WebGL: passing uniform arrays to shader

Question

Tried to do just like here: Pass array to shader And like here: Passing an array of vectors to a uniform

But still no luck. I think I do just like there but it doesn't work:

Here's my JavaScript code:

shaderProgram.lightsUniform = gl.getUniformLocation(shaderProgram, "lights"); // Getting location
gl.uniform1f(shaderProgram.lightsUniform, new Float32Array([3,1,2,3,4,5])); // Let's try to send some light (currently each light is one float) as array.

Vertex Shader Code:

uniform float lights[6]; // Declaration

...

vLight *= lights[0]; // Let's try to mutliply our light by the first array item. There should be 3.0.

Summary: I send an array to shader with non-zero-floats.

Result: totally black! I.e. lights[0] contains 0.0 but expected 3.0. If I try lights[1], lights[2] etc. they all give the same result!

Let's now try to pass just one float. I change

gl.uniform1f(shaderProgram.lightsUniform, new Float32Array([3,1,2,3,4,5]));

to

gl.uniform1f(shaderProgram.lightsUniform, 3); // I want to send just float 3.0

Summary: instead of sending array I send just float 3.0.

Result: works! lights[0] contains 3.0 (but I sent just float, not an array).

What do I do wrong? How do I pass to shader array of uniforms?

score 10 · Accepted Answer · edited Apr 30 '22 at 14:17

10

Those answers all use the function uniform3fv. v as in vector.

So you should be using uniform1fv, not uniform1f for arrays of uniforms.

edited Apr 30 '22 at 14:17

George Savva

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answered Jul 26 '13 at 00:27

Nicol Bolas

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I experienced a similar issue. But when I changed to uniform1fv, I got the following console error: Failed to execute 'uniform1fv' on 'WebGLRenderingContext': No function was found that matched the signature provided. – InfiniteStack May 24 '17 at 21:21
27

"check your OpenGL errors before asking questions" This is an inherently challenging space and can be incredibly overwhelming. This is well formed question, with a helpful and direct answer, which is the point of StackOverflow. There's no reason to tell someone they shouldn't ask a question. – Matthew May 21 '20 at 11:24

score -3 · Answer 2 · answered Nov 30 '17 at 01:29

1: Make sure your if statement is within a function.

2: Make sure precision is set before declaring uniforms.

      #ifdef GL_FRAGMENT_PRECISION_HIGH
        precision highp float;
      #else
        precision mediump float;
      #endif
      precision mediump int;

3: Make sure comparison is of correct type:

This will FAIL:

uniform vec3 neon_whatever;
if(neon_whatever.x == 0){

};

This will FAIL:

uniform vec3 neon_whatever;
if(neon_whatever == 0.0){

};

This will WORK:

uniform vec3 neon_whatever;
if(neon_whatever.x == 0.0){

};

WebGL: passing uniform arrays to shader

2 Answers2