How to use glUniform1f in this example?

Question

I've searched for, read and tried many different examples on how to pass a value into a GLSL program. But sadly every try was a fail :( What I plan to do is very simple: Just a little open gl 3d animation inside my Android App. Resulting from my GUI design I prefer to use a TextureView as OpenGl Surface. I found some code that fits perfect to my project. But my problem seems to be completely inside this example. When I compile and run it, it does exactly what it is supposed to do. Draw one single triangle on screen. Then I modified the Vertex Shader like this: ``` final String vertexShaderSource = "attribute vec4 position;
" + "attribute float myValue;
" + "void main () {
" + "vec4 oo;
"+ "oo[0] = position[0];
"+ "oo[1] = position[1] * myValue;
"+ "oo[2] = position[2];
"+ "oo[3] = position[3];
"+ "gl_Position = oo;
" + "}"; ``` And now, I want to pass a value to the attribute `myValue`. So here are my modifications to the run method. ``` public void run() { initGL(); int attr…

Accepted Answer

You're mixing the concepts of `attribute` and `uniform` variables.

Since you declared your `myValue` variable as an `attribute` in the shader, you need to set the value with `glVertexAttrib()`:

```
glVertexAttrib1f(valuePosition, 1.5f);
```

If you want it to be a `uniform`, change the declaration in the vertex shader to:

```
uniform float myValue;
```

and the call to get the location to:

```
int valuePosition = GLES20.glGetUniformLocation(mProgram, "myValue");
```

Both solutions are valid. As the name suggests, `uniform` variables are ideal for values that do not change much, i.e. they ideally stay the same for the whole frame. `attribute` variables are more efficient for values that change frequently while rendering a frame.

How to use glUniform1f in this example?

Solution

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