Simple shader example with of pointLight

@edapx wrote:

I'm quite confused regarding the behaviour of pointLight. I'm drawing a sphere and I'm applying a simple shader to it.

This is the setup of the scene

sphere.set(100, 100);
ofVec3f lightPos = ofVec3f(130,130,130);
light.setPointLight();
// see light docs http://openframeworks.cc/documentation/gl/ofLight/
// https://forum.openframeworks.cc/t/understanding-oflight/26230/3
light.setup();
light.enable();
light.setPosition(lightPos);

This is my vertex shader:

#version 150

uniform mat4 modelViewProjectionMatrix;
in vec4 position;
in vec4 normal;

out vec4 vPosition;
out vec3 vNormal;

void main() {
    vNormal = normal.xyz;
    vPosition = modelViewProjectionMatrix * position;
    gl_Position = vPosition;
}

and this is my fragment shader:

#version 150
uniform vec3 lightPos;
uniform vec4 materialColor;

in vec4 vPosition;
in vec3 vNormal;

out vec4 vFragColor;

void main() {
    vec4 color = vec4(materialColor);
    vec3 lightDirection = normalize(lightPos - vPosition.xyz);
    float dProd = max(0.3, dot(vNormal, lightDirection));
    vec4 colorWithLight = vec4( vec3( dProd ) * vec3( color ), 1.0 );
    vFragColor = colorWithLight;
}

The code works but as you see the reflection of the light looks wrong, the brightest part of the sphere is not facing the light

If I change the value of vPosition being passed to the fragment shader like this:

void main() {
    vNormal = normal.xyz;
    vPosition = position;
    gl_Position = modelViewProjectionMatrix * position;
}

The light looks correct

But now I'm passing the position of the vertext to the fragment shader without applying the model view projection matrix transformation, that feels weird.

I assume that when calculating the light direction:

vec3 lightDirection = normalize(lightPos - vPosition.xyz);

Both light position and vertex position has to be in the same coordinates space, but I do not know which is the way to go.

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