Uniform locations return -1

Newbie & Debugging Questions
#1

Sorry for all the GLSL topics, I’m having bug after bug…

My fragment shader has two uniform samplers:


...
uniform sampler2D t_diffuse;
uniform sampler2D t_specular;
...
 
void main() {
	vec4 diffuse = texture2D(t_diffuse, gl_TexCoord[0].st).rgba;
	vec4 specular = texture2D(t_specular, gl_TexCoord[0].st).rgba;
	...	
   gl_FragColor = specular;
}

I access them with: (Per frame)


   glActiveTexture(GL_TEXTURE0);
	testTexture.bind();
	texLoc = glGetUniformLocation(world.getLightingProgram().programID, "t_diffuse");
	glUniform1f(texLoc,  testTexture.id);
	if(texLoc < 0) System.out.println("Error accessing diffuse: " + texLoc);
			
	glActiveTexture(GL_TEXTURE1);
	testSpecular.bind(); //glBindTexture(GL_TEXTURE_2D, id); - Works...
	texLoc = glGetUniformLocation(world.getLightingProgram().programID, "t_specular");
	glUniform1f(texLoc, testSpecular.id);
   if(texLoc < 0) System.out.println("Error accessing specular: " + texLoc);

And here’s the output:

 Error accessing diffuse: -1

The light shader program ID returns 1. So that works.
The diffuse texture returns 1. (testTexture.id;)
The specular texture return 2. (testSpecular.id;)
But the specular IS working…

#2

As you’ve just ignored the diffuse value… the GLSL compiler has helpfully optimised the whole thing away. Slightly annoying when you’re debugging shaders but that’s what it does.

Cas :slight_smile:

#3

Shouldn’t you use t_diffuse as that is the variable name in the shader, when you access it? I’ve only a few hours experience with GLSL, so correct me if I’m wrong.

#4

Yeah, I just renamed all of them for the sake of the thread, same error.

#5

Also, it seems to be binding the testTexture to the specular sampler.

#6

Okay, I see what you mean, I’m using the specular map but the diffuse map isn’t being used. Thanks for the info!

#7

also, you have to bind the texture unit not the texture id.
GL_Texture0 == 0
GL_Texture1 == 1
…

#8

Thanks, its all working now! Except for the specular mapping. Can anyone please help me out with that?

Heres my shader:

#version 120
varying vec3 normal; 
varying vec3 position;

uniform vec2 lightLocation;
uniform vec3 lightColor;
uniform vec3 ambientLight;

uniform sampler2D t_diffuse;
uniform sampler2D t_specular;

uniform bool material;
 
void main() {
		vec4 diffuse = texture2D(t_diffuse, gl_TexCoord[0].st);
		vec4 specular = texture2D(t_specular, gl_TexCoord[0].st);
		
        float distance = length(lightLocation - gl_FragCoord.xy);
        float attenuation = 1.0 / distance;
        vec4 light = vec4(attenuation, attenuation, attenuation, pow(attenuation, 3)) * vec4(lightColor, 1);
        
        vec4 color;
        
        if(material)
        light += specular;
 		color = light * diffuse;
 		if(!material)
 		color = light;
 		
        gl_FragColor = color;
}
#9

You are using a strange combination of the modern and deprecated pipelines.