
else{
vec4 Ia = uLightAmbient * uMaterialAmbient; //Ambient component: one for all
vec4 finalColor = vec4(0.0,0.0,0.0,1.0); //Color that will be assigned to gl_FragColor
vec3 N = normalize(vNormal);
vec3 L = vec3(0.0);
float lambertTerm = 0.0;
for(int i = 0; i < NUM_LIGHTS; i++){ //For each light
L = normalize(vLightRay[i]); //Calculate reflexion
lambertTerm = dot(N, -L);
if (lambertTerm > uCutOff){
finalColor += uLightDiffuse[i] * uMaterialDiffuse *lambertTerm; //Add diffuse component, one per light
}
}
//Final color
finalColor += Ia;
finalColor.a = 1.0; //Add ambient component: one for all
gl_FragColor = finalColor * texture2D(uSampler, vTextureCoord); //The alpha value in this example will be 1.0
}
}
</script>
Can somebody tell me what I'm doing wrong?

Answer 1

Calling gl.getUniformLocation for a vertex attribute is wrong because it's an attribute, not a uniform. Replace the call with gl.getAttribLocation.