glsl light doesn't seem to be working - c++

Question

I'm working on some basic lighting in my application, and am unable to get a simple light to work (so far..).
Here's the vertex shader:
#version 150 core
uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
uniform mat4 pvmMatrix;
uniform mat3 normalMatrix;
in vec3 in_Position;
in vec2 in_Texture;
in vec3 in_Normal;
out vec2 textureCoord;
out vec4 pass_Color;
uniform LightSources {
vec4 ambient = vec4(0.5, 0.5, 0.5, 1.0);
vec4 diffuse = vec4(0.5, 0.5, 0.5, 1.0);
vec4 specular = vec4(0.5, 0.5, 0.5, 1.0);
vec4 position = vec4(1.5, 7, 0.5, 1.0);
vec4 direction = vec4(0.0, -1.0, 0.0, 1.0);
} lightSources;
struct Material {
vec4 ambient;
vec4 diffuse;
vec4 specular;
float shininess;
};
Material mymaterial = Material(
vec4(1.0, 0.8, 0.8, 1.0),
vec4(1.0, 0.8, 0.8, 1.0),
vec4(1.0, 0.8, 0.8, 1.0),
0.995
);
void main() {
gl_Position = pvmMatrix * vec4(in_Position, 1.0);
textureCoord = in_Texture;
vec3 normalDirection = normalize(normalMatrix * in_Normal);
vec3 lightDirection = normalize(vec3(lightSources.direction));
vec3 diffuseReflection = vec3(lightSources.diffuse) * vec3(mymaterial.diffuse) * max(0.0, dot(normalDirection, lightDirection));
/*
float bug = 0.0;
bvec3 result = equal( diffuseReflection, vec3(0.0, 0.0, 0.0) );
if(result[0] && result[1] && result[2]) bug = 1.0;
diffuseReflection.x += bug;
*/
pass_Color = vec4(diffuseReflection, 1.0);
}
And here's the fragment shader:
#version 150 core
uniform sampler2D texture;
in vec4 pass_Color;
in vec2 textureCoord;
void main() {
vec4 out_Color = texture2D(texture, textureCoord);
gl_FragColor = pass_Color;
//gl_FragColor = out_Color;
}
I'm rendering a textured wolf to the screen as a test. If I change the fragment shader to use out_Color, I see the wolf rendered properly. If I use the pass_Color, I see nothing on the screen.
This is what the screen looks like when I use out_Color in the fragment shader:
I know the diffuseReflection vector is full of 0's, by uncommenting this code in the vertex shader:
...
/*
float bug = 0.0;
bvec3 result = equal( diffuseReflection, vec3(0.0, 0.0, 0.0) );
if(result[0] && result[1] && result[2]) bug = 1.0;
diffuseReflection.x += bug;
*/
...
This will make the x component of the diffuseReflection vector 1.0, which turns the wolf red.
Does anyone see anything obvious I'm doing wrong here?

Answer 1

As suggested in the comments, try debugging incrementally. I see a number of ways your shader could be wrong. Maybe your normalMatrix isn't being passed properly? Maybe your in_Normal isn't mapped to the appropriate input? Maybe when you're casting lightSources.direction to a vec3, the compiler's doing something funky? Maybe your shader isn't even running at all, but you think it is? Maybe you have geometry or tessellation units and it's not passing correctly?
No one really has a chance of answering this correctly. As for me, it looks fine--but again, any of the factors above could happen--and probably more.
To debug this, you need to break it down. As suggested in the comments, try rendering the normals. Then, you should try rendering the light direction. Then render your n dot l term. Then multiply by your material parameters, then by your texture. Somewhere along the way you'll figure out the problem. As an additional tip, change your clear color to something other than black so that any black-rendered objects stand out.
It's worth noting that the above advice--break it down--is applicable to all things debugging, not just shaders. As I see it, you haven't done so here.