CODEWITHSUNDEEP
javascriptglslwebgl
kishoredbn
kishoredbn

Reputation: 2087

Error in GLSL program - WebGL

I was trying to pass an uniform variable from my JavaScript code to GSLS program. But I am getting this warning, for which my expected output is not coming: 

WebGL: INVALID_OPERATION: uniform3fv: location is not from current program

There is how I have initialised the uniform value from my JavaScript code:

var lights = {
    direction: [1.0, 1.0, 1.0],
    color: [0.0, 1.0, 1.0]
};

var u_LightColor = gl.getUniformLocation(program, 'u_LightColor');
var u_LightDirection = gl.getUniformLocation(program, 'u_LightDirection');

if (u_LightColor < 0) {
    console.error("failed to get the storage location u_LightColor");
}

if (u_LightDirection < 0) {
    console.error("failed to get the storage location u_LightDirection");
}

gl.uniform3fv(u_LightColor, lights.color);
gl.uniform3fv(u_LightDirection, lights.direction);

My fragment-shader code is like this:

precision mediump float;
    uniform vec3 u_LightColor;
    uniform vec3 u_LightDirection;
    uniform sampler2D diffuseMap;
    varying mediump vec3 color;
    varying vec2 tCoord;
    varying vec3 n;
    void main(void) {

        vec3 normal = normalize(n);
        float nDotL = max(dot(normalize(vec3(-5.0, -0.0, -5.0)), normal), 0.0);
        diffuseVal = (u_LightColor) * diffuseVal * nDotL;
        gl_FragColor = vec4(diffuseVal, 1.0);
    }

I don't know why I am getting this warning. Although the program is running but the values of u_LightColor or u_LightDirection is not passing into fragment-shader; as a result output is all dark.

Also to point out, I have other uniform variable in the GLSL program in which data is passed using uniformSetter function; and those are working fine.

Can someone help me know, why data is not coming in u_LightColor or u_LightDirection?

Upvotes: 0

Views: 1472

Answers (1)

user128511
user128511

Reputation:

Did you call gl.useProgram(program) before calling gl.uniform3fv?

Uniforms are program specific. In other words if I make 2 shader programs, even if they use exactly the same source, the locations that are looked up for them are not sharable.

Example: given these functions which always use the same source.

 function makeShader(type, source) {
    var s = gl.createShader(type);
    gl.shaderSource(s, source);
    gl.compileShader(s);
    return s;
 }

 function makeProgram() {
    var vs = makeShader(gl.VERTEX_SHADER, vertexShaderSource);
    var fs = makeShader(gl.FRAGMENT_SHADER, fragmentShaderSource);
    var prg = gl.createProgram();
    gl.attachShader(vs);
    gl.attachShader(fs);
    gl.linkShader(prg);
    return prg;
 }

This code will generate an error

 var prg1 = makeProgram();
 var prg2 = makeProgram();
 var u_someUniformLocation = gl.getUniformLocation(prg1, "u_someUniform");

 gl.useProgram(prg2);
 gl.uniform3fv(u_someUniformLocation, [1,2,3]);  // ERROR!

u_someUniformLocation is for prg1 not prg2 even though the shader programs are the same they are separate programs and have require separate WebGLUniformLocation objects.

Upvotes: 4

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