Shader crashing

Newbie & Debugging Questions
#1

Hi,

I have a default vertex shader where I’m trying to pass in an attribute of type float: (nightCol)


attribute float nightCol;
attribute vec4 a_position;
attribute vec4 a_color;
attribute vec2 a_texCoord0;
uniform mat4 u_projTrans;
varying float vNightCol;
varying vec4 vColor;
varying vec2 vTexCoord;

void main() {
    vNightCol = nightCol;
	vColor = a_color;
	vTexCoord = a_texCoord0;
	gl_Position = u_projTrans * a_position;		
}

And a fragment shader:


#ifdef GL_ES
#define LOWP lowp
precision mediump float;
#else
#define LOWP
#endif

uniform sampler2D u_texture;

varying vec4 vColor;
varying vec2 vTexCoord;
varying float vNightCol;

const vec3 grayScaleMultiplier = vec3(0.299, 0.587, 0.114);

void main() {
  vec4 texColor = texture2D(u_texture, vTexCoord);
  vec3 gray = vec3(dot(texColor.rgb, grayScaleMultiplier));
  gl_FragColor = vec4(gray.r, gray.g, gray.b, texColor.a * vNightCol);
}

I set the attribute up as follows:


		nightShader.begin();
		nightShader.setAttributef("nightCol", nightCol,0,0,0);
		nightShader.end();

Exception I get: java.lang.IllegalArgumentException: no uniform with name ‘u_projTrans’ in shader

It is as though it isn’t finding nightCol which I thought would be passed through from the vertex shader to the pixel shader?

Logging the error after checking compilation fails on the shader I get:

Shader: The fragment shader uses varying vNightCol, but previous shader does not write to it.

Any help is appreciated.

Thanks