Uniform Variables Display a black screen using jogl

Question

I've been piecing together a basic game engine using jogl and have hit a pretty big road bump when it comes to accessing and/or updating uniform variables in my shader code.

Here is how I am allocating the Matrix and associated Buffer:

protected float[] test_matrix = {
    1.0f, 0.0f, 0.0f, 1.0f,
    0.0f, 1.0f, 0.0f, 1.0f,
    0.0f, 0.0f, 1.0f, 1.0f,
    0.0f, 0.0f, 0.0f, 1.0f
};
protected int matrix_size = test_matrix.length;

FloatBuffer matrix_buffer = Buffers.newDirectFloatBuffer(test_matrix, 0, matrix_size);

Here is the code in question:

shaderProgram = gl.glCreateProgram();
gl.glAttachShader(shaderProgram, vertShader);
gl.glAttachShader(shaderProgram, fragShader);

pmvmatrix = new PMVMatrix();
transmatrix_location = gl.glGetUniformLocation(shaderProgram, "transformationMatrix");
gl.glUniformMatrix4fv(transmatrix_location, 400, false, matrix_buffer);

pmvmatrix.glMatrixMode(GLMatrixFunc.GL_MODELVIEW);
pmvmatrix.glLoadIdentity();

gl.glBindAttribLocation(shaderProgram, 0, "position");
gl.glBindAttribLocation(shaderProgram, 1, "color");

gl.glLinkProgram(shaderProgram);

And here is my vertex shader:

#version 400 core

in vec3 position;

out vec3 color;

uniform mat4 transformationMatrix;

void main(void){
    gl_Position = transformationMatrix * vec4(position,1.0);
    color = vec3(position.x+0.5,1.0,position.y+0.5);
}

The shaders are compiling successfully and if I remove the "transformationMatrix *" in my vertex shader, the object renders properly.

Is my matrix just being passed as a 1X16 matrix rather than a 4X4? Am I using the glUniformMatrix4fv function properly?

genpfault genpfault · Accepted Answer · 2016-12-07T05:55:07

transmatrix_location = gl.glGetUniformLocation(shaderProgram, "transformationMatrix");
...
gl.glLinkProgram(shaderProgram);

Wrong way around. Link, then Get:

... The actual locations assigned to uniform variables are not known until the program object is linked successfully. After linking has occurred, the command glGetUniformLocation can be used to obtain the location of a uniform variable. ...

Uniform Variables Display a black screen using jogl

1 Answers